Recent Investigations in Faradic 
Electricity; 
Variation and Control of the Current by 
Rapidity of Interruption and Variation 
of Coils, and the Single-wire High- 
tension Current. 
GEO. J. ENGELMANN, M.D., 
ST. LOUIS, MO. 
BY 
From the 
American Journal of the Medical Sciences, 
December, 1893. RECENT INVESTIGATIONS IN FARADIC ELECTRICITY: 
VARIATION AND CONTROL OF THE CURRENT BY 
RAPIDITY OF INTERRUPTION AND 
VARIATION OF COILS, 
SINGLE-WIRE HIGH-TENSION CURRENT. 
AND THE 
BY 
GEO. J. ENGELMANN, M.D., 
SAINT LOUIS. 
PROFESSOR OF DISEASES OF WOMEN AND OPERATIVE MIDWIFERY, MISSOURI MEDICAL COLLEGE 
HON. PRESIDENT FIRST INTERNATIONAL CONGRESS OF GYNECOLOGY; LATE PRESIDENT 
OF THE SOUTHERN SURGICAL AND GYNECOLOGICAL SOCIETY ; OF THE ST. LOUIS 
OBSTETRICAL AND GYNECOLOGICAL SOCIETY : FELLOW OF THE AMERICAN 
GYNECOLOGICAL SOCIETY *, OF THE LONDON OBSTETRICAL SOCIETY ; 
OF THE BRITISH GYNECOLOGICAL SOCIETY, ETC., ETC. 
The American Journal of the Medical Sciences, 
December, 1893. 
FROM Extracted from The American Journal of the Medical Sciences, December, 1893. 
RECENT INVESTIGATIONS IN FARADIC ELECTRICITY: VARI- 
ATION AND CONTROL OF THE CURRENT BY RAPIDITY 
OF INTERRUPTION AND VARIATION OF COILS, AND 
THE SINGLE-WIRE HIGH-TENSION CURRENT. 
By George J. Ekgelmann, M.D., 
OF ST. LO«W" " 
I have been for years more or less interested in the therapeutic 
development of faradic electricity, but have as yet made no public 
mention of the interesting results achieved ; hence it is with pleasure 
that I can now not only present a resume of my investigations 
and experiments, but can demonstrate the practical results accruing 
therefrom—the new faradic apparatus—together with some of the novel 
physical and physiological results obtained thereby. With safety I 
may say that the therapeutic usefulness and adaptability of faradic 
electricity has been largely increased by the widely extended range and 
the controllability of interruption, and the defining and precising of the 
various secondary coils, as evolved by experiment directed toward the 
precising and controlling of the faradic current; the essential features 
from which all has branched being the rapidity of interruption and the 
character of the secondary coil. But whatever may have been achieved, 
and all that I can now show, although new in form, is merely a 
developing and perfecting of principles laid down in my first paper on 
“ Electricity in Gynecology,” read before the American Gynecological 
Society at its Baltimore meeting in 1886, and of axioms then outlined 
and clinically demonstrated. In that paper I called attention, first, to 
the importance of the variability of interruption and the determining 
of these interruptions; secondly, to the importance of differently con- 
structed secondary coils as necessities for the variation and perfect con- 
trol of the therapeutic effects of faradism ; and thirdly, to the necessity 
of precision in all the essential details for purposes of record, dosage, 
and comparison. I sought, in respect to faradic electricity, the same 
precision and possibility of record and dosage that had so rapidly 
advanced galvanism in professional favor as a therapeutic agent; and 
I believe that the points at that time aimed at have now been achieved, 
and that satisfactory results (may be confidently looked for. 
With the introduction of the galvanometer the constant current made 
rapid progress, but it is only within recent times that attention has 
again been given to faradic electricity, and such progress as has been 2 
ENG-ELMANJST : FARADIC ELECTRICITY. 
made lias been precisely in the lines mapped out in the paper above 
referred to. This will be better explained by giving an outline of the 
status of galvanic electricity then and now. It was not many years 
ago (at Baltimore in 1886), that I vainly attempted to procure a 
galvanometer in the city named for the purpose of demonstrating 
its use in therapeutic applications. Such an instrument could not be 
obtained until my esteemed friend. Dr. Wilson, by aid of the telegraph, 
succeeded in securing one from Mr. Fleming, in Philadelphia. It is 
probable that hardly a milliamperemeter was in use at the time; the 
galvanic current was vaguely and crudely applied. Now it has become 
an exact and well-defined agent of known therapeutic value. It was 
the galvanometer—the guide to precision, to dosage and record—which 
gave to galvanism its impetus and the confidence of the profession ; and 
it is this precision, this possibility of record and dosage, which is needed 
to place faradism upon its proper basis. 
But what was the status of the more variable sister to the continuous 
current, the more intangible induced, or faradic, at that time? Then, 
and for years thereafter—until Messrs. Waite & Bartlett produced a 
battery in accord with the suggestions made in that very paper toward 
the greater variation of interruption and coils—the ordinary sharp- 
current instrument with a single coil and a practically non-variable 
interruptor held sway and was used throughout. We must, of course, 
except the Tripier instrument made by Gaiffe, which, however, was used 
only by a few specialists, and was almost wholly confined to scientific 
laboratory experiments; and the Rockwell instrument, made by Kidder, 
with a secondary coil of different sized and lengthened wire, wound on 
one and the same spool and tapped so as to be used either singly or in 
series. This was the pioneer instrument in this country, and certainly 
the best. Such was what was known as “faradic electricity” in electro- 
therapeutics when I outlined what I deemed the essentials for progress, 
tbe very principles upon which the instrument now perfected is based. 
These principles I will quote from the paper already referred to: 
“ The effect of the current varies with the number of interruptions 
and with the nature of the helix, . . . with the length and thick- 
ness of the wire forming the secondary coil. . , . Sedative 
effects are best attained by the utmost frequency of interruption, 
and muscular effects by slow interruption. . . . A current of feeble 
tension and greater quality as developed by the short coil of thick wire 
has the best contractile effect on the muscle, and a current from a long 
coil of fine wire, a current of higher tension and less quantity, affects 
the muscle less and the nerve more.” 
To all this I still adhere, and I am gratified to see that these princi- 
ples are gaining ground and are bringing faradic electricity to the front, 
as is evident from the demand for improved instruments and the more 3 
EISTG-ELMANJST : FARADIC ELECTRICITY. 
general manufacture and use of instruments with well-regulated coils 
and interrupters; yet, while this is a great improvement, more still must 
be achieved. The best of these instruments, those made for Goelet and 
Hutchinson by the Galvano-faradic and the Chloride of Silver Battery 
Co., the Fleming instrument, and the Mackintosh imitation of the 
Gaiffe, as well as the earlier models of my own instrument made by 
Waite & Bartlett, approximate to some extent the desired conditions; 
but they lack the necessary range, precision, and controllability of in- 
terruption and coils. 
Faradism in its present status is incomplete and unsatisfactory as a 
therapeutic agent; and as the character, the quality, and the effect of the 
faradic current, quite contrary to the galvanic, depend entirely upon the 
producing apparatus, it is this which must be improved. Clinical expe- 
rience had told me that the rapidity of interruption and the character 
of the secondary coils were the essential elements, so that I sought to 
obtain in these factors the utmost range and precision. With such objects 
in view the new apparatus was constructed; it is the direct result of 
physical and physiological experiment based upon a knowledge of 
clinical needs and therapeutic demands, and substantially proves the 
correctness of the course pursued and the remarkable variation of 
current-effect which can be produced. 
I here refer to the instrument itself, because, as I have already stated, 
it is upon the apparatus that the quality and effect of the faradic cur- 
rent depend—unlike the galvanic, which is practically independent of 
the generator, currents from all sources being about the same. 
To give the induction current the necessary range and precision, it 
proved essential that the instrument be provided with : 
1. An adjustable, variable, and recordable interrupter of great range 
up to 50,000 or 100,000 interruptions per minute, with a motive power 
separate and distinct from that of the primary inducing flow. 
2. A series of secondary coils of definite quantity and electro-motor 
force, with great range, each adapted to a certain therapeutic purpose. 
3. An adjustable core, with scale to determine its position. 
4. The possibility of precise record of all details; this means a primary 
coil of known resistance and electro-motor force proportionate to current 
strength and secondary coils to be used, and a primary current of known 
intensity. 
I would strongly urge a uniformity or construction for core and primary 
coil, and uniformity of primary galvanic flow ; this would greatly facili- 
tate record and comparison, and could easily be accomplished, as most 
primary coils are very much alike, and there is no great variation in the 
galvanic force employed—from 2 to 6 volts and from 600 to 1300 
milliaraperes being generally used ; this is readily controlled by rheostat 
and galvanometer, and brought to the desired average intensity. 4 
ENGELMANN : FAEADIC ELECTRICITY. 
The new apparatus is constructed with reference to precision in all 
details, but it is the interrupter, with motive power separate and distinct, 
securing interruptions far more rapid than any hitherto obtained, and 
interruptions determinable in number, together with precisely defined 
secondary coils, which give the instrument its individuality, and I take 
pleasure in saying that the satisfactory result which has been achieved is 
due to the kindly manner in which Messrs. Waite & Bartlett have placed 
their efficient force and their material at my disposal; while the solving 
of practical problems, the practical carrying out of my ideas, I owe to 
Mr. Harry Waite, who has been my constant aid in all experiments 
made in this city ; therapeutic tests being constantly made in my clinic 
by my assistants, Drs. Ameiss and Temm. 
The interrupter. While the rate of vibration or interruption is one of 
the essential features of faradic electricity, it has hitherto been regarded 
merely as a necessary mechanical factor for the production of the current, 
of no therapeutic value whatsoever. Although variability is the very life 
and essence of faradic electricity, attention has never been directed to the 
importance of interruption in medical currents. Some vague references 
have here and there been made. Gordon, in his Electricity, briefly mentions 
a high-speed interrupter used for experimental purposes, but does not say 
what those experiments were, and, in fact, lays no further stress upon 
this fact. Dr. William Scheppegrell, of New Orleans, in a most pro- 
gressive publication which has just come to my notice, speaks of a 
similarly constructed interrupter as adaptable to galvanic and faradic 
currents, but gives no details as to any peculiarities of current, and makes 
no especial therapeutic claims for such current. Dr. William Hutchin- 
son is the first to speak of therapeutic effect, and in a paper read before 
the American Electro-Therapeutical Association in October, 1892, ad- 
vocates the singing rheotome, claiming interruptions of great rapidity, 
with astonishing anaesthetic effects; he unfortunately bases his meas- 
urements of speed upon aural comparisons with the tuning-fork—giving 
results which have not been fully borne out by my own investigations— 
and I may here say that I deem more positive tests of the rate of the inter- 
ruptions necessary than these, as few possess the delicate ear and the 
musical training necessary to make these comparisons ; but no matter 
what the speed possible, the rapidity of any vibrator so constructed can- 
not be controlled within a satisfactory range, nor can the necessary rate 
of vibration be secured whenever desired; any good features which it 
may possess are of no avail until it is used with a motive power separate 
and distinct from that employed for the coils. I deem it of less value 
for medical purposes, as its rate of interruption depends upon the strength 
of the therapeutic current to be used; hence rapid interruptions are out 
of the question where mild currents are to be employed, rapid interrup- 
tion necessitating strong currents. EXGEL MANX : FARADIC ELECTRICITY. 
5 
I must here express myself more fully upon this point, as I deem the 
separation of vibrator, or interraptor, from the induction coil itself essen- 
tial to the development of this form of electricity as a therapeutic agent. 
Hitherto the interrupter has been regarded as a mere mechanical factor, 
a mechanical necessity for the production of the induced current, and it 
has been in no way connected with therapeutic elfect; hence it has been 
a part of the apparatus, and will always be directly connected with it in 
the average coil for the sake of simplicity of construction and cheapness. 
In order to obtain the most satisfactory physiological and therapeutic 
results from the faradic current, the interrupter must be separate and 
distinct from the coils and propelled by a distinct motive power, for the 
following reasons: 
Changes in the primary galvanic current are necessary to control the 
rapidity of interruption, and this must be accomplished without affecting 
the physiological current from the coils, as changes in the primary flow 
supplying the coils must be accomplished without affecting the rapidity 
of interruption—all of which can be done onty by employing a separate 
motive power for each. 
For the purpose of properly actuating the vibrator, primary galvanic 
currents of too great an intensity have been used. 
Rapidity of interruption or alternation is a factor of large general im- 
portance, too long overlooked, which will yet claim greater attention, both 
for mechanical and for therapeutic purposes in connection with faradic 
electricity and with alternators and vibrators of other kinds. Mr. Tessla 
has demonstrated the marvellous mechanical results of rapid vibration, 
and D’Arson val revealed the surprising insensibility of the system to 
currents of extremely rapid alternation, and also proved their sedative 
effects. For physical, physiological, and therapeutic purposes, rapidity 
and variability of interruption and alternation are most important, and 
if it is true that the effect of the faradic current is mainly due to its 
mechanical influences upon the molecular constitution of the organism, 
the great importance of regulating that vibration is evident. That 
mechanical vibration is potent as a curative agent has been repeatedly 
proven, first in England, and interest in this subject is at present excited 
by the experiments of Charcot with the medecine vibratoire. Isolated 
cases have been published. Boudet, of Paris, cured facial neuralgia by 
the vibrations of a tuning-fork, 200 per second, communicated to a sound- 
ing-board upon which was fixed a small rod with ball end, which was 
placed upon the face at the point of exit of the infra-orbital, thus com- 
municating this vibration to the nerve. After an application of from 
five to six minutes the pain ceased for a time, and by continuance of the 
treatment a cure was achieved. In the Salpetriere a large tuning-fork 
was used, placed upon an extensive sounding-box, the atmospheric vibra- 
tions produced thereby acting as did the rod in the other case, and with 6 
ES GELMANN : FARADIC ELECTRICITY. 
similar satisfactory results, even to the restoration of muscular activity 
in the paralyzed lower arm of a hemi-ansesthetic. Varying rates of 
vibration have been successfully used by Dr. J. Mount Bleyer, of New 
York, in the treatment of diseases of the ear, and if there is any truth in 
the theory of the variation of molecular vibration as determining nerve 
disease and its cure by corresponding vibrations, the necessity of precisely 
determining the vibrations used is self-evident. 
But it is only to the interruption of the faradic current that I will here 
refer. The increased rapidity of these interruptions and the ability to 
control them render the application of effective currents possible to the 
most sensitive tissues, and give the greatest scope to the efficiency of 
those currents, especially increasing their sedative powers. The new in- 
strument gives us every variation of interruption ; we retain the vibrators 
as before used upon the Waite & Bartlett battery, but with a separate 
motive power of, at most, two Gonda cells; there is a single impulse 
key; the slow vibrator giving us up to 1000 or 1500 interruptions, and 
the rapid vibrator giving from 1000 to 3000 or 4000. These, of course, 
cannot be controlled Avith absolute precision, and precision Avithin such 
limits is hardly necessary, but if desired it can be attained by the ucav 
instrument, which gives us slow interruptions with absolute precision up 
to 400 per minute, and all the more rapid interruptions from 3000 to 
50,000 and 100,000 per minute can be obtained with a like precision. 
The interruptions are obtained from the commutator upon the axle of 
a small motor, and have been determined in number by the use of the 
speed indicator, Avhich is compared Avith the current intensity propelling 
it, the speed being governed with precision by the current used ; hence, 
after the preliminary experiments the rate of interruption, or the speed 
of the motor, is indicated either by the galvanometer or, Avhen a red-acid 
cell or storage battery of known force is used, by the rheostat. This 
instrument, however, serves not only as a controllable high-speed inter- 
rupter for these condary faradic current, but may be used as interrupter 
or alternator for the primary and for the galvanic current. I will here 
only speak of it as an interrupter in faradic electricity, and its impor- 
tance in this capacity will be appreciated after a brief review of some of 
the physiological experiments made Avhich demonstrate the great vari- 
ation of effect produced by variation of the rate of interruption. 
The effect of faradic electricity, best demonstrated by mild currents, 
sloAvly increases with the rapidity of interruption, as observed both upon 
motor and sensory nerves, up to 2500 or 3000 per minute ; then sloAvly 
decreases Avith an increase in the rapidity of interruption. The greater 
the current strength the greater the number of interruptions necessary 
to reduce or annul its effect completely, the muscle ceasing to respond 
before all impression upon the sensory nerve is lost. A moderate current, 
such as that from coil No. 3 of my battery (Waite & Bartlett) at 45 of the EXGEL MAY IST : FARADIC ELECTRICITY. 
7 
scale, or one-third of the coil in circuit, will produce muscular contrac- 
tions with from 45 to 100 interruptions per minute; this current grows 
stronger with an increase in the rapidity of interruptions up to 4000 per 
minute, then soon decreases. Muscular contraction ceases at 5000, at 
6500 its sensory effect is barely noticeable, and before a rapidity of 10,000 
is reached it ceases to be felt altogether. A very strong current, such 
as one from No. 3 coil completely overlapping the primary, with an in- 
ducing force of four Leclanche cells, and applied through large moist 
electrodes—in other words, a current too strong for therapeutic applica- 
tions with the ordinary vibrator at 3000 per minute, is barely perceptible 
with 25,000 interruptions per minute, and ceases to be felt altogether at 
28,000. The rapidity of interruption controls the physiological effect of 
the current as perfectly as the sledge movement of the secondary coil, so 
that, all other conditions remaining unchanged, it is an index of current 
strength which may well be utilized. The therapeutic value of rajfid 
interruption rests upon our ability to employ strong, efficient currents 
without discomfort, and is found in the nerve-quieting, sedative effects of 
these interruptions with fine coil currents. 
The coils. Therapeutic use having proved the variable effects produced 
by coils of different length and thickness of wire, my experiments were 
made on this basis: that quantity and electro-motor force of current, as 
determined by resistance or diameter of wire and number of winds were 
the determining factors, as far as physiological and therapeutic effects 
of the secondary coil are concerned ; and this has been proved correct, 
but the practical question remained as to the precise conditions under 
which currents of the greatest therapeutic value were produced, and 
under what conditions each special effect would best be obtained. Coil 
upon coil was wound as previous results seemed to indicate, and although 
still reserving final decision, I should now say that we have at least ap- 
proximated the physiological and therapeutic extremes. Motor, to the 
exclusion of sensory effect—that is, painless influencing of the muscle— 
is most satisfactorily attained by secondary coils of the lowest possible 
resistance with the largest possible electro-motor force or number of 
winds; by the heavy-wire coil, with a resistance of 0.7 or 0.8 of an 
ohm and 500 to 600 winds, of No. 15 wire, and better still by an in- 
crease in the electro-motor force by the use of fine wire in multiple—this 
being a coil of 6500 winds of No. 32 wire, with 4.1 ohms resistance. 
The opposite condition, that is, the highest possible resistance with the 
lowest possible electro-motor force, produces the most painful currents as 
used for purposes of counter-irritation—this is a coil of No. 40 wire, 528 
winds, and 180 ohms resistance. The utmost penetration, together with 
satisfactory general therapeutic effects upon the nerve, is obtained by 
coils of higher resistance and greater electro-motor force. Thus, a 
generally serviceable coil is one of from 4000 to 6000 winds and from 8 
ENGELMANN: FARADIC ELECTRICITY. 
250 to 740 ohms resistance; for sedative purposes, for the benumbing 
or amesthetic effects, a still higher electro-motor force is necessary, as in 
a coil of 9000 or even 12,900 winds and 2500 ohms resistance. 
To better illustrate what these figures mean, I will say that the longest 
coils heretofore made for medical instruments have, in the best, been of 
3500 to 4000 winds, or 2000 feet, and good vibrators gave 3000 inter- 
ruptions per minute, or 50 per second. 
Such have been the results obtained after careful experimentation with 
coils of the most various kinds. We have seen that low resistance with 
high electro-motor force is the coil most effective upon muscle, causing 
least sensation ; and the highest resistance with the lowest electro-motor 
force is the very opposite—is the most intensely nerve-irritating coil with- 
out muscle effect; while the penetrating motor and sensory effects, varied 
by the character of application, are produced by an increase of both resist- 
ance and electro-motor force, sedative effects being best produced by the 
highest possible electro-motor force. But I believe that a limit is to be 
placed to this, at least when used in connection with the ordinary bat- 
tery force and primary coil, and that this need certainly not exceed 9000 
or 10,000 winds. 
From all clinical and physiological experiments it is evident that the 
quantity and electro-motor force of the current, as indicated by resist- 
ance and by the number of winds, are the determining factors ; hence an 
instrument can be of value only when these data are given, and given 
with precision ; coils must be accordingly marked, just as the dosage is 
indicated for any other remedy, and for purposes of record and comparison 
these points must be referred to. For the sake of comparison, it would 
be preferable that certain standards should be adopted, yet as this is 
almost impossible, each manufacturer advocating his own special instru- 
ments, these instruments should at least be precise, with definite and 
clearly indicated qualities. 
It would seem needless to insist upon the use of properly constructed 
coils, such as best serve the purpose intended to be accomplished, and 
yet attention must be directed to this point, as some still claim all effects 
from one and the same coil, or from one and the same coil tapped at 
different points. It is, indeed, true that varying effects can be obtained 
from one coil by varying the method of application, but by no means 
so distinctly and so satisfactorily as by a variation of coils; in short, 
such results are primitive, partial, and incomplete. Each of the coils 
I have selected answers a definite purpose, best attaining the desired 
effect without complication by other unnecessary and often deleterious 
action. 
The coil of 4.1 ohms resistance and 6500 winds contracts the muscle 
thoroughly without influence of any kind upon the nerve, and the coil 
of 180 ohms resistance and 528 winds produces a painful counter-irrita- ENGELMANN; FARADIC ELECTRICITY. 
9 
tion without any effect upon the deeper tissues ; and nothing demonstrates 
more strikingly the great importance of resistance or diameter of wire 
upon the physiological effect of the current: this coil gives a painful 
current and does not in the least affect the muscle, whilst a coil of 0.85 
of an ohm resistance and 528 winds gives a current which is hardly appre- 
ciated by the sensory nerves, but acts well on muscular fibre; and this 
striking contrast may be observed with the same number of winds in 
circuit, or precisely the same electro-motor force. It needs but the testing 
to prove the necessity of coils so varied for the satisfactory use of 
faradic electricity in medicine; hitherto it has not been a very useful 
agent, for the reason that our apparatus has been imperfect and we 
have lacked the means of developing the most valuable feature of this 
form of electricity. 
Actual galvanometric measurement of the secondary faradic current 
in micro-coulombs is possible, but is no indication whatsoever of physio- 
logical effect, hence useless for the physician and useless for record and 
dosage. Until greater progress is made we must refer to the following 
data in lieu of direct measurement: a. Strength of the primary galvanic 
inducing force, b. Character of primary coil. c. Position of core. 
d. Number of winds and resistance of secondary coil and its position 
upon the scale in reference to the primary, e. Number of interruptions. 
/. Character and location of electrodes, g. Duration of seance. This 
record is possible only with precise, well-authenticated instruments, and 
instruments in which the motive power controlling the interrupter is 
independent of that used for the coils. 
In conclusion I may say that by means of this increased rate of inter- 
ruption and a greater variation in secondary coils, the therapeutic possi- 
bilities of faradic electricity have been greatly extended ; and by the 
exact determination of the rate of interruption, with the character and 
position of the secondary coil—the character of secondary coils being 
determined by their resistance and the number of winds—compari- 
son, record, and dosage are possible. Not only can we attain a great 
variety of therapeutic effects by the proper combination of the various 
essential factors, but as these can all be defined and determined, dosage 
and record are approximated to such an extent that with instruments 
properly constructed and precised, satisfactory work will be possible 
and faradic electricity will assume its proper place as a therapeutic 
agent. 
The single-wire high-tension current is one of the products of the 
induction coil which is, perhaps, of greater interest experimentally 
than of value therapeutically, yet I will take the opportunity of demon- 
strating curious phenomena which have developed from Mr. Harry 
Waite’s suggestion of grounding one pole. The negative pole of the 
break current being the most intense, this is used, and the positive 10 
ENGELMANN: FAEADIC ELECTRICITY. 
grounded; a high-tension current is thus obtained, even at quite a dis- 
tance from the generator; it is similar to the static, and produces some 
curious effects. This current is more like a pure static than like the 
so-called static induced. 
While there may be little therapeutic use for the high-tension single- 
wire current, it is nevertheless worthy of trial, and I desire to call atten- 
tion to it as useful in neuralgic conditions; and applied by the hand of 
the operator in the various forms of headache and in the giving of 
massage, marked physiological effects have been observed, but I am 
not as yet in a position to demonstrate their therapeutic powers. 
The mechanical effects are shown by the glow of the incandescent lamp 
and by the spark, which is like the static; a small electric lamp, such 
as is used for laryngeal purposes, or a 118-volt incandescent lamp, may 
be set aglow twenty, thirty, and more yards away from the apparatus, 
by contact with the negative pole, if the glass bulb of the lamp be held in 
the hand of the operator, it being indifferent whether or not he be upon an 
insulated platform ; it will likewise glow if he pass the current through 
his body, seizing the negative wire in his hand and grasping the metallic 
base of the lamp in the other, then approximating the glass bulb to 
some other individual. While this is the carrying of the current by 
means of a single wire, it is a pure induction effect, and not like those 
startling results obtained by Mr. Tessla—dependent upon rapidity of 
vibration, unless it be molecular. The glow will be produced as a mo- 
mentary flash by single contact; as contact is more rapidly made, as 
vibration or interruption succeed each other more rapidly, even at from 
500 to 1000 per minute, these successive flashes merge into a constant 
glow, a glow which varies with each individual lamp: in some it follows 
the carbon filament, or centres upon that part of it nearest the fingers 
or hand grasping the glass bulb; in others it is independent of the fila- 
ment, as a diffuse glow, but most frequently more intense toward the 
grasping fingers. Different lamps of the same voltage act very differ- 
ently, probably owing to the different conditions of the vacuum—its more 
or less perfect state; so also is the effect a different one, whether the 
vibrator of the coil itself is used or whether the separated interrupter is 
employed, which gives no flash on single contact, either make or break, 
and does not produce the glow until a rapidity of from 8000 to 10,000 
per minute is obtained. This reaches its height at from 10,000 to 15,000 
interruptions per minute, decreasing as these grow more rapid. These 
effects were produced by a red-acid or Grenet cell. Only carefully 
wound, well-insulated coils can be used, by reason of the extremely high 
tension of the current—which, on a damp day, will throw a spark of 
one-third of an inch. The most satisfactory results were obtained from 
a coil of high electro-motor force, 9000 winds of No. 36 wire ; both physi- 
cal and physiological effects diminished with an increase or decrease of 11 
ENGELMANN : FAEADIC ELECTRICITY. 
electro-motor force, and are barely noticeable from coils with as few as 
4000 winds, or with as many as 13,00 c).1 
The spark produced in damp weather has quite an effect through high 
resistance. From the point of a metallic electrode it is painful, and acts 
intensely upon motor points, but the skin must be very dry. When 
applied by means of the entire hand, to the forehead, for instance, no 
sensation is produced, and yet a physiological effect is undoubted, so 
that this must prove a satisfactory method of therapeutic application, as 
any degree of sensation can be produced by a lessening of pressure until 
the surfaces are barely in contact. 
Mild, general applications of this high-tension single-wire current have 
a marked constitutional effect, as became evident from the similar con- 
ditions experienced by all engaged in these experiments, and repeatedly 
experienced. A weariness, a relaxation, with nervousness in some, was 
followed by a healthy tire and refreshing sleep. The ordinary metallic 
electrode touched lightly to the motor points, with slow vibration, 80 to 
100 per minute, contracts the muscle forcibly, and without pain ; 500 
to 1000 vibrations per minute are more painful. The rapid vibrator, 
3000 per minute, gives a softer current, the sensation in all cases disap- 
pearing with a firm pressing down of the electrode. 
I have cited these high-tension single-current effects from high volt- 
age coils of the faradic apparatus on account of the physical facts 
which they demonstrate, and for the purpose of indicating therapeutic 
possibilities. 
The peculiarities of opening and closing current, of positive and 
negative pole, of varying rates of interruption, and of difference in coils, 
are all marked in the high-tension current; the flash on single contact 
is observed only in the opening, not in the closing current, as the pre- 
dominance of opening over closing current, which increases with increase 
of resistance, is very great with this high resistance; the predominance 
of the negative over the positive pole is likewise strikingly evident; the 
light, like the physiological effect, increases with the rate of interruption 
to a certain point, and then decreases ; so likewise does the effect increase 
with an increase of the electro-motor force, or the number of winds in 
the coil, attaining a maximum with a certain relation of electro-motor 
force to resistance, then again to decrease as electro-motor and resist- 
ance increase still more. 
In the glow of the lamp we see the fact well demonstrated that a cer- 
tain phase of current, a certain coil, within given limits of the electro- 
motor force and resistance, is necessary to determine a certain effect. 
1 As one coil of 13,000 winds has produced intense single-wire currents, I cannot he positive 
upon this point ; and these coils demand such careful winding and insulation that they are 
not always fitted for high-tension experiments; this was with a resistance up to 2500 ohms ; 
with lower resistance a higher electro-motor force could be utilized, i. e., if heavier wire be 
used, and the result would be much more intense, as we find it from the Ruhmkorff coil. 1 2 
engelmann: faradic electricity. 
Precisely so is it with the coils needed for motor and nerve effects. We 
also see that a certain rate of vibration best produces the light effect, 
as definite rapidities of vibration are most effective for different 
physiological effects. 
Therapeutic possibilities only can be indicated, as there is hardly suf- 
ficient intensity in the single-wire currents as obtained from the ordinary 
medical battery, even with 9000-wind coils, to produce very marked effects, 
and these are dependent to a considerable extent on the weather. To 
produce always reliable and efficient currents of this kind, we must 
have a stronger primary galvanic flow, and coils of higher electro- 
motor force, with less resistance, than is possible from the small spools of 
the medical instrument. 
I was highly elated at the result of our first experiments, which hap- 
pened to have been made under extremely favorable conditions, but soon 
found that these could not be relied upon, so that I would now be less 
sanguine in the hopes of therapeutic success ; and yet this current merits 
consideration and trial. It is certainly of interest in its physical features. 
3003 Locust Steeet, St. Louis.