01ST A NEW 
METEOROLOGICAL INSTRUMENT. 
By J. W. OSBOENE, 
OF WASHINGTON, D. C. 
[From the Proceedings of the American Association for the Advancement of Science, 
Detroit Meeting, August, 1875.] J f. Sf -y ' r . , On A New Meteorological Instrument. By J. W. Osborne, of 
Washington, D. C. 
The study of Meteorology has always possessed great attrac- 
tions for those investigators who desire rapid practical results for 
the aid and benefit of mankind. 
Of scientific men there has been a large proportion, both 
workers and theorizers, who have labored in this field; but it is 
chiefly of late years that great and important advances have been 
made. Not only have the means of observing atmospheric phe- 
nomena been improved, but the observations themselves have been 
systematically extended over vast tracts of country, and have, by 
the help of the telegraph, been collected with such rapidity, as to 
greatly increase their scientific as well as practical value. Great 
results have been the legitimate consequence of the large expendi- 
tures of labor and money which such records demand; results 
which have been appreciated by the general public, and still more 
thoroughly by scientific men; and which would now be very 
unwillingly dispensed with by either class. But it will be seen 
that these facts, however valuable and important, are all of an 
essentially objective character. We are informed both for the 
past and future respecting atmospheric pressure, and temperature ; 
of the direction and force of the wind ; of the relative quantity of 
moisture present, and of the amount of rain,— in a word, of all the 
available facts, external to the earth we stand on, and to our own 
bodies, which scientific and material resources can supply. These 
things have a bearing upon our comfort and prosperity ; they affect 60 
A. MATHEMATICS AND PHYSICS. 
us as merchants, traders, agriculturists and manufacturers; and 
the information is conveyed in a form directly applicable to our 
wants ; but we do not, procure from such statements, any distinct 
or precise knowledge of the manner or the degree in which they 
affect us personally. 
It is hardly too much to assert that, at the present day, after 
years of laborious research, the meteorologists furnish no data from 
which it is possible to deduce the subjective character of any 
given climate, or its effect upon the human body. We might go 
farther and say —of life upon the face of the earth. 
This is certainly true if we seek for a numerical expression 
which shall make possible the comparison of the climate of one 
place with that of another ; or of the same place at different times 
of year; or the climate of indoors with that of the open air; for 
we cannot grasp in a single expression the several meteorological 
elements affecting us, referred as each is to a totally different unit 
of measurement. Considerations like the foregoing have caused 
me to attempt the construction of an instrument which would fur- 
nish the information sought, or such an approximation towards it, 
as would add definitely to our knowledge, and lay a foundation for 
future developments in this direction. 
Confining myself at present to considerations affecting the 
human body, I will preface the description of the instrument itself, 
by drawing attention to the following facts. 
If an effort is made to realize the nature of the influence which 
the elements exert upon the body of a man, it will appear that the 
prominent and leading effect they tend to bring about is a change 
in his temperature. This, for certain of the meteorological ele- 
ments, may be either a raising or a lowering of the bodily heat; 
but taken together, their joint and total effect must tend at all 
times, and in every habitable climate, to dissipate and reduce the 
normal heat of the body. 
If this were not so, the oxidation within the organism would 
cause an increase in the temperature of the blood and viscera, 
thereby establishing a state of things inconsistent with health, and 
with life itself, for any length of time. It must not be lost sight 
of, therefore, in considering this subject, that the body of a living 
healthy man is a mass of hot matter, cooling, and having its lost 
heat perpetually supplied by physiological changes, in quantity 
sufficient to maintain a uniform thermal standard of about F A. MATHEMATICS AND PHYSICS. 
61 
And, whatever the causes of this loss may he, we say when it is 
rapid that the weather is cold, and when slow that it is hot. In 
the one case, the functions are called upon to make up the deficiency 
rapidly, and in the other to facilitate the dispersion of the body’s 
superfluous and injurious warmth. 
The temperature, as shown by the thermometer, is very com- 
monly, I might almost say universally, accepted, as indicating the 
thermic influence acting upon us, and we speak of its readings as 
if they expressed in some way the sensible temperature with which 
the living organism has to deal. That this is an error, and a very 
pernicious one, a moment’s reflection will serve to show. The day 
is hot and oppressive, if, at 80° F., the air is damp and still; 
while with a breeze and dry atmosphere, it is fresh and pleasant. 
Or, if in winter the thermometer fall to 20° F., no inconvenience is 
felt so long as it is perfectly still; but should it blow hard, then 
the cold will be almost unendurable. 
Accordingly, what I shall call the physio-thermal effect, appears 
to be the joint result of several influences, acting simultaneously, 
each affecting in variable degrees, and often in contrary ways, the 
rate at which the body cools. 
The three great factors which together determine the sensible 
climatic heat, are the temperature of the air at the time ; the rela- 
tive amount of aqueous vapour present; and the force or velocity 
of the wind. The first acts by accelerating or retarding, and 
sometimes altogether neutralizing radiation from the hot human 
body. The second, that is the moisture, promotes or hinders 
evaporation from the skin and lungs, in variable degrees, deter- 
mining in like proportion the consequent loss of heat. The wind 
acts in two ways; first, as a convector, it removes from the body 
with greater or less rapidity the warmed film surrounding it, 
bringing cooler air in its place to be warmed up again in its turn; 
this action being of course reversed in those cases where the exter- 
nal temperature is above F.: and secondly, for a similar 
reason, the wind acts in all cases as a promoter of evaporation 
(except when perfectly saturated with moisture at or above the 
temperature of the surface of the body), the refrigeration bearing 
some relation to the rate at which it travels. 
The problem I have sought to solve then is, to furnish means by 
the help of which we may express numerically and comparably 
that which hitherto has been left to vague conjecture and state- 62 
A. MATHEMATICS AND PHYSICS. 
ment, namely: the aggregate of the physio-thermic influences 
which affect the living human body at any particular time and 
place. 
Without going into minute details, the instrument I have in- 
vented is constructed as follows. 
A pole, or standard about six feet high, made of a strong brass 
tubing, is held upright by a heavy foot or base. 
At right angles from this, and in the same direction, three arms 
or brackets extend. These, while they slide up and down on the 
standard, can be clamped at such places as suit the height of the 
observer. 
The middle bracket is nine or ten inches long, and carries at its 
outer extremity a horizontal cylindrical ring of thin brass about 
four inches in diameter. 
From the lower edge of this ring, and held fast to it by a strong 
rubber band or clamp-ring, there hangs a cylinder made of “ bond,” 
or bank-note paper. This cylinder is exactly 100 millimetres in 
diameter, and 150 long. It is made upon a turned mandrel, and 
closed up the side by the use of a thick mucilage of albumen, 
dried, and then coagulated by immersion in wet steam. This 
method gives a very narrow, strong seam, which absorbs water 
like the rest of the paper. 
Into the open bottom of the paper cylinder a very thin disk of 
brass is fitted, and held there by a second rubber band or clamp- 
ring. 
The vessel so constructed is intended to hold water. The paper 
which forms its walls can be removed and replaced at any time, 
without altering its capacity, or the relation between its bulk and 
surface. The upper edge of the brass ring, from which the paper 
cylinder hangs, is provided with a flat brass cap. Through the 
centre of this a short tube or socket extends. This revolves in 
the cap, fitting into a suitable bearing for that purpose. It termi- 
nates above in a small horizontal pulley, with a hole through its 
centre, while to its lower end an agitator is attached. 
The agitator consists of a narrow strip of thin metal formed into 
a spiral, which makes four revolutions from the top to the bottom 
of the cylinder. When this is made to rotate, it sweeps the inside 
surface of the paper cylinder, but without touching it. From the 
brass disk below, three vertical stationary blades, placed radially, 
rise to the level of the top edge of the paper. These blades leave A. MATHEMATICS AND PHYSICS. 
63 
still an unoccupied space in the centre of the cylinder; and be- 
tween their outer edges and the paper, the spiral revolves freely. 
The object of the blades is to hold the water contained in the 
cylinder from revolving, so that the spiral, when in motion, may 
cause a constant current down the inside surface, and up the centre 
of the cylinder. The lower of the three brackets carries at its 
extremity an upright, adjustable, slender pin of wood, which fits 
easily into a little projecting socket attached to the centre of the 
under side of the disk, which forms the bottom of the cylinder, 
and prevents the paper suffering from lateral impulses given it by 
the wind, or when it is being moved from place to place. 
The upper bracket carries a thermometer on its outer end. This 
is exactly over the axis of the cylinder, so that when it is lowered, 
the bulb, which extends seven or eight inches below the scale, 
passes through the horizontal pulley and short tube connecting it 
with the agitator, and takes its place in the centre of the mass of 
water, in which position it is clamped. This thermometer is pro- 
vided with a centigrade scale. Its tube is ground flat, and pol- 
ished on two opposite surfaces parallel to the ribbon of mercury. 
The scale to which it is attached is pierced by a narrow slit which 
extends from zero upwards to 100°. By this means I succeed in 
getting rid of the reflection from the cylindrical surface of the 
tube, and can watch the column of mercury as it appears projected 
against a little white screen adjustable behind the scale. A. sliding 
cross hair parallel to the lines of division on the scale, and sup- 
ported about an inch in front of the latter, is also used to fix the 
position of the eye when reading, and so avoid parallax. This 
slide is connected with a long screw at the side of the scale, by 
revolving which it can be placed and held in any required position. 
For very exact readings a microscope with cross hair is also 
employed, which then takes the place of the simple slide just de- 
scribed. 
A clock-work, attached to the standard below the brackets, im- 
parts motion to a small silken belt which runs upwards in a verti- 
cal plane as far as the middle bracket, where two little rollers give 
it a lateral direction, so as to drive the horizontal agitator-pulley, 
and thereby keep the contents of the cylinder in a thoroughly 
mixed -and moving condition, that the temperature of any part 
may be always that of the whole. 
Below the clock-work a vessel of thin brass is supported by a 64 
A. MATHEMATICS AND PHYSICS. 
short arm. This is somewhat larger in size than the paper cylinder ; 
it fills a double purpose, acting as a covering for the cylinder when 
not in use, and receiving the overflow water from it in a manner 
to be presently described. 
A fourth bracket or arm, wdiich may be regarded as supple- 
mental to the instrument proper, is clamped at a convenient 
height on the central standard. It extends in an opposite direc- 
tion from the other three, and carries the ordinary wet and dry 
bulb thermometers, and a stop watch with a spring-back second 
hand.1 
Lastly ; a high copper vessel called the filler, holding about two 
quarts of water, with a long curved spout tapering down to ] inch 
diameter, is used for filling the cylinder with hot water. 
This filler is furnished with a cover, and a wooden handle oppo- 
site the spout; it is also provided with a thermometer which 
is slipped into a small dry tube extending from the top obliquely 
towards the centre of the vessel, so that while the water in it is 
heating on a gas stove, its temperature can at any time be ascer- 
tained approximately. 
I proceed now to explain the way in which observations are 
taken with this instrument. The cylinder above described is a 
porous vessel. Its bond paper walls are slowly permeable to 
water, so that without appearing wet on the outside, they offer 
to the air as much moisture as it is capable of taking up; that 
which is lost being quickly replaced by capillary action. Experi- 
ment so far has shown this to be the case, except when the 
evaporation is very excessive indeed. The bond paper by its 
strength, aqd the purity of its composition, and from the fact that 
it can be obtained of perfectly uniform character, is admirably 
adapted for this purpose; and when wet it looks and feels very 
like an animal membrane. I know of no material of constant 
quality, and one which could be made into a vessel of a definite 
and fixed size, that would answer as a substitute for it. 
If the suspended cylinder so constructed be filled with water at 
the temperature of the blood, it will be seen that its condition is 
similar to that of a man who has lost the power of generating 
iln the drawing which accompanies this paper, two stop-watches are shown 
instead of one, by which the timing of sequent intervals is much faciliated. Both 
watches are connected by a brass strap in such a way that the movement which stops 
one starts the other instantly. The spring-back arrangement is independent of this, 
so that each reading is made from zero, with plenty of time for its exact registration. A. MATHEMATICS AND PHYSICS. 
65 
heat. Both ■will instantly begin to fall in temperature. Now if 
we could ascertain the time in which the man’s body fell one de- 
gree, we would be justified in assuming that when he was in the 
normal condition he would have had to make the same amount of 
heat in a like interval, inasmuch as he always has to make exactly 
what is lost. 
Strictly speaking, a little more would be demanded of him, 
because the hotter his body is, the more heat he will lose in a given 
time. For very small increments however, this difference may be 
neglected, and I will not at present discuss it. 
This interval of time then, would express the demand upon the 
system, the intensity of the physiological action necessary to sus- 
tain the body in a state of health ; and it would also be a measure 
of the climate at that particular time and place, subjectively con- 
sidered. As such a determination for the actual man is impossible 
at present, I endeavor to obtain a comparable result from the cyl- 
inder. Assuming it to be full of cold water, as is generally the 
case, its temperature is raised by slipping a piece of small 
rubber tubing over the spout of the filler, the contents of which 
have been previously heated several degrees above blood-heat, 
and attaching the other end of it to a little conical tube which 
passes through the thin brass disk, forming the bottom of the 
cylinder. This tube is flush on the inside, and is closed there by a 
small flap of thin rubber, so that the water cannot flow outwards. 
By raising the filler above the level of the top of the cylinder, the 
hot water lifts the valve and enters. As it rises,-it fills a small 
siphon tube, which passes through the side of the brass ring from 
which the paper hangs, and then flows off through a rubber tube 
to the overflow vessel, near the foot of the standard, which has 
been already described. 
At the commencement of this operation the clock-work is set 
in motion, whereby the agitator is made to rotate, and establish 
so perfect a mixing of the hot and cold water as to cause the 
temperature to rise gradually and steadily; the addition of hot 
water can then be checked, and the rubber tube removed, at any 
particular position of the mercury. After this has been done, the 
siphon still continues to act, until the water is finally cut off ex- 
actly at the upper edge of the paper, by which the quantity of 
water in the cylinder is always precisely the same. 
Having raised the temperature of the whole mass of water dis- 66 
A. MATHEMATICS AND PHYSICS. 
tinctly above blood-heat (37° C.), and letting the agitator continue 
uninterruptedly, the observer waits till the mercury falls to 37° C., 
when he starts the stop watch, and counts the time in seconds 
which each degree takes to fall, till he has obtained a series suffi- 
ciently long to give the character of the descent, and render a re- 
duction to a single expression possible. In summer weather about 
six readings will probably be found sufficient; in winter a greater 
number may often be desirable. The whole interval which elapses 
from first to last, should be long enough to allow of several repeti- 
tions of the cycle of fluctuations in the thermic influences, which 
the observer will soon recognize, so that an average result may be 
had. When a series of this kind is made under constant condi- 
tions (as for instance in a closed room) a perfectly smooth and 
regular curve will be the result; but this is not easily obtained, 
because of the difficulty of maintaining such conditions perfectly. 
In the open air the changes in the velocity of the wind invariably 
give rise to irregularities with which the mathematician will have 
to deal. These irregular oscillations coincide exactly with the 
gusts of wind, and the comparatively still intervals between them ; 
they coincide also with the observer’s sensations of coolness and 
warmth. 
The general character of these curves is much influenced by the 
position of the wet bulb temperature in relation to 37° C. When 
these are near each other, the cylinder will cool slowly, and the 
curve will be flat; when the temperature of evaporation is low, 
the fall will be rapid, and the curve proportionately steep. That 
this must be so will be recognized at once, when it is remembered 
that the ordinate coinciding with the temperature of the wet bulb 
must be regarded as an asymptote to the curve. 
No earnest attempt has yet been made to determine the equa- 
tion of these curves. Indeed there has not been time, nor a suffi- 
cient number of satisfactory observations made under constant 
conditions ; but as an expedient for present use and instruction, 
I devised the following method, by which to obtain comparable 
reductions which should furnish values proportional to each other. 
If, under constant influences we extend the readings upwards 
from 37° C., beginning to time the fall of the thermometer at say 
60° C., we shall find that the curve at such high temperatures differs 
very little from a straight line. 
If we regard it as such, and select say 50° C., as the point of A. MATHEMATICS AND PHYSICS. 
67 
comparison, we shall obtain readings from which it is easy to 
eliminate the irregularities due to wind, or any other intermittent 
causes. Thus, if the day is very warm the observer begins to 
time the descending mercury at 53° C., and counting till it reaches 
3° below 50, namely 47° C., he divides the total number of seconds 
by 6. This interval in the hottest and most sultry weather will be 
about 5 minutes. If the day is cooler, judging by his feelings, 
the observer may fix on 4° above and 4° below dividing by 8 ; if 
quite cold 10° above, and 10° below, and even double that will not 
be too much, always aiming at a total interval of about 5 minutes. 
It will be seen that the colder the weather is, the more nearly 
will the curve about 50° C. approach a straight line, and the 
further below that temperature will it retain the same character, 
so that the error will not increase with the longer distance travelled 
by the mercury. This method is based upon the assumption that 
the ordinates of the normal curve are proportional, and that an 
arithmetical mean will therefore reduce them, however irregular, 
to a single expression. 
It may be urged that results so obtained are disassociated from 
the blood temperature with which we started ; but it should not be 
forgotten that we do not aim to get absolute, or even relative 
values. The great difference in men’s weight, and surface in rela- 
tion to their weight; in the amount of clothing they employ; in 
their habits of body, and in many other ways, renders that impos- 
sible. All we can hope for are results which shall be themselves 
proportional, and comparable only as regards the average man. 
With this in view one temperature is theoretically as good as 
another, although in the practical use of the instrument, and in 
the application of corrections, which have yet to be investigated, 
a judicious selection may be made. Nor should it be thought that 
I regard the observations at high temperatures, as replacing the 
series at low ones, which give us the special character and fluctua- 
tions of the thermic influences. The latter are of the greatest 
importance, and throw much light both on the nature of the 
climate, and on the physiological power of resistance to its influ- 
ence, which the body is called upon to exert. In this connection 
it may be well to say something of the dimensions given for the 
present to the cooling vessel. Numerous experiments have been 
made with cylinders of different capacity, and with large differences 
in the relation of mass to surface. The result reached appears to 68 
A. MATHEMATICS AND PHYSICS. 
be tolerably satisfactory and serviceable ; but it cannot be regarded 
as fixed ; nor is it possible by a priori reasoning to establish any 
size as the best. The conditions to be kept in view are, first; 
To see that the rate of cooling is not disproportionately influenced 
by any one of the three factors. Second: to give the cylinder 
sufficient mass to ensure readings of suitable duration. Third: 
to make the instrument as a whole convenient and manageable, in 
a mechanical sense. To discuss this subject fully, more informa- 
tion is required than I possess at present. 
Having done something towards arriving at a knowledge of the 
aggregate of physio-thermic influences which the temperature of 
the air, its moisture, and its motion jointly exert; our next effort 
should be to analyze that aggregate, if possible, and apportion to 
each factor its share, positive or negative as the case may be, in 
the abstraction of animal heat. 
If we observe with two cylinders at the same time, which are 
identical in every respect, save that one is pervious, and the other 
impervious to water, the results will differ, that from which there 
is no evaporation taking longer to cool than the other. This 
difference will express the value of the aqueous vapor present, as 
a cooling agent. 
If simultaneous observations are made with two instruments, 
one exposed to the full force of the wind, and the other sheltered 
from it, but otherwise under the same conditions, we shall in like 
manner get an expression of the thermic influence referable to 
the wind, both as a convector and as a promoter of evaporation. 
If both cylinders are impervious to water we shall again elimi- 
nate evaporation and obtain the cooling effect of the dry air in 
motion. 
If from the aggregate effect of all the factors, we now deduct 
that due to the moisture, and to the wind, the remainder will be 
the thermic influence ascribable to the actual temperature alone. 
There may be, and doubtless are, many and serious difficulties 
to be overcome in making these determinations ; but that the 
knowledge I have indicated in the foregoing, will eventually be 
obtained, there is little doubt, as there can be none of its great 
importance and value to mankind. 
One step more it will then be fair to demand ; I mean the dis- 
covery of empirical formulae, by which meteorological observations 
already made and recorded may be converted into expressions of A. MATHEMATICS AND PHYSICS. 
69 
thermic influence. In this way a vast flood of light will be quickly 
thrown on questions relating to the influence of climate on condi- 
tions of health and disease; development and decay; mental 
energy ; and subjects of like immediate personal interest. 
To speak of results at this time, and obtained from an instru- 
ment but a few months in existence, would certainly seem prema- 
ture ; and yet some things have been so forcibly presented to my 
mind, that a very short statement of them may be permitted. The 
consecutive, outdoor observations I have made consisted of two 
daily, at 7.35 A. M., and at 4.35 P. M., synchronous with those 
of the signal service observatory. These have been prosecuted 
for a little more than two months. 
The deductions which they certainly justify are as follows : 
1. That the sensible temperature affecting us departs widely from 
the actual, obtained from the thermometer. 
2. That the fluctuations in it are infinitely greater in amount 
than most of us have any idea of. 
3. That besides the great changes from day to day in the mean 
sensible temperature, we have what may be called instantaneous 
oscillations, also very considerable in amount, and scientifically 
all but unknown. 
4. That the wind very often plays a more important part in 
determining the sensible temperature than the actual temperature 
itself. 
5. That the instantaneous oscillations are almost solely due to 
fluctuations in this meteorological element. 
The first statement I have already illustrated by an example, 
which might be supplemented by a multitude of others ; for nothing 
is more common, while the thermometer is always quoted as 
something which cannot err, than to hear people praise or blame 
the weather quite irrespective of the teachings of that instrument, 
and often in direct contradiction to them. We use in fact in 
ordinary conversation a number of phrases which show the neces- 
sity in the popular mind of qualifying the information furnished by 
science. We speak of hot weather as sultry, close, heavy, dull, 
muggy, and clammy; or as fresh, pleasant, and clear. Of the 
cold days as raw, bitter, or damp, and also as fresh, bright, and 
invigorating. 
We describe a locality as exposed and bleak; or as sheltered 
and warm. A house as drafty; a street as “shut in.” We say 70 
A. MATHEMATICS AND PHYSICS. 
that not a breath of air is stirring; meaning really that we feel 
the want of some cooling agent, and for relief we fan ourselves to 
“get air.” All such qualifying words give vague expression to 
phenomena which figures do not reach. 
With regard to the wide range of the sensible temperature it 
may be said that the difference in the rate at which we lose heat, 
on a still, hot, and moist day in August or September, and on a 
cold one in midwinter, with the mercury below zero, and a gale of 
wind blowing, is very great indeed, subjecting the bodies of all 
exposed animals to extremes of heat and cold of which the physi- 
ologists have taken but little account. Still less have they recog- 
nized the existence of instantaneous oscillations. As we sit in 
our rooms, every breath of air which enters lowers the sensible 
temperature, and every moment of calm raises it immensely; an 
incessant rise and fall which may take place several times a minute. 
To illustrate the importance of the wind as a thermic agent, the 
assertion may be ventured, that there are many wet, stormy climates, 
such as that of Ireland, where it scarcely freezes, that will be 
found, so far as our bodies are concerned, to approach the still, 
cold climate of the icy north. 
In the foregoing I have made no reference to the direct, radiant 
heat from the sun ; nor has anything been said of the thermic 
influence on vegetable life. These subjects are of very great im- 
portance, but their discussion can perhaps be better undertaken 
at a future time. 
It should not be thought that in pursuing the present inquiry, 
I have ignored the other influences which climate exerts upon man ; 
acknowledging those only that manifest themselves by sensations 
of heat or cold. This is not the case ; but Ido maintain that such 
appear to our present view as by far the most important, as well 
as the most amenable to investigation. 
I earnestly desire the cooperation of others in developing the 
untrodden field which forms the subject of this paper. Everything 
in my power which can aid any one wishing to prosecute similar 
observations, shall be done with the utmost heartiness. Work of 
this sort is arduous and exacting, and until it is taken up by many 
persons, its progress will be slower than its importance demands. 
[Printed at the Salem Press, April, 1876.]