[Reprinted from the Journal of the Franklin Institute, July, 1865.] 
The FUTURE WATER SUPPLY of PHILADELPHIA.* 
By Col. William Ludlow, 7 
Chief Engineer of the Philadelphia Water Department. 
Vice-President Frederick Graff, introduced Col. Ludlow, who 
spoke as follows: 
Mr. President, Ladies and Gentlemen:-I must admit that I 
am somewhat taken by surprise when I received the invitation from 
the very excellent Secretary of the Institute, requesting me to attend 
the meeting to-night and make some remarks regarding the future 
supply of the city; I was under the impression that the meeting would 
resolve itself into an informal professional discussion of the matter, 
but I find that I am to have the field somewhat to myself and to talk 
to more people than I had anticipated. I know, however, that you 
are all interested in the subject as well as I, but I have not prepared 
any formal address and shall confine myself, therefore, to general 
remarks as to the present aspect of the important question of the 
future water supply of this city. 
The subject is not new. I think my friend, the President, will 
admit that it was an old one in his early days, and it has so continued 
to the present. Agitation of the subject has continued for a genera- 
tion past without definite conclusions being reached although we are 
approaching more and more closely to the necessity for reaching a 
decision. This futility of discussion has resulted mainly from the 
* Abstract of remarks presented at the Stated Meeting of the Franklin 
Institute, held Wednesday, April loth, 1885. 2 
absence of full and accurate investigation of the real facts upon which 
alone a reliable and final judgment can be made. The situation is 
about this: Philadelphia is a city happily situated in many respects, 
with a great river on either side; one stream, the Schuylkill, drains a 
mountain region and has been looked to both to supply the water 
needed for municipal purposes, and even to furnish the power by 
which that supply should be pumped and delivered to the citizens. 
Hence the construction of those early water works at Fairmount, 
originally breast wheels, which were later converted into turbines and 
which have continued in service to the present day. With the growth 
of the city came the necessity for an increase of quantity, and from 
time to time the appliances for augmenting the daily pumpage have 
been multiplied until now there arc no fewer than eleven engines at 
four great pumping stations drawing from the Schuylkill river into 
which, to a considerable extent, the waste matters of the valley are 
poured. On the other side of the city is a great tidal stream which 
receives the waste matters of the community, and at two points upon 
the Delaware we have been drawing these waters to supply the dis- 
tricts of Kensington and Frankford, but it has long been recognized that 
the water pumped at Kensington contained matters prejudicial to 
health, and the quantity of this was increasing year by year; this 
station has therefore been abandoned. The serious thought of those 
who from time to time have been charged with or interested in this 
vital matter of Water Supply have been turned to the consideration 
of the means of amending the defects of quality and quantity. There 
are two sources whence the city of Philadelphia can take its water, I 
mean practical sources as determined by engineering considerations; 
namely, the valley of the Schuylkill and the valley of the Delaware. 
The problem to be solved is whence a suitable supply both in quality 
and quantity can be derived to the best advantage; namely, at the 
lowest cost of construction and the lowest future cost of maintenance. 
A gravity supply is advantageous when practicable, for the reason that 
the water intercepted at a sufficient elevation will pass from its source 
to the city through the conduits, as water will flow down hill, whereas 
the raising of the large quantity of water required for the supply of 
the city involves heavy expenditure for machinery, and a constant 
annual charge for fuel and service. 
For two years past the Department with which I have the honor to 
be connected, has assiduously sought to gather all the information 3 
bearing upon this matter which was attainable by topographical and 
hydrographical surveys, by meteorological observations, by chemical 
analyses and by sanitary inspections, endeavoring to cover the entire 
field within which lay facts pertinent and important. Our observa- 
tions are drawing to a close. About nine-tenths of the field of explo- 
ration have been covered, and I trust that within another year we shall 
be enabled to complete and digest the information so gathered and 
present to the city, and to the engineering world the results of our 
labor in complete shape. It was for lack of this information that 
previous investigations have been rendered futile. The most important 
report which has been made upon this subject was presented about ten 
yeears ago, in 1875, when in anticipation of the celebration of the 
Centennial, a commission of eminent engineers was gathered to con- 
sider the entire subject, taking into account both the condition of the 
present supply and what should be done for the future. That their 
report, containing most valuable information, should have resulted in 
inaction is largely attributable to the fact that they were without the 
necessary exact data for final judgment. They made the best recom- 
mendations which, under the circumstances, could have been formu- 
lated, but in the light of fuller information it is neceasary to differ in 
some respects from the preliminary conclusion which they reached. 
At present I cannot say that I am prepared to announce final con- 
clusions as to the general solution, but it appears to lie in the choice of 
two projects. 
Many years ago Mr. Birkinbine, who was then the Chief Engineer 
of the Water Department, proposed to secure a suitable gravity supply 
by impounding the waters of the Perkiomen Creek, the most import- 
ant affluent of the Schuylkill river, which, from the supposed ample 
flow and purity of its drainage promised to be satisfactory and suffi- 
cient. The project contemplated the construction of a high dam near 
Schwencksville where the valley was narrowed and the rocky banks 
afforded a suitable site for a construction of this kind, and the Com- 
mission of 1875 were inclined, upon the data at their disposal, to favor 
this project, especially as the estimates of cost of a supply from the 
Delaware were vastly greater. Were we sure of ample amount and 
good quality, the Perkiomen project would present undoubted advan- 
tages of a high order. Unfortunately our investigations tend to show 
that the flow of the stream, even aided by gathering the waters of 
some of its affluents, is insufficient for the total quantity that Phila- 4 
delphia will require in the near future. The Delaware project had 
never been carefully investigated, and for this reason: in 1883 two 
parties were formed, one to run a conduit line to the Perkiomen and 
elaborate the necessary information ; the second party to run a corre- 
sponding line northward to the Delaware with the view of extending 
the investigation to near the Water Gap, at some elevation which should 
be found sufficient to permit the river to flow into the conduit and 
thence into the city, and the apparent probability of the insufficiency 
of the Perkiomen gave greater weight to the Delaware project than it 
had hitherto borne. 
In considering the route toward the Gap, an examination of the map 
showed that an elevated region, designated as the South Mountain, 
stretching from northcast to southwest, lay across the Peninsula 
between the two rivers and would bar the construction of an aqueduct 
without extensive tunneling. A line northward from the city to the 
Delaware river reaches that stream at a point just below the gorge or 
the South Mountain, and a practicable conduit line upward could 
thence be made by following the valley of the stream, and thus evade 
the formidable obstruction which the mountain presents. Pursuing 
this plan, the surveyors were pleased to find, in the first place, an 
unexpectedly favorable line to the Delaware at Point Pleasant, half- 
way between Trenton and Easton, and the analysis of the water of the 
Delaware at this point further proved that in quality it was little infe- 
rior to the noted waters of the Gap itself. 
This was our discovery. Furthermore, in proceeding northward 
from Philadelphia the conduit line crosses the valleys of several creeks 
of considerable volume-the Perkiomen, the two Neshaminies and the 
Tohickon-the latter stream discharging- into the Delaware at Point 
Pleasant. The thought at once suggested itself that by utilizing the 
flow of these streams they could be intercepted, turned into the conduit 
and sent to the city by gravity, and that for a greater portion of the 
year the flow of these would be sufficient to supply all requirements, 
and that for such time as this flow should be deficient it could be made 
up by pumping from the Delaware itself. This, practically, consti- 
tutes a new project as compared with that of drawing water from the 
Gap entirely by gravity, and the expense of this construction was 
moderate enough to bear comparison with the Perkiomen project. It 
was found, for example, that the distance, in each case, was about the 
same, namely, thirty miles, and that the cost of construction was also 5 
about the same, namely from $6,500,000 to $7,000,000. This esti- 
mate, you will understand, is that of the cost of the construction of the 
conduit merely, without adding other items (which will no doubt be 
large), for dams, land damages and other contingent expenses. 
These conduits, I might say, arc designed to be twelve feet in dia- 
meter with a grade of one foot in six thousand and with a capacity of 
delivering to the city 210,000,000 gallons a day at an elevation of 166 
feet above city datum. This elevation is that of the existing Wentz 
Farm Reservoir,on the county line northwest from Bridesburg, and of 
the proposed Cambria Reservoir in the upper portion of the Twenty- 
eighth Ward. 
With regard to this question of quantity, the following considera- 
tions present themselves : Our present pumpage is about 70,000,000 
gallons a day, with a population approximating closely to a million 
people. A generation hence Philadelphia will contain two millions of 
inhabitants. The supply must therefore be doubled which would make 
it about 150,000,000 gallons a day. Furthermore, allowance must be 
made for the fact that in a large community like ours the use of water 
for the multiplied purposes of manufacturing and domestic uses increases 
in a greater ratio than the population itself. With works of the 
magnitude and cost of these which we have been discussing, it would 
be folly to project for a smaller supply than will be required within a 
generation, and for this reason 200,000,000 or 210,000,000 gallons 
were estimated for and the dimensions and grade of the conduit were 
thence determined. 
Going back now to the question of distance and cost it will be seen 
that exact observation proves that for the first time the two projects, 
the Perkiomen and the Delaware, began to balance each other, and 
should the Perkiomen prove insufficient the Delaware project would 
practically stand alone; but in order that all possible ground should 
be explored I directed the examination of the upper Lehigh, a stream 
with which I was personally familiar from frequent journeys over the 
mountains to the Susquehanna Valley, and which, although so distant, 
possessed favorable characteristics from the purity of its water and the 
great elevation of its water shed. When, therefore, the Perkiomen 
proved of doubtful adequacy, the acute suggestion was made by Mr. 
Hering, who in a most thorough and capable manner has had immediate 
charge of these serveys, that were a sufficient amount of the waters of 6 
the upper Lehigh brought into the upper valley of the Perkiomeh a 
most excellent supply could thereby be secured. 
You will observe that in all this matter the question of quantity has 
been of vital importance. We want 210,000,000 gallons a day. Now 
the low-water flow of the Delaware at the Water Gap in 1883 at a 
time when the stream was lower than it had been within the memory 
of the oldest inhabitant, was gauged and its flow at that time found to 
be about 700,000,000 gallons of most excellent quality. At Point 
Pleasant the volume of the river is about one-third greater than this, 
and in quality nearly as good as at the Gap. The Lehigh has a mode- 
rate flow. Its minimum in 1883 being about 70,000,000 gallons, but 
with excellent facilities for storing water at a great elevation above the 
reach of pollution. The bringing of this down into the upper valley 
of the Perkiomen would double its supply and the combination would 
once more have the prestige of a practicable and promising project. 
At present, therefore, these two projects lie before us for considera- 
tion and ultimate decision, and, as I said before, within another year I 
trust that the problem will have been solved. 
It may be of interest to explain how it happens that with the Schuyl- 
kill flowing past our doors all the engineers who have studied this sub- 
ject seem to have concluded that at some time or other the Schuylkill 
River itself must be abandoned as a source of water supply. The rea- 
sons are these : The origin of the Schuylkill is in the mountains among 
the coal mines. The drainage from the coal measures, supplemented 
by the large amount of pumping from these mines constitutes a volume 
of acid water which fills the upper portions of the stream and is unfit 
either for drinking or manufacturing purposes, or even to sustain life. 
No fish can exist in it, nor can human beings drink it. In the course 
of its flow downward the Schuylkill above Reading traverses a geological 
belt of limestone whence considerable affluents feed the river, bringing 
with them a solution of the lime and the alkaline waters mingling with 
the acid waters of the parent stream neutralize each other and become 
again fit for ordinary purposes and for the existence of fish. There- 
after we have no further difficulty in this respect; that is with regard 
to the chemical characteristics of the water. The water as it reaches 
Fairmount Dam is sometimes slightly acid, sometimes slightly alkiline 
and sometimes neutral. But the important fact remains to be noted 
that the valley through its length is a populated district from end to 
end, and into it are poured all the waste matters of a large and busy 7 
population ; every town and industry contributing its quota of pollu- 
tion, whether sewage or the waste products of manufacturing establish- 
ments. With two great railroads extending up its banks and with 
communities and towns increasing year by year in number and popula- 
tion, the Schuylkill can be described only as an industrial valley which 
in the future will be densely populated, and it becomes manifest at 
once that unless extensive engineering constructions be planned, 
strict legislative enactments be passed and rigid enforcement of these 
laws be insured, the waters of the Schuylkill must continue to receive 
deleterious matters in constantly increasing quantities, and that ulti- 
mately they will cease to be available for the purposes of that great 
city which lies at its mouth and absorbs the contaminations of every- 
thing above. 
The population of the valley above Philadelphia, at present, is in 
excess of 350,000, and if we are to endeavor to protect the stream from 
this pollution, which is not only nauseous in contemplation, but in fact 
dangerous to health, sewers must be built upon both banks which shall 
intercept and discharge all waste matters and convey them down the 
entire length of the valley until they can be discharged into the Dela- 
ware River below the city. 
Another important fact must be observed; within sixty years a 
marked diminution has taken place in the minimum How of the stream. 
Sixty years ago the summer How of the Schuylkill was estimated at 
500,000,000 gallons a day. Successive estimations of the low-water 
flow were made from time to time, all showing a diminution in quantity 
until that in 1874 determined the minimum flow as 250,000,000 gallons. 
Here, then, within this period the low-water flow of the stream had 
decreased one-half, and, supposing that it had gone no further than 
was observed at the last examination, the flow of the stream when at 
its low stage is little more than the city will require a generation hence. 
It follows that with but a slight shrinkage comparatively, in the future 
the city would be pumping up the entire river. I do not wish to be 
misunderstood with regard to this, and therefore beg to explain what 
I mean by the minimum flow : It is not probable that the total annual 
flow of the Schuylkill has decreased. This flow is dependent upon the 
rainfall, and cannot in the absence of any marked changes in the rain- 
fall be itself materially modified, but the destruction of the forests in 
its head-waters, the clearing and cultivation of lands, have to a great 
extent deprived the river of that power of conservation which belongs 8 
to wood land, whereby the rainfall is held back and checked, as it were, 
in its passage to the stream, and the flow is more nearly equalized 
and prevented from dashing down and passing out. With the removal 
of the forests this fact ensues: The rainfall rapidly descends to the 
stream, creating a freshet which sweeps down the valley and passes out 
and is lost. During periods of drought, the rains being suspended the 
river shrinks, its flow becomes moderate and its movement gentle, and 
presently we attain the minimum discharge. 
In depending upon a stream, without taking means to restrain the 
passage of freshets, it is manifest that we can pump no more from the 
river than it will daily bring to us, and the minimum flow therefore 
should be as carefully investigated as we would investigate the strength 
of the weakest link in a chain from which we intend to support a 
weight. 
It would be possible by means of dams across the stream to impound 
some portion of the volume of these successive freshets until the periods 
of drought, which occur always in summer and frequently in winter, 
and to draw upon these reservoirs when required. But again that 
question of the pollution of the stream comes in, occasioning doubt as 
to whether should this be done, it might not be found in the end that 
large expenditures had been wasted by reason of the inferior quality of 
the water and the injudiciousness, of depending in perpetuity 
upon it. For the reasons given the water varies greatly from time to 
time in its chemical character, potability and wholesomeness. At times 
during the passage, for example, of the freshets the waters of the stream 
being largely the results of recent rainfall, are in good condition; at 
other times they are highly charged with pollution and occasionally 
get themselves into a condition of the most nauseous offensiveness. It 
is manifest that unless these difficulties can be amended the Schuylkill 
cannot continue to be regarded as a suitable supply for a population 
like this, and the vital importance to modern communities of a bountiful 
supply of wholesome water for all purposes is so great as to constitute 
one of the most serious problems relating to municipal existence, and 
sooner or later there is not a city in the world that has not this important 
matter to decide. 
I have endeavored to present to you briefly the aspects of the pro- 
blem precisely as they present themselves to-day. It is one in which 
every individual is in the highest degree interested. It is one upon 
which the future prosperity and welfare of this city depend. 9 
I am very much obliged to you for your attention, and trust that 
some one will take up the discussion at this point. 
DISCUSSION. 
Prof. Houston.-The exceedingly interesting remarks the gentle- 
man has just made are enough to give thoughtful people con- 
siderable matter for reflection. The question of the water supply of 
any great city must always be a difficult one to solve, since as the needs 
for an increased amount of water grow, the ability of the ordinary 
means to give a large supply of pure water decrease. The rivers of 
any country are the natural sewers into which the dirt and filth of 
that country drain ; and to safely take the water supply of a large city 
from any river requires considerable thought and skill. 
The problem as to the water supply of the city of Philadelphia is 
one to which we have all given considerable attention. A number of 
years ago, I called the attention of the Franklin Institute to what I 
regarded as a dangerous pollution of the Schuylkill River; and I 
am glad to hear Col. Ludlow speak in such plain and unmistakable 
language concerning the probabilities of the near future of the Schuyl- 
kill. I take it that the real danger coming from drinking Schuylkill 
water does not exist with equal gravity all the year. During a large 
part of the year the lower basin of the Schuylkill, from which most 
of our city's supply is taken, is practically in the condition of a 
" steppe-lake," that is a river without an outlet. 
Under these conditions, its impurity increases from the loss of pure 
water by evaporation. For many months in the year, the citizens of 
Philadelphia know that comparatively little or no water goes over the 
dam, and were it not for the water which goes through the locks, 
there would be no discharge at all except that which is pumped into 
our reservoirs. Under these conditions, we are actually damming up 
the river and drinking its contents. During many months in 
the year, and particularly those months when we should be the most 
careful of the purity of our drinking water, we are drinking some- 
thing that is far from wholesome. I have not the slightest hesitation 
in expressing this as my opinion. During this time of the year, from 
a water itself impure, we pass off a large quantity of pure water by 
evaporation, and drink the dregs. Now we do not want the dregs of 
the Schuylkill, especially when in the immediate neighborhood of our 
pumping stations we have the outlets of sewers. 10 
Of course, Schuylkill water cannot be as poisonous as many allege, 
else we would not be here. The main point, in my mind, is: Can 
we rely on the Schuylkill for our water supply in the near future, say 
for the next fifteen or twenty years ? Col. Ludlow has stated the 
problem very clearly. The very conditions of the valley of the Schuyl- 
kill seems to render it improbable that we can continue using the water 
for drinking purposes. 
The destruction of the forests over the upper basin of the Schuyl- 
kill, unquestionably favors the rapid drainage of the rain water; 
so that, for a considerable part of the year, we have so limited a sup- 
ply that, as has already been shown, we endeavor to drink the entire 
river. Unfortunately, too, during that time in the year when the 
rain water would make the river comparatively wholesome, by diluting 
it with pure water, the rapid drainage brings down the filth and sew- 
age accumulations from the river banks. So the very time we ought 
to get comparatively pure water, we get it very impure. You are prob- 
ably aware of the fact that when the water looks the dirtiest, it is not 
necessarily at its worst. In this condition it is often less harmful then 
than when quite clear. 
I therefore thoroughly agree with the speaker that the Schuylkill 
cannot be relied on for our future water supply; nor to my mind can 
any simply impounded basin be relied on for the water supply of 
Philadelphia. We have in any impounded basin the very conditions 
going on to which I have alluded in speaking of the lower Schuylkill. 
If you dam up a stream and let even pure water run into it, there 
will be discharged into the air, as vapor, pure water and comparatively 
impure water will be left in the reservoir. I believe it has been the experi- 
ence of almost all our large cities that have tried the impounding plan 
that it does not give satisfaction; not only from the disagreeable 
cucumber odor given to the water, but from other reasons. 
The Schuylkill must undoubtedly for many years to come be looked 
upon as the source of our city's water supply; but, looking beyond 
this time, can we safely, for the next three or four generations, 
derive our water from this river? Were this river all we could get, 
of course we must go to it. That settles the question. I do not, 
however, believe so. It has sometimes seemed to me not such a very 
wild or visionary scheme to go to some magnificent natural subsidence 
reservoir like any of our great lakes. I know the distance is very 
great, but so is the population along the Atlantic seaboard. If some 11 
plan could be devised by which our large cities could share the expense, 
then it does not seem to me so impracticable to look to the great lakes 
for our water supply. 
We have other waters than the Schuylkill, however, close at hand. 
It is indeed a very fortunate circumstance if, as Col. Ludlow has 
remarked, the upper sources of the Delaware will probably, from their 
character, never for a loug time to come be improved or cultivated. If 
no mineral deposits that would lead to extensive mining operations 
be discovered in the upper basin of the Delaware, then we may per- 
haps rely on the Delaware for our future water supply. But even here 
does not the same old question still suggest itself? Will not, in the 
remote future, the valley of the Delaware become densely populated 
and thus pollute this stream? 
There is one thing which to my mind seems somewhat of a danger, 
and that is the discharge of the Intercepting Sewer into the Schuylkill 
immediately below the dam. There is scarcely opportunity for 
the suspended solids to do anything but settle immediately in the bed 
of the river. I am aware that the discharge of the sewer at this 
point is but a temporary expedient; but I fear we are going to per- 
mit a temporary expedient to bring a great deal of trouble on Phila- 
delphia; a trouble that may cost much to remove. 
Already some of the best sections of our city discharge their sewage 
into the river below the height of mean tide. On the rising of the 
tides the water backs up the sewer and causes a dangerous leakage of 
sewer gas into the houses; added to this, the prevalent southwest wind 
brings very unpleasant odors as it is from the lower Schuylkill; so that if 
we add to these sources of danger, that arising from the formation of sew- 
age deposits in the Schuylkill at this point, the danger may become 
very grave. It does seem to me that this is something that we ought 
to be very careful about-spend a little more money if necessary-and 
carry the discharge a little farther below the mouth of the dam. 
We have only to look at the forebay of the Fairmount Water Works 
to see the possibility of sediment collecting to the depth of several feet, 
right alongside of the inlets to the water wheels. Here, despite the 
velocity caused by a fall of many feet to the wheels, some six or 
eight feet of sediment had collected. I think there is a very great 
danger from similar deposits of sewage from the Intercepting Sewer, 
and one that ought to be attended to. 12 
Mr. Graff.-I hoped to have this matter thoroughly discussed 
among the audience present to-night. Many of them have studied it 
to some extent and have come to it with new light. We may some- 
times look so long at an object (which is really true of painters and 
artists) that we lose its true proportions and have to leave it and come 
back to it again before we are able to see its full merit. I may proba- 
bly be in that position; therefore, I feel that there may be parties here 
who might look on and diseusss this matter with new light. I think 
there may be one thing said, and that is the point to which Col. Ludlow 
has referred : the fact that until the period when he was enabled by 
action of Councils to take up the matter there had never been suitable 
surveys made such as would enable the citizens of Philadelphia or the 
engineers employed to come to any positive conclusion in regard to the 
proper future supply of the city of Philadelphia. I am glad to say 
that these surveys have now been carried on for some length of time; 
not only have been carried on, but with the utmost care and with all 
the light and science that can be brought to the subject. Probably 
many of you realize how much there is to be considered. The devel- 
opments of the day have taught us all very much more than we knew 
in former years; and the questions that attach themselves to this sub- 
ject are so numerous and varied that it would be tiring you to go into 
them to-night. There are not only the surveys of the country; there 
are other objects besides that. We are only learning now how much 
of the rainfall can be utilized from a given area of county and how 
pure it will come to us when we get it. That matter is made variable 
by the condition of the country, particularly the wooded condition, the 
effect of cutting off the timber of the forests and all such matters. Col. 
Ludlow has shown you by demonstration that the Schuylkill river is 
now suffering from reduced volume produced by that cause. There- 
fore it behooves us all, and particularly those interested in the subject, 
to study thoroughly what may be the effect upon the Delaware and 
other streams suggested. Continued studies of these points have to be 
made when considering such a subject as this. They are now being 
considered. The geology and the surveys of the county examined 
have been so thoroughly gone over by Col. Ludlow that they are 
resorted to, and as far as they go, will be used for the geological surveys 
of the State; this is to show how thoroughly the surveys are being 
made. I agree with Col. Ludlow, that at this stage of the matter, it 13 
would not be proper for any engineer to say positively what shall be 
the supply of the city in the future. 
It is only feeling our way just yet That way has been felt very far, 
and probably very soon an opinion, perhaps a very accurate one, can 
be formed. I shall be willing to leave the matter in the hands of the 
Chief Engineer until these surveyshave been completed and the whole 
subject thoroughly studied up. The balances that he tells you about of 
all the different plans investigated can then be made very important, 
but can hardly be gotten at until the surveys are completed. In the 
meanwhile, do what we may, we have to resort to the Schuylkill for 
our supply, because any comprehensive plan of supply is a work which 
will occupy much time. Even if we were to-day prepared to say that 
the Delaware is the proper source of future supply and the building 
of an aqueduct were determined upon to-morrow, the difficulty of get- 
ting from the State appropriations necessary to carry on such a work 
is so great that a number of years would elapse before it could be 
brought into use. Therefore, in the interim, we are obliged to do the 
very best that we can with the supply we get now. Prof. Houston 
has said, very properly indeed, that the Schuylkill has the disadvantage 
of being bottled up in Fairmount pool in the summer months, when 
the water is low and the outlets are only through the wheels at Fair- 
mount and the locks, because at that time the pumping there has to 
stop and steam power take its place. Therefore the ability of the 
stream to purge itself from impurities is reduced just at the time 
when you want it to be the most pure. Another point comes in with 
that consideration, and that is, to-day we cannot store sufficient water 
in our reservoirs to give it the possibility of subsiding in any way. I 
think F am right in saying that the maximum storage in summer in 
the reservoirs is scarcely two days of the whole supply. Therefore, 
any discontinuance of pumping, you will necessarily see must reduce 
the reservoirs to so low a point as to make it very unsafe. The reser- 
voirs are so small that the water may be said to simply go through 
them-in one side and out the other. No time can possibly be allowed 
for subsidence, whilst the storage capacity is so limited. As we have to 
continue using the Schuylkill the palliation, not an entire remedy, 
is the erection of larger reservoirs, a relief which I hope soon will have 
some attention. The subject of making an appropriation is now before 
the Legislature and possibly something will be done with it. The 
subject of the purity of the water in the Schuylkill (the impurity, I 14 
should say), is one there can be no kind of doubt about. At times it 
is measurably pure, at others it is not so. There is no use of disguising 
the fact. As I said before, a little palliation might be made by ability 
to store water. The subject of any relief of the Schuylkill, I think, 
has been pretty wrell gone over by the Chief Engineer. It is a very 
serious point; when you come in any way to disturb the industries 
upon the Schuylkill valley, of course there will be more or less diffi- 
culties; such difficulties the Colonel has encountered, and has to a 
certain extent met. Protection may be insured by the sewer now 
building to carry the impurities below the point of supply. After all 
the matter comes down to obtaining the light necessary to form an 
early decision as to what shall be the future supply. I think the sur- 
veys now making will give us this light, and with the head we have 
conducting them, we are likely soon to come to a conclusion on that 
important point.