gulch is how wide at sea level? I do not know how to compute it on this map.

General HAINS. Pretty nearly 2,000 feet. A little less than 2,000 feet across.

Senator MORGAN. That gulch is pretty nearly 2,000 feet across? General HAINS. At the top; yes.

Senator MORGAN. That has also been washed out of the indurated clay?

General HAINS. Well, perhaps.

Senator MORGAN. It is there?

General HAINS. It is there.

Senator MORGAN. Have you any better way to account for it than that it has been washed out?

General HAINS. I have no better way to account for it, but I do not know whether that was the way it was formed or not.

Senator MORGAN. We do not any of us know, but we have to take the probabilities and compare them and arrive at what we conceive to be, at least, a fair conclusion. All of that gulch is filled up with permeable material, is it not?

General HAINS. No, sir; I think that material is mostly impermeable. Senator MORGAN. Down in that gulch?

General HAINS. Yes, sir.

Senator MORGAN. Where is the permeable part of it, on top-at the upper part?

General HAINS. Down at the bottom. The most permeable part is down at the bottom.

Senator MORGAN. The report of the borings there is that at the depth of 50 feet below sea level, I believe it is

General HAINS. About that.

Senator MORGAN (continuing). The wells that were driven down for the purpose of ascertaining whether the water was in here and in here [indicating on blueprint] brought up water at a uniform level, or about a uniform level, in each of these gulches. The engineers who testified here, I believe all of them, come to the conclusion that the water that was thus forced up through those pipes belonged to a common body, and that what went up through the pipes in this deep gulch was the same body of water that went up through the pipes in the shallower gulch, and that therefore there was some substructure or substratum that was permeable, and there was communication on each side of this island. Do you concur in that?

General HAINS. That there was communication?
Senator MORGAN. Yes; between the waters.

General HAINS. No, sir; I do not.

Senator MORGAN. You do not?

General HAINS. No, sir.

Senator MORGAN. They spoke very decidedly about that, particularly Mr. Wallace. There is permeable material, though, lying at the bottom of this broad gulch that I have just described, and also this narrower one which runs down to 258 feet below sea level?

General HAINS. Yes, sir.

Senator MORGAN. The permeable material is in the bottom of these gulches?

General HAINS. Yes, sir.

Senator MORGAN. Do you consider that there is no necessity for stopping off the flow of water in the permeable material or otherwise obviating it or obstructing it in order to get a firm, permanent basis for the dam that reaches across both these gulches?

General HAINS. I do not think there is any necessity for stopping that seepage. At the same time I believe that seepage can be stopped, and at no great expense, either.

Senator MORGAN. How would you proceed to do it?

General HAINS. There are two methods that I have in mind which are practicable, in my opinion. One is to force cement grout down into that permeable material that is, it is coarse sand, which will fill up the interstices and solidify the whole of it, making it practically rock. I do not regard that as at all an impracticable undertaking. Senator MORGAN. Let me ask you right there whether you know of any great dam that has ever been filled upon such a foundation? General HAINS. Such a foundation as that?

Senator MORGAN. Yes; a cement foundation pumped into the bottom of it.

General HAINS. No; I do not recall any where any seepage has been stopped by this process-that is, for any great depths. The Assiut dam, on the Nile, is built entirely on sand, and for a great depth under it-I do not know how many feet-but for a great depth under it there is nothing but sand, all of which is water-bearing, with a pressure of water in the river above the dam considerably above that below it.

Senator MORGAN. Are you speaking of the dam that spans the Nile, or the dam that flanks it?

General HAINS. It spans the Nile at the place called Assiut. I am not speaking of the Assuan dam. The Assuan dam is built on rock. Senator MORGAN. Yes.

General HAINS. I mean one up near Cairo. This dam has had grout forced under it to so solidify the material to a depth of something like 30 feet, I think.

Senator MORGAN. Thirty feet?

General HAINS. Yes, sir.

Senator HOPKINS. And below that is the sand, through which the water seeps or can seep?

General HAINS. Yes; it is supposed to seep through there, but it has not affected the stability of the dam.

Senator MORGAN. Is that an earth dam or a sand dam, filled up on top of that?

General HAINS. That is a masonry dam.

Senator MORGAN. A masonry dam built on the top of this-
General HAINS. On this sand foundation.

Senator MORGAN. Filled with grouting?

General HAINS. The under part; yes, sir. The underlying sand is

filled with this grouting.

Senator MORGAN. Like a rock core underlying it?

General HAINS. Yes, sir.

Senator DRYDEN. How long has that dam stood there?

General HAINS. I do not know when that dam was built, but I think

it was built more than ten years ago.

Senator HOPKINS. What is the head of water?

General HAINS. That I can not say.

Senator MORGAN. About 25 feet, is it not?

General HAINS. I would not like to say, Senator. It is a matter that can be determined accurately. I do not carry these figures in my head any more than I can help, because I find that if I try to do it I am very apt to make mistakes.

Senator MORGAN. You have described one process by which you would undertake to intercept the water down there at the base of these two gulches. Is there any other process that you would rely upon? General HAINS. Yes, sir; there is another process that I think could be applied there. That is, by using steel sheet piling. If you will let that stand over for a few minutes, Senator, I have sent down for a specimen of this sheet piling, from which, when it is sent up here, I can show you how I would put it down, if you do not already understand it.

Senator MORGAN. I do not understand about the sheet piling. I never saw any of it, but I have heard it described a time or two-not described really, but referred to.

Would you feel safe in putting in such a dam as is to be superimposed above these two gulches without any protection against the percolation of water at the foundation among this coarse material? General HAINS. I should feel perfectly safe without it, yes.

Senator MORGAN. Have you any example of engineering in your mind that would give you a precedent that would contribute to your feeling of satisfaction and safety?

General HAINS. I do not recall just now large dams built on that kind of a foundation, but my understanding is that there are a number of them.

Senator MORGAN. Small dams, but not reaching down to two or three hundred feet, are there?

General HAINS. I say I do not recall any that are anything like these dimensions.

Senator MORGAN. It is the head of water that impinges against the dam, or presses upon the dam, that causes the danger of the washouts, is it not?

General HAINS. Yes, sir; and if it is not intercepted in some way or other there would be a head of water of 85 feet on the up-stream side of the dam, and if there was a streak of permeable material running from, say, what is now the bottom of the Chagres River, down that way and running out [indicating on map], some water would seep through; but I have no idea that the amount of seepage would endanger the dam. It might cause a loss of water, and if it was a case of water supply to a city it would be necessary to cut it off, because it might be of some importance; but in a case like this, where the number of feet are calculated to be so small, I can not see that there would be any danger from it. The mere seepage of the water through this stuff underneath does not, in my opinion, render the dam unsafe at all. If it could go through there with a velocity so as to move the particles along with it, that would be an entirely different thing; but it can not do that.

Senator MORGAN. When we find four or five engineers and they divide about equally, and one expresses the opinion that that is an element of danger, and the other expresses an opinion that it is not an element of danger, what are the laity to do?

General HAINS. Senator, you are in the same fix about the two types of canal.

Senator MORGAN. It looks to me as if we had better get a chuckluck box and throw high die for a judgment about it. [Laughter.] But they are all opinions. It is your opinion that this dam can be built upon this structure without anything being put down into this soft material, this coarse material.

General HAINS. Yes, sir; that is my opinion.

Senator MORGAN. That is your opinion. If it is the opinion of another engineer, say with equal experience and ability, that it can not be done with safety, would it not be better, General, in that case, to discard both of them and take a plan that does not require any dam? General HAINS. Why, no; I think the best thing under those circumstances is to accept what they say about its being dangerous and cut it off, which I say you can do by grouting it or by this steel sheet piling.

Senator TALIAFERRO. How much will that increase the cost?

General HAINS. Oh, I should not think it would add a half a million dollars to it.

Senator MORGAN. Well, that is not much in these times, you know, except to the taxpayers. They feel it sometimes, a little bit.

General HAINS. Speaking about this sheet piling, Senator, here is a specimen of it. That can be driven down. There is another piece over it, like that [ indicating], and that goes on here, with this part right in there [indicating], and that is used for cofferdam purposes now. It has been used to great depths, and after it is down it is absolutely tight. You can pump water out of that with perfect impunity.

Senator MORGAN. Would that sheet piling be put down in sections like this?

General HAINS. Not in sections like this. This is just a short section. It would be long, you know. It would be long enough to reach down to the bottom of the gulch here.

Senator MORGAN. To be secure, I suppose it would have to reach from the bottom of the gulch up to the

General HAINS. Clear up to the water surface, if you wish.

Senator MORGAN. Up to sea level?

General HAINS. Yes, sir; or even above it, if you want it to.

Senator MORGAN. It would not be put down as one solid mass of sheet piling, but it would be put down in sections, one resting upon the other?

General HAINS. One after the other.

Senator MORGAN. Driven down upon the top of each other?

General HAINS. Not on top of each other. You start with one up here, where you do not go down very deep. That gives you the bearing for the next one. [Indicating on blueprint. Then you come with the next one, and that goes down still deeper. Then you come with the next one, and that goes down still deeper, and then the next one, that goes away down here [indicating on blueprint] into this what you call indurated clay, which I think is a misnomer; then this one, and then this one, and so on, until you get across the valley. Then across the whole of this, if there is any seepage through it, it will be stopped, admitting that there is seepage. I do not think there is any except down at the bottom; but by this means you will cut it

off.

In the same way you will cut it off on this one [indicating on profile].

Senator MORGAN. If you use that sheet piling, or if you use the cement grouting, we will call it concrete

General HAINS. Not concrete, Senator.

Senator MORGAN. Well, grouting.

General HAINS. It is just cement and water mixed together.
Senator MORGAN. That is all?

General HAINS. Yes, sir.

Senator MORGAN. If you use either, how are you going to fasten that to the walls of this indurated clay, as you go down, so as to prevent a crack? You fill up across this gulch a broad sheet, in order to cut off the water; how are you going to fasten the bearings or the edges of this, either the sheet piling or the cement, to the wall of this indurated clay, so as to prevent a crack there?

General HAINS. The sheet piling I would drive into this indurated clay, driving it in a short distance. That will answer that question, I believe.

Senator MORGAN. Laterally in the side walls as you go down?

General HAINS. You see this is exaggerated [referring to blueprint profile]. This distance across here is about 3,000 feet, and this distance from here to here is only 200; so that you see that this sugarloaf line, you may say, does not convey the correct idea.

Senator MORGAN. Yes.

General HAINS. If this vertical scale was the same as the horizontal one, the bottom of that gulch instead of being away down there would be about there [indicating on blueprint profile].

Senator MORGAN. Yes.

General HAINS. You see, this is exaggerated. The scale is exaggerated in the vertical direction. If that were drawn according to the regular scale, it would come down along here [indicating]. That is the way that would be.

Senator MORGAN. But still it would come down in the form of an inverted cone?

General HAINS. Yes, sir.

Senator MORGAN. A sharp inverted cone?

General HAINS. Yes, sir; but instead of looking like a cone, it would be just a slight depression, like that; and that is all it is, in the rock. Senator HOPKINS. This does not fairly represent it, then [referring to blueprint profile]?

General HAINS. No, sir; that is exaggerated.

Senator MORGAN. That is exaggerated, but the figures are all there. General HAINS. The figures are all there, but it is exaggerated in order to put in these notes about what was found at different depths. That is a common practice. We always use those in drawings.

Senator MORGAN. This island of indurated material here, too, is exaggerated in the same way?

General HAINS. Yes, sir.

Senator MORGAN. So that, relatively, they are right, but nevertheless, in this direction—that is, toward the bottom of the blueprint-the appearances are calculated to deceive the eye.

General HAINS. That would be right down like that, if it was on the same scale [indicating].