REPORT OF BOARD OF CONSULTING ENGINEERS, PANAMA CANAL.


 Mr. STEVENS. I could not tell without more examinations. The only sand I know of is sand in the Chagres River, outside of the beach sand. That would have to be decided by investigation.
 Mr. GU] RARD. I have read in the French reports that when they required any small quantity of sand they have had to pay as much as $4 a cubic meter for it, and if a large quantity was required the price would be much more.
 Mr. STEVENS. Well that would depend upon the quality of the sand in the Chagres River. That could be obtained at a very much less cost if it is suitable. As far as the quantity is concerned, in most of these streams where there are quick sharp rises, gravel and sand are brought from the upper regions of the river and deposited in a bar, and if that bar is removed, after the next high water it is formed again, so your supply is perpetually renewed.
 Mr. QUELLENNEC. I think it is possible to have selected stone to make an artificial sand that is very good.
 Mr. RANDOLPH. Have you had any experience in crushing this rock for sand?
 Mr. STEVENS. I have had a good deal of experience in crushing trap rock for concrete. Are you familiar with the sandstone quarries of Minnesota? That is a most remarkable deposit of sandstone. The better class of it will average 98 per cent pure silica. I screened that very carefully and sifted it for concrete and heavy foundations, and I think it made the most perfect matrix I ever saw.
 Mr. RANDOLPH. Mr. Noble told me he expected to use the trap rock out of his excavations in the same way.
 Mr. BURR. I would like to say in regard to that matter of using artificial sand that I believe there are few good rocks that are not perfectly available for that purpose. I have had a pretty extensive experience during the last few years in connection with foundation works in Harlem and the large reservoir which is just now built in New York City. We used and have constantly been using the entire product of the crusher. That was contested very bitterly by certain political critics on part of the city work, but it was established beyond all question to be most excellent material, and I believe that any good rock can be used in precisely the same way; that is, every particle from the crusher can be used.
 Mr. STEVENS. I have read and have been told that some experiments have shown that a little admixture of clay in the matrix is a good thing.
 Mr. BURR. I only know the results of some experiments. I should not advocate the mixing of clay with sand, but it is a fact that there are a large number of tests at the present time that show that an admixture of a small quantity, I do not know what the limit is, appears to be to some extent advantageous.
 Mr. STEVENS. I have been in the habit of washing my rock very clean.
 Mr. BURR. I do not think there is any need of it.
 Mr. PARSONS. The Chinese have always put clay in their concrete, and judging from the flat arches of their bridges they ought to know something about it.
 The CHAIRMAN. If there are no more questions, the Board will excuse Mr. Stevens, thanking him very much for his assistance.


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