2.

REPORT OF LIEUTENANT CHARLES KELLER, CORPS OF ENGINEERS.

WILLETS POINT, NEW YORK, May 11, 1891. COLONEL: I have the honor to submit the following report on tests of Columbia powder. All charges used weighed 100 grains. In each case the service fuze was used to detonate the charge:

b Experiments made April 9, 1891.

c This observation rejected; guide rods were loose.

d Experiments of April 20, 1891, made for the purpose of determining the best form of cartridge paPortland cement used instead of Rosendale in this and succeeding experiments.

per.

From the above experiments it is seen that the cartridge paper paraffined gives results about one-eighth larger than the ordinary cartridge paper. All the cartridges used in the experiments of April 20, 1891, had been kept in store for about 1 month. Cartridges are now in store and will shortly be tried, which are made with ordinary-sized writing paper.

The Portland cement used in the later experiments appears to be preferable to Rosendale. The Portland cement being much finer, acts more in the manner of a gas check.

Respectfully submitted.

CHAS. KELLER, Lieutenant of Engineers.

Lieut. Col. W. R. KING,

Corps of Engineers.

APPENDIX E.-TESTS OF BUILDING MATERIALS.

REPORTS OF LIEUTENANT A. M. D'ARMIT, CORPS OF ENGINEERS.

1.

WILLETS POINT, NEW YORK HARBOR, July 29, 1890. COLONEL: I have the honor to submit herewith the results of the tests of sandstone sent from the Kanawha quarries by Colonel Craighill. In general the tests were conducted in the same manner as similar tests made last year. Experience seeming to indicate that pasteboard makes a better bearing surface than pine wood as used by General Gillmore, the former has been used exclusively, and the uniformity of the results and the nature of the fracture seem to justify the assumption that it is the best material yet tried. The specimens were all perfect 2-inch cubes from three different quarries; the specimens from McCoy's big and small bowlder quarries presenting little difference, however. Wishing to try something that has never before to my knowledge been done, I divided the specimens into two groups as nearly alike as possible. Those of Group I were tested in the usual manner and the results are given in the table. Group II was placed in water for 72 hours previous to crushing and then tested while in a saturated condition. The table shows the marked effect this has, the average loss of strength in both quarries being 16 per cent., so large a loss that it is well worth careful consideration where such sandstones are to be used in subaqueous structures. In the ninth column is given the ratio of absorption under 150 pounds pressure per square inch continued for 1 hour. Such absorption of water under pressure would no doubt still further reduce the strength of these sandstones, especially as it seems to have a deteriorating effect on the stone itself, rendering it extremely friable.

Very respectfully, your obedient servant,

Lieut. Col. W. R. KING,

Corps of Engineers.

A. M. D'ARMIT, Second Lieutenant of Engineers.

2.

WILLETS POINT, NEW YORK HARBOR, April 22, 1891.

COLONEL: I have the honor to submit herewith the results of tests ordered made on the Portland cement being used in the construction of the museum.

A mistake was made at first owing to the fact that two kinds of cement are being used and the workman obtained the wrong kind. This led to the decidedly unfavorable verbal report I made to you April 6, 1891, and an apology is due the company making the Portland cement for the report made to them on its condition. Incidentally, this mistake was valuable as showing that the Rosendale cement being used is destitute of hydraulic properties, although possessing considerable strength when dried and set in air. The tests of the Portland cement were made under the same conditions as the cement tests I made last year, a description of which is contained in my report of June 5, 1890.

The mean of 9 specimens made of one part cement and two parts sand gives 166.6 pounds breaking strength per square inch.*

Some briquettes of pure cement were tested and broke very uniformly at about 500 pounds, or a stress of 222.2 pounds per square inch of cross-section.

The behavior of the cement with sand is very creditable; but I am somewhat surprised to find that the pure cement does not give a higher tensile strength as compared to the sand briquettes.

Very respectfully, your obedient servant,

Lieut. Col. W. R. KING,

Corps of Engineers.

A. M. D'ARMIT, Second Lieutenant of Engineers.

3.

WILLETS POINT, NEW YORK HARBOR, June 22, 1891. COLONEL: I have the honor to report that in compliance with your verbal instructions I have made the additional tests requested by the Keystone Cement Company. The cement was taken from the box sent by them for this particular purpose. The briquettes were very carefully made and were exceptionally fine specimens. They were set 1 day in air and 7 [6] in water. On testing, however, they failed to justify the claims of the Keystone Company, the maximum strain borne by the neat briquettes being 525 pounds, or 2334 pounds per square inch, the average being about the same as found at the previous trial.†

4.

WILLETS POINT, NEW YORK HARBOR, July 15, 1891. COLONEL: I have the honor to submit herewith the result of the tests made of the Rosendale cement now being used in making the concrete for the parapet. The specimens were made as usual and under my personal supervision, so that there is no reason to suspect the workman of not making the briquettes properly. After 1 day in air the specimens were placed 6 days in water and then allowed 1 day to dry, so that the circumstances were most favorable. Notwithstanding this the sand briquettes (2 parts sand, 1 part cement) all broke with the slightest pull with the hands and could be crushed between the fingers. The pure cement did a little better. Four specimens gave 100, 120, 95, and 105 pounds, respectively, a mean of 105 pounds per briquette or 463 pounds per square inch. I think this result very unsatisfactory. Compared with the tests reported by me June 5, 1890, it will be seen that the sand briquettes were about the same quality, while the neat cement seems poorer. On the whole I should say the Rosendale cement possesses very slight hydraulic properties..

Very respectfully, your obedient servant,

Lient. Col. W. R. KING,

A. M. D'ARMIT, Second Lieutenant of Engineers.

Corps of Engineers.