Revised Statutes) requiring the procurement of supplies by contract after advertisement be so modified as to enable this Department to procure materials for tests in open market. The reasons for this are briefly given in this report. Under this section purchases in open market can only be made when the public exigency requires the immediate delivery. The "public exigency" is therefore one of time only, and it has been so construed by the Attorney-General. I respectfully recom mend that section 3709 be so modified as to exempt the procurement of material for tests from the operation of its requirements.

It is urgently recommended that Congress be asked to authorize frequent publications of the results of tests-monthly if possible-that information of such great value may be quickly disseminated. The present report of date August 31, 1882, will hardly issue from the Public Printer before next spring, at the very earliest-many months subsequent to the time when the results were obtained and ready for use.

I have also to recommend that Congress be asked to have printed five hundred additional copies of this report for the use of this office. The calls for it are many and constant, and this Bureau should be in condition to supply a limited number to those most interested. Very respectfully, your obedient servant,

The Hon. SECRETARY OF WAR.

S. V. BENÉT,

Brig. Gen., Chief of Ordnance.

REPORT

OF

TESTS OF METALS FOR INDUSTRIAL AND OTHER PURPOSES.

WATERTOWN ARSENAL, August 31, 1882.

SIR: I have the honor to report that during the fiscal year ended June 30, 1882, the testing machine at this arsenal has been kept busily at work in making tests for private parties and for industrial purposes agreeably to the provisions of the acts of Congress governing its use.

There have been tested during the year 1,587 specimens in all, of which number 855 were for private parties, and 664 were on Government account; the former occupied 97 days, and the latter 208 days. The private parties having work done were 33 in number, 2 of which were from Maine, 17 from Massachusetts, 3 from Rhode Island, 3 from New York, 2 from New Jersey, 4 from Pennsylvania, 1 from Michigan, and 1 from Kansas.

The specimens tested for private parties were by no means so large, the most of them, that they could not be tested on private machines of smaller capacity; many specimens were of quite moderate size, but the parties having tests to make seem to prefer to have the work done on the Government machine, having great confidence in the accuracy of its determinations and the care and faithfulness with which the work is performed.

Since the 9th of March, 1882, the date of your order directing that all money received for making private tests be covered into the Treasury instead of being used to pay the expenses of making such tests, as had formerly been done, there has been turned into the Treasury on this account the sum of $972.84. In addition to this the sum of $2,628.78 was turned into the Treasury from the appropriations of 1881 for making tests for industrial purposes, this being the amount of contracts entered into for materials which were not delivered according to agreement, within the stipulated time; and of the money appropriated for the last fiscal year the sum of $606.76 was covered into the Treasury on account of similar failures of parties to comply with the terms of their contracts. Thus of the moneys appropriated for making tests for industrial purposes $4,208.38 have not been used, but have been returned to the Treasury, mainly because of the want of promptness of contracting parties in furnishing materials for specimens to be tested agreeably to the terms of their contracts. This strict adherence to rules involv ing the rejection of material simply for the reason that it was not delivered at the time agreed upon, well enough in its way, causes great delays in executing work which is of great importance to the country; and for this and other reasons it is respectfully urged that the system of procuring materials to be tested may be modified so as to allow greater facilities for obtaining the exact kind of material wanted. This subject will be reverted to again before the close of this report.

The tests made during the last year have been mainly on riveted joints, and on the resistance of white and yellow pines to forces of compression in the direction of the fiber, or as used for columns, or posts. This resistance is given in various works on the subject, as it has

been determined by different experimenters. The question to be determined was whether or not the information which we have on this point will serve as a safe and reliable rule for engineers to base their calculations on, in the construction of a bridge or building.

To solve this problem a large quantity of white and yellow pine was purchased in market; the conditions to be fulfilled were that the tim ber should be sound, free from sap, large and loose knots. It was procured in April, 1881, the white pine mostly from New Hampshire, with some from Michigan, and was stored for more than a year in a dry, well-ventilated store-house, after which it was tested as single and compound columus composed of two, three, and four sticks, bolted together with keys of different thickness interposed, sometimes with different thickness in the same column, giving it a swell at the middle; 191 tests of full-sized columns were made; the most of them were of the same length, 15 feet; the pieces were dressed, and the ends squared with care, so as to give an even bearing; they were first weighed, the rings of growth counted, the grain noted, whether straight or not, and placed in the machine in a horizontal position with the greater depth vertical, so that the weight of the column should have no effect in determining its deflection; the elastic limit, in compound columns, was first determined of the pieces separately, which were afterwards assembled, and the load increased gradually till failure took place.

When only a limited number of tests have been made with carefully selected sticks of small size, there is no trouble experienced in drawing definite conclusions therefrom; but as the tests increase in number and the size of the specimens becomes larger, the difficulty of drawing conclusions increases, and with a large number of tests of specimens of large size, and with the ordinary imperfections of the timber, it is almost impossible to draw any general conclusions applicable to all timbers. It was found that the average load for sticks as large as those used was about one-half of that which is ordinarily given as the ultimate load for these woods; that the weak points are the knots, and in pieces which yield by the crushing of the fibers failure always takes place at the knots; in pieces of greater length the effect of knots is less felt, and it cannot be clearly demonstrated to what extent they influence the resistance of the column; and in very long columns, unless the knots occur near the middle of the length, they seem to have no appreciable effect in determining the direction of flexure. Some sticks were tested a second time after the lapse of a year or more, and in all cases a diminution of strength was observed on the second trial.

A second series of tests was made on yellow pine, each increment of the load being permitted to remain for five minutes and then removed, measuring the set caused thereby. Curves have been plotted showing the effect of this continuance of the load, and the effect becomes more apparent as the ultimate strength of the timber is approached.

In compound columns care should be exercised in selecting the sticks which are to form the column; of course it would be useless to place a poor with a strong stick, but it is best to place the good together and the inferior by themselves. No attention was at first paid to this disposition until experience showed the advantage to be gained by its ob

servance.

To make the effect of knots in the resistance of short posts to compression more apparent, some columns, after having been tested and their resistance determined, were cut up and specimens of shorter lengths taken and tested; the difference in the strength was very marked, as was to be expected. An oak column 168 inches long, which yielded at 4,953 pounds per square inch, showed in a specimen 32 inches long

cut therefrom 8,450 pounds per square inch, and another 7,794 pounds per square inch, which then gave way at a knot. Another post, 164 inches long, failed at 3,432 pounds per square inch, but a piece 32 inches long was cut from it which gave 6,230 pounds per square inch. A yellowpine post 143 inches long gave a resistance of 4,663 pounds per square inch, but a specimen 32 inches long was taken from it which had a resistance of 6,230 pounds per square inch. Pieces of smaller size could doubtless have been cut from each of these which would have shown still greater strength, as they might have been obtained more free from imperfections of all kinds. Knots of even small size, firm and sound, exercise an injurious effect upon the strength of timber. This was shown in a piece of spruce from which two samples were cut-one having a uniform, straight grain, the other two small knots; the strength of the former was 11 per cent. greater than the latter. A photograph gives some idea of the apparent insignificance of the knots in this case.

When we come to determine the resistance of specimens having knots to forces of compression at right angles to the fibers of the wood, we find the resistance much increased, and this increase should be taken into account when selections for this purpose are possible. The resistance of specimens of a given wood as compared with others of its kind is generally indicated by its specific gravity, but this does not always hold good. In yellow pines, some of those rich in turpentine have a high specific gravity and yet are not the strongest. The rapidity of growth will sometimes give indications of the strength. A rapid growth in oak is apt to be accompanied by an increase of strength, while the reverse is often true in yellow pine.

RIVETED JOINTS.

Testing-machines in general have not been arranged to hold conveniently and rigidly flat plates of considerable width, and consequently there are on record no great number of tests giving the proportions of resistance of such joints to the area of cross-section of metal. With the view of determining the much-needed data on this subject, both as applied to boilers, bridges, and similar structures, I instituted an extended series of experiments, commencing with the tests of ordinary specimens of the material used to determine its tensile strength and to serve as a standard of comparison for all of the succeeding tests. Afterward grooved specimens, 146 in number, were tested. At first the area of cross-section remained constant, the size of the groove varying from inch to inch, and then the area was increased. Of these preparatory tests 214 were made.

Experiments were instituted to determine the amount of friction that is caused by the pressure with which one plate is forced against its neighbor by the riveting. Iron and steel plates and inches were used, held together first with one rivet and afterwards with five rivets; and the shearing strength of the rivets determined. More than 100 tests have been made of single-riveted lap-joints of plates 1, 3, 4, §, and inch, both of iron and steel, and double-riveted lap-joints with and inch plates, and single-riveted lap-joints, with a reinforced welt, with plates of inch, both iron and steel.

A portion of a locomotive boiler which had been in service for twentyfour years was obtained from one of the railroad companies with the view of determining in what way it compared with boilers made at this time. So far as could be detected by examination it had undergone no marked change, but when subjected to stress it showed a grooving of about

inch deep. A photograph of the specimen was taken to show

the thickness to which the metal was reduced by this long-continued action.

MISCELLANEOUS TESTS.

Some iron bars which had been previously tested and showed a mean ultimate strength of 52,034 pounds per square inch, were tested again after an entire rest from eight to ten months. The mean ultimate strength after rest was 62,146 pounds per square inch. Such a bar was heated to a cherry-red heat and permitted to cool, when it was tested, and broke at 39,700 pounds per square inch, showing that the increase of strength gained by previous stress was lost by the reheating, and the iron had ceased to be as strong as it originally was.

Some 2-inch round bars of single and double refined iron which could not be tested last year for the want of proper means to hold the bars, have been tested, and show that the ultimate strength of the product of one mill was slightly less for the single refined than the double, and of the other the strength was greater.

Wrought iron I-beams have been tested to give their resistance when used as columns; and some short columns with one pin and one flat end, remnants of columns on hand, have been tested for compression.

With the means at my disposal I am able to give merely the results obtained by the testing machine. I have not the means of working up these results to show more clearly their bearing, and fit them for the practical use of others.

The provision made in the machine for holding flat bars of moderate size, or specimens of plate, are all that can be desired, but the conveniences for testing round bars of all sizes are not so perfect. The specimen, if it be of a ductile material, is diminished in size, and as the holder does not follow up the action of the specimen, the latter is not held so firmly as at first, and finally is liable to slip in the die. The importance of being able to test specimens of round bars of all sizes just as they come from the mills, was deemed so urgent that I proceeded at considerable expense to add to the machine this important and necessary part. It is made throughout of steel, and from the experience thus far had with it there seems to be little doubt of its answering the desired purpose admirably well. As yet I have prepared only a single set of dies for 2-inch bars; others will have to be added as the necessities require and the funds will permit. The cost of this new holder has been $1,309.

Mr. James E. Howard, who has had the immediate charge of the machine and of the tests made thereon, has performed his laborious duties in a manner highly acceptable to myself and the private parties who have had occasion to make use of the machine. His intelligent interest in the work, the care that he takes to insure entire accuracy of results, his quickness to observe all that takes place, and the skill with which he manages the machine, are a sure guarantee for the perfect reliability of the results obtained, and persons who have been present at the tests of their own materials, to see for themselves that every precaution is taken to insure accuracy, have expressed themselves as entirely satisfied in every particular with the manner of conducting the work.

I am indebted to Capt. John Pitman, Ordnance Department, for the chemical analysis of certain specimens of iron and steel, and for the photographs and drawings which serve to illustrate this report. The labor of preparing the latter has been performed by him cheerfully, though it has not been customary to require such work, week after week,