The following table contains the values of the Moduli of Rupture and of Elasticity deduced from the whole series of experiments:

W 13

4 A b d s

Calculating E=; for heavy loads and considerable deflections, the following figures were obtained for this pseudo-modulus:

TABLE II:- Values of E at one-third to one-half total load.

As a general rule, the maximum figure was given at one-third, rarely at one-half, and about as often at the beginning of the test. The latter case occurred most frequently with the unseasoned timber.

Heavy loads, long applied, produced fracture of pieces, the companions to which resisted considerably more when the load was steadily increased up to the moment of fracture. The maximum permanent load was apparently something less than one-third and probably greater than one-half the maximum load which could be sustained under ordinary test.

A set of four yellow pine beams of large section was tested to determine the value of the Modulus of Elasticity in large timbers, and also to ascertain whether experiments upon small sticks, such as are usually tested, may be relied upon to give correct values of this coefficient.

The following figures were obtained:

TABLE IV. — Elasticity of Yellow Pine Timber.

1 Average of trials at 7=150 to 200.

2 Average of trials at 7= 150 to 200, and beams in different positions.

Nos. 1 and 2 of this lot were of poor quality; the latter, particularly, was somewhat shaky, yet it fairly represents much of the timber which finds its way into important constructions.

From the whole series of experiments, of which the briefest possible statement of the results obtained is here given, the conclusion may be drawn that:

The elasticity of yellow pine timber as used in construction is very variable, the modulus varying from one to three millions, the average being about two millions in small sections, and a little above one and a half millions in large timber (Tables I, IV).

The highest values are as often given by green as by seasoned timber, and that, under sixteen square inches section and fifty-four inches length, at least, the magnitude of the modulus of elasticity is independent of the size of the piece (Table I).

The density of the wood does not determine the modulus; since the figure varies sometimes directly and sometimes inversely with the density, even where the wood is as nearly as possible in the same condition as to seasoning.

A high modulus usually accompanies high tenacity and great transverse strength, but it is not invariably the fact that maximum ultimate strength is accompanied by initial stiffness (Table I).

The pseudo moduli, determined by taking considerable deflections, are usually not greatly different from those determined from

small deflections and light loads. The values of these moduli may increase with increase in deflection (Table III).

An inspection of the woods tested plainly indicates, in the opinion of the writer, that the density of the pines is so considerably modified by the amount of pitch contained in the sap channels that it cannot be regarded as indicative of the strength of the timber. Where quite free from sap, the wood usually exhibits increase of strength and elastic resistance to deflection, with increase of density.

The strength of timber, otherwise similar, is greatly affected by its structure, and the resistance offered to stresses applied transversely is greatest when the sections of the timber taken transversely exhibit most nearly vertical lines of grain.

The modulus of rupture by transverse stress varies, for yellow pine, from R10,000 to 17,000, the highest values being usually obtained from well-seasoned wood. An average value may be taken as R= 13,000 for good timber, which in the formula W = gives C8,666 pounds, or, practically, W9,000, for good yellow pine.

The modulus of rupture varies as irregularly, and with as little regard to size or density of the material as does the coefficient for elasticity.

In the use of such materials, the only safe course for the designing and constructing engineer is evidently to adopt a moderate value of the modulus in proportioning his work, and by careful inspection and test to secure the rejection of all material which is not of good quality.

Careful inspection may sometimes lead to the selection of material-like the Navy Yard stock here described-twenty-five per cent. superior to the average of good timber, and fifty per cent. more valuable than the lower grades such as are often sold in our markets.

[For the complete paper see Journal of the Franklin Institute, September, 1880].

THE VELOCITY OF SHOT. By ALFRED M. MAYER, of Hoboken, N. J.

ABOUT a year ago, I determined to make a series of experiments with an undeniably accurate chronoscope, which would give direct measures of the velocity of fowling-piece shot of various sizes. At that time, I was not aware that any determination of this kind had ever been made, though similar ones on the velocities of the balls of ordnance and rifles were numerous. Thus I began my work entirely free from preconceived ideas as to what the experiments would reveal. It was only toward the end of my work, when on a visit to my friend Professor Rice, of the United States Naval Academy, that the professor told me that he had made a short series of similar experiments with a Le Boulangé chronoscope, and had published them in the "Rod and Gun" in July, 1875. This paper I then read, and I here reprint it as an appendix to my paper. My attention has subsequently been called to the works of other experimenters in the same direction; of these I have taken references, but have purposely avoided reading them.

I have made this preamble to my paper to show that my experiments are to be taken as entirely independent of other similar work, for I was not guided nor influenced during my experimenting by a knowledge which might cause me to reject certain experiments as erroneous, because they did not give results which I had thought they should have given; for no matter how conscientious an experimenter may be, he is sometimes influenced by preconceived notions, and unwittingly desires his experiments to bring out certain results. I have always in my work endeavored to avoid this mental prejudice, and have therefore, whenever possible, worked in this manner: viz., I write down the numbers given by the experiments as they are successively made, and do not reduce or compare them till after the whole series has been finished. The reader will therefore find in my results apparent anomalies, even contradictions, or, if you please, absurdities. These anomalies are those numbers which always catch the eye of hian who does not know, from experience, the difficulties and exhausting toil of a protracted series. of delicate experiments; and on these anomalies he will dwell to the exclusion of what, in the main, the experiments conclusively show. To such I say, with the experience of twenty-five years of experimenting: make the experiments for yourself and do better,