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Testing Machines (Used for the accurate testing) (II)

machines used for the accurate testing of iron, steel and other materials used in constructive work. The problem which these machines are intended to solve is the adjustment with certainty of a safe margin of strength with a minimum of weight, which can be determined only by experimental tests on full sized sections of the materials used in the construction.

One method is to use machines designed to test small sample pieces under such conditions that the breaking strength of the test-piece is measured by the machine, and from the figures thus obtained is calculated the strength per square inch of the full-sized constructive material.

A common feature of such machines is the common steelyard balance, supported by knife edges. There are several machines of this class, some of them built up to 100,000 pounds capacity and over.

The hydraulic testing machine, invented by A. H. Emery, was originally used at the United States arsenal at Watertown, Mass. The greatest peculiarity of the Emery testing machine is the method by which the stress produced on the piece tested is conveyed to the scale and accurately weighed by mechanism that is entirely without friction, and hence responds to the same increment of load regardless of the amount of strain on the specimen. This result is accomplished by receiving the load against a flat closed cylinder called the hydraulic weighing head. One of the government experi ments with this machine was the breaking by tension of a forged iron link 5 inches in diameter between the eyes, at a strain of 722,800 pounds, and immediately after a horse-hair 7 1000 of an inch in diameter was slowly strained, and, after stretching 30 per cent., snapped under the recorded strain of 16 ounces.

TEST OATH, an oath prescribed by the United States Congress July 2, 1862, to be taken by persons in the former Confederate States appointed to office under the National government. The text was as follows: "I, A. B., do solemnly swear (or affirm) that I have never voluntarily borne arms against the United States since I have been a citizen thereof; that I have voluntarily given no aid, countenence, counsel, or encouragement to persons engaged in armed hostility thereto; that I have neither sought, nor accepted, nor attempted to exercise the functions of any office whatever, under any authority or pretended authority in TESTUDINIDE hostility to the United States; that I have not yielded a voluntary support to any pretended government, authority, power, or constitution within the United States, hostile or inimical thereto. And I do further swear (or affirm) that, to the best of my knowledge and ability, I will support and defend the Constitution of the United States against all enemies, foreign and domestic; that I will bear true faith and allegiance to the same; that I take this obligation freely, without any mental reservation or purpose of evasion, and that I will well and faithfully discharge the duties of the office on which I am about to enter, so help me God."

TEST PAPERS, in chemistry, are made by dipping unsized paper into an alcoholic solution of a vegetable coloring matter which changes color when exposed to the action of an acid or alkaline solution. The paper, after being gently dried, is cut into slips of a suitable size.

Hence, by dipping the appropriate test papers into any solution, one can ascertain whether it is acid, alkaline, or neutral. Litmus and turmeric are most commonly used as the coloring matters; litmus for the detection of acids, and turmeric for that of alkalies. Test papers are also employed for detecting sulphuretted hydrogen, etc., and for such a purpose the paper must be dipped in the solution of an appropriate substance.

Thus acetate of lead paper becomes black in presence of sulphuretted hydrogen, while starch paper becomes blue when touched with iodine.

TESTUDINARIA (so named from the resemblance which the great, rugged, cracked root of the plant bears to the shell of a tortoise), in botany, the elephant's foot or Hottentot's bread; a genus of Dioscoreaceæ, akin to Dioscorea, but with the seeds v winged only at the tip, instead of all round. Rootstock above ground sometimes four feet in diameter.

Stems occasionally 40 feet long; flowers small, greenish-yellow. T. elephantipes is the common elephant's foot or Hottentot's bread. The rootstock is a large, fleshy mass, covered with a thick bark, cracked deeply in every direction. The Hottentots in time of scarcity made use of the fleshy inside of the root as a kind of yam.