KKKKCT OK KXI'ANSIOX O\ S1I KIN K A( IK, KTC.
In Fig. 79 the parts are indicated "by letters as follows:
A, expansion and contraction-end equalizer; B, spring-clasp; I), flow-off recess; IS, spring-clasp iron; P, lever-fulcrum bearing; II, casting-pin clasp-opening; K, removable casting-pin.
The levers of this apparatus are so delicately mounted as to be moved by a breath. As already stated, for every inch travel of the long" arm, the short arm, moved by the actual expansion or contraction, travels three thirty-seconds of an inch in the straight line, The diagrams, Fig's. 74 and 75, pages $S<; and 3<jo, were constructed by platting the sum of the readings given by the pencils at the two ends of the apparatus in straight lines, and consequently give only the total longitudinal expansion and contraction, without indicating rate or alternations. But the apparatus cau be employed, with the aid of the float or clock, etc., shown in the figures, to record curves. For a straight line record, the face-plate, A, Pigs. 76 and 77, is held stationary. To obtain curve's, it is gradually lowered at. any desired rate by means of the float B, in the receptacle, I), Pig. 77, a constant head of water being maintained in the reservoir, IS, by a supply from a suspended vessel at F, and un overflow-pipe, II. A specially arranged strong spring clock might be used instead of the float B, to lower this fa'ee-boanl uniformly, so as to elTiTt the same end, and with either plan introduce into the results the element of time. Incidentally, such experiments ought, to settle the question whether there HIV, as has been declared, two periods <»f expansion in east iron when it is moling, after the liquid metal lias " fro/en," or .solidified. f