2 Canon Moseley on the Mechanical Properties of Ice. 



For 80° R., or for the whole dilatation between the freezing 

 and boiling temperatures, this gives the coefficient 



•005142*. 



And as there are 180° of Fahrenheit between these tempera- 

 tures, the coefficient of the dilatation of ice for 1° F. is 



•00002856. 



The experiments of M. C. Schumacher were the most nume- 

 rous aud the most complete. They were conducted as follows. 



By pouring water which had been previously boiled into a 

 wooden trough or mould, and leaving it on trestles exposed to 

 the air for twenty-four hours, it was frozen into a solid block of 

 ice tolerably free from air-bubbles, which, when brought into a 

 regular shape and rounded at its angles, was 6 feet 3 inches 

 long, 6^ inches deep, and 6 inches wide. A longitudinal sec- 

 tion of this block of ice is shown in Plate I. fig. 2 A, and a 

 transverse one in fig. 3. 



To have fixed points on the block from which to measure its 

 dilatation, two steel bolts (b and b 1 ) were made to pierce the 

 block from side to side near its ends, and were frozen into it. 

 Each of these bolts had fixed across one end a silvered brass 

 plate (n, n r , fig. 2) with divisions ; and the other end of each bolt 

 was pierced in the direction of its axis by a cylindrical hole (p, p)'. 

 The two bolts had their divided plates on opposite sides of the 

 block, and also the holes pierced in their extremities. In the 

 upper surface of the block of ice three equidistant holes were 

 bored (t' } t", t"') halfway through its thickness, into each of which 

 a thermometer was frozen. The bulb of each thermometer was 

 contained in a cavity of the ice larger than itself, so as to be 

 surrounded by air, all communication between which and the 

 external air was cut off by the stem being frozen into the ice. 

 The block of ice was then slung, at about 8 feet from the 

 ground, by two cords passed round it near its ends, to a beam 

 supported on trestles (fig. 1) which stood on one of the projec- 

 tions of the peristyle of the observatory, where it was exposed to 

 the free influence of the external temperature. 



To determine the different distances of the two bolts at differ- 

 ent temperatures of the block of ice as shown by the thermome- 

 ters, it was necessary to have, 1st, a standard measure not affected 

 by variations of temperature, with which to compare these dis- 

 tances, and, 2ndly, some reliable means of comparing them with 



* Of other solids, the most dilatable are lead (whose coefficient of 

 dilatation between the same limits of temperature is "002848) and zinc 

 (whose coefficient is *002976) ; the dilatation of ice for a given increase 

 of temperature is therefore nearly twice as great as that of any other 

 known solid body. 



