Canon Moseley on the Mechanical Properties of Ice. 3 



that standard. For the standard measure, two bolts were driven 

 into the wall of a room of the observatory, in the same horizontal 

 line and at the same distance from one another as the bolts in 

 the block of ice. One of these bolts had a hole sunk in its end 

 in the direction of its axis, of the same size as the holes in the 

 bolts inserted in the ice ; and the other bolt carried at its end a 

 divided plate similar to the plates on those bolts. The room, in 

 the wall of which these bolts were fixed, was preserved as nearly 

 as possible at the same temperature*. To compare with the dis- 

 tance of these bolts the distances at different temperatures of the 

 bolts in the block of ice, a rod (B, fig. 2) of dry white deal was 

 used, 5 feet 3 inches long, having for its section a square whose 

 sides were in the middle If inch in length, but tapered off at 

 the ends to 1 inch. On each end of this rod was firmly fixed a 

 brass ring, aa' } 1*83 inch in diameter. Fixed to one of these 

 rings, parallel to the axis of the rod and at the extremities of the 

 same diameter of the ring, were two plates (m, m!) of brass, whose 

 surfaces were silvered, and divided on their chamfered edges, so 

 as to be applied to the corresponding plates on the bolts in the 

 ice-block. 



Through the other ring, as also through the measuring-rod 

 itself, was passed a bolt, s s', which had at each extremity a 

 pin of hardened steel accurately fitting the holes sunk in the 

 ends of the bolts which passed through the icef. The whole 

 stick was thickly wound round with cotton-wool sewn up in linen 

 cloth, so that it could only be very slowly affected by variations 

 of external temperature. The divisions of the plates on the rod and 

 on the ends of the bolts in the ice were so adjusted as to form a ver- 

 nier measuring to the j-gW of an inch. When not in use the mea- 

 suring-rod was hung on the wall the bolts in which served as the 

 standard of measurement, so as to acquire its constant tempera- 

 ture. When used, the rod was carried out, and the pin passing 

 through the ring at one of its ends was passed into the hole 

 sunk in the extremity of the bolt projecting from one of the 

 two vertical faces of the ice-block, the plate on the ring at the 

 opposite end being at the same time brought into contact with 

 the plate on the end of the other bolt which projected from the 

 same face of the ice-block. The distance having been read off 

 by the vernier, the rod was turned round on its axis 180°, so as 

 to bring the opposite pin into the hole sunken in the one bolt in 

 the ice, and the opposite plate into contact with the plate fixed on 



* It was situated between two other rooms, which were heated with hot 

 air from the same stove, the access of which could be regulated. 



t There was an ingenious contrivance by which the insertion of the same 

 length of this pin into the hole of the bolt at each experiment was provided 

 for. 



B2 



