from an Increase of Temperature. 



361 



Fig. 3. 



A 



always in the same position in the instrument, p is the square 

 pin fitting into the socket, and moved by the screw G, Fig. 1. 

 The upper part of the rod was kept in the proper position, by 

 means of slender springs of wire, which pressed a small roller against 

 the front of the case, so that the upper stud always stood at the 

 same distance from the object-glass of the upper micrometer. This 

 is shewn by Fig. 4, which is a section of the upper part of the 

 double case of the full size. A is the upper end of the rod 

 under experiment. R the roller pressing on the front of the 

 double case. SS the space through which the steam passes. B 

 the upper stud opposite to the window and upper micrometer M. 

 CC the back spring, E one of the side springs. F the cover of the 

 top, which is double ; and the space between the upper and un- 

 der plate is stuffed with cotton. T the bulb of the upper ther- 

 mometer. V is the upper pipe, by which any vapour coming 

 from the enclosed rod may escape, when it is wished to allow the 



