280 Inquiries concerning the Mode of the 



In the axis of this last vessel is placed a small hemi- 

 spherical cup of wood 2 inches in diameter without and 

 ^ of an inch thick. It is kept in its place by a short 

 vertical tube of tin, soldered to the bottom of the cylin- 

 drical vessel K L, into which the stalk of the cup fits 

 tightly. 



The middle of the cavity of this cup is occupied by 

 the bulb of a small mercurial thermometer of great sen- 

 sibility. Its tube, which has an ivory scale, is laid down 

 horizontally, and fixed in one side of the cup, through 

 which the tube passes, in such a manner that the lowest 

 part of the bulb is elevated ^ of an inch above the 

 bottom of the cup. The diameter of the bulb being 

 -j\ of an inch, and the hemispherical cup having \ inch of 

 radius within, it is evident that the upper part of the 

 bulb is T Vof an inch below the level of the brim of the 

 cup that contains it. To avoid charging the figure with 

 too many details, the scale of the thermometer is not 

 drawn, but the tube is distinctly represented. 



The horizontal cross-piece F G serves to support a 

 very essential part of the apparatus, which remains to be 

 described. 



This cross-piece supports, in the first place, a vertical 

 tube of wood, M, 6 T \ inches in length and 2 inches in 

 diameter without. Its interior diameter is i^V inch. 

 This tube is supported by a projecting collar (repre- 

 sented in the figure), n\ inches in diameter, which rests 

 on the cross-piece F G. It is a vertical and central sec- 

 tion of this tube that is represented in the figure, and it 

 is dotted in order to distinguish it from the surrounding 

 parts of the apparatus. 



The lower part of this tube is plunged -^ of an inch 

 under the surface of the water in the large cylindrical 



