Propagation of Heat in Liquids. 279 



These cross-pieces are each pierced with two square 

 holes, at the distance of 1 1 inches one from the other, 

 into which the upright pillars C C enter, and the cross- 

 pieces are supported at any height that is required, by 

 means of a screw of compression. These screws are 

 represented in the figure. 



The cross-piece F G, which is represented in pro- 

 file, is 17 inches in length, and \\ inches thick, and 3 

 inches in breadth. It is pierced in the middle by a 

 cylindrical hole of 2 inches in diameter. 



The cross-piece D E is 17 inches in length by \\ 

 inches in thickness. It is 3 inches wide at each end and 

 6 inches in the middle,, where it is pierced by a circular 

 hole 5 inches in diameter. 



The cross-piece D E serves to support the annular 

 vessel H I, of which a vertical section passing through 

 its axis is seen in the figure. This vessel, formed of 

 thin brass plates, is 5 inches in diameter without, 3 

 inches in diameter within, and 27^ inches in depth. 

 This vessel is filled with water during the experiments 

 to the height of 2^ inches ; and its form is such, that, if 

 the water that it contains were frozen into a solid mass 

 of ice, this piece of ice would have the form of a tube 

 or perforated cylinder of i inch in thickness and i\ 

 inches high by 5 inches in diameter without. Its cylin- 

 drical cavity would be precisely 3 inches in diameter. 



K L is a vertical and central section of a cylindrical 

 vessel of tin of 10 inches in diameter by 4^- inches in 

 depth. It is filled with water to the height of 4 inches, 

 as it is seen in the figure. 



The cross-piece D E is placed at such a height that 

 the bottom of the annular vessel H I is plunged a 

 quarter of an inch under the surface of the water con- 

 tained in the great cylindrical vessel K L. 



