On Thermodynamic and Met amorphic Functions, fyc. 407 



orifice and driven down with a hammer by means of the 

 plug P. The bruised and broken ice 

 separates at x, one portion going to Fig. 9. 



the right, the other to the left. Dri- 

 ving the ice thus into the mouldy piece 

 after piece, it is finally filled. By 

 removing the rectangle RE, the two 

 halves of the mould are then separated, 

 and a perfect ring of ice is found within. 

 Two such rings soldered by regelation 

 at a are shown in fig. 9. It would be 

 easy thus to construct a chain of ice. 

 An hydraulic press may of course be 

 employed in this experiment, but it is 

 not necessary; with the hammer and 

 plug beautiful rings of ice are easily 

 obtained by the regelation of the crushed 

 fragments. 



I have now to add the descrip- 

 tion of an experiment which suggested 

 itself to my ingenious friend Mr. Duppa 

 when he saw the ice-rings just referred 

 to, and which was actually executed by 

 him yesterday (the 16th) in the laboratory of the Royal Institu- 

 tion. Pouring a quantity of plaster of paris into a proper vessel, an 

 ice-ring was laid upon the substance, an additional quantity of 

 the cement being then poured over the ring. The plaster " set," 

 enclosing the ring within it : the ring soon melted, leaving its per- 

 fect matrix behind. The mould was permitted to dry, and, molten 

 lead being poured into the space previously occupied by the ice, a 

 leaden ring was produced. Now ice can be moulded into any shape: 

 statuettes, vases, flowers, and innumerable other ornaments can 

 be formed from it. These enclosed in cement, in the manner 

 suggested by Mr. Duppa, remain intact sufficiently long to enable 

 the cement to set around them ; they afterwards melt and dis- 

 appear, leaving behind them perfect plaster moulds, from which 

 casts can be taken. — J. T. 



LVII. On Thermodynamic and Metamorphic Functions, Disgre- 

 gation, and Real Specific Heat. By W. J. Macquorn Ran- 

 kine, C.E. t LL.D., FR.SS.L. $ E* 



1. r ■ THE following paper relates to certain differences which 

 -L Professor Clausius considers to exist between his views 

 and mine of some questions in thermodynamics — differences 

 * Communicated by the Author. 



