M. H. Fizeau on the Expansion of Solids by Heat. 31 



mity of b passes into the water 

 and carries a bulb, c. The tube 

 b also carries a branch, t, the up- 

 per end of which carries a cork 

 through which works very stiffly 

 the solid plug p. The cork in 

 t is provided with a small hole to 

 allow air to pass. Mercury is 

 poured into / until it rises to a 

 convenient height in b. The plug 

 p is adjusted and the whole held 

 very firmly in a clamp. The action 

 is obvious. At a certain tempera- 

 ture the air in c will occupy such 

 a volume that the mercury will be 

 forced up b until its surface, a, 

 begins to shut off the gas. The 

 flame of / will thereupon diminish 

 in size. By pushing the plug p 

 further down mercury will be forced 

 up b, and a consequent lowering of 

 the temperature will follow. By 

 this means the instrument can be set for any temperature with- 

 out disturbing the mercury. 



To avoid the necessity of constant 

 stirring, and to disperse the currents 

 of heated water rising from below, a per- 

 forate cone of sheet iron, as shown in 

 the accompanying figure, is supported 

 upon the bottom of the vessel containing 

 the water*. 



VII. On the Expansion of Solids by Heat, 

 By M. H. FizEAuf. 



IN the new research which I have the honour of laying before 

 the Academy, I propose to present the continuation of my 

 researches on the expansion of solids by heat, and especially of 

 crystallized bodies. 



Having observed a great number of new bodies, and having in- 

 vestigated them in various directions with a view to make evident 



* Since the above was in type, I have been informed that Bunsen also 

 has employed the expansion of air in his thermostat. There remains, 

 therefore, so little originality in my form of the apparatus, that the incon- 

 venience which would ensue to the printers of the Magazine alone prevents 

 the suppression of the above. — F. G. 



t Translated from the Comptes Rendus, May 25, 1868. 



