298 



Messrs. Sorby and Butler on the Structure oj [Feb. 18, 



temperature rose above 80° it was so very extraordinary that it was not 

 until after having performed the experiment over and over again that Mr. 

 Sorby felt confidence in the results. This will not be thought surprising 

 when we state that from 31° to 32° the apparent expansion of the liquid 

 is no less than one-fourth of the bulk it occupies at 31° ; the length of 

 the column increasing for that single degree from to -f^ inch. 

 This is about 780 times as great as the expansion of water would be, and 

 even G9 times as much as that of air and permanent gases. It was not 

 possible to ascertain the amount of expansion above 32° C, because the 

 cavity was quite filled at that temperature. If the expansion increase at 

 the same increased rate, the liquid would soon occupy several times as much 

 space ; but it seems very probable that before then it would pass into the 

 state of gas. At all events it appears as if this enormous rate of expansion 

 indicated a close approach to a fresh physical condition. The following 

 Table gives the results of the experiments ; and it has been found, by drawing 

 them as a curve, that their general relations indicate that there cannot be 

 any serious error ; but at the same time, considering all the circumstances, 

 they must only be looked upon as tolerably good approximations to the 

 truth. 



Temperature. Volume. 



OC. 100 



l?i 109 



20 . 113 



25 122 



28 130 



29 139 



30 150 



31 174 



32 217 



The apparent expansion of the liquid is doubtless to some extent in- 

 creased by the condensation of the gas, as the space occupied by it is 

 diminished. When in the highly expanded condition this liquid appears 

 to be remarkably elastic. Berthelot has shown, in his paper on forced 

 dilatation*, that the force with which liquids adhere to the interior of a glass 

 tube is sufficient to prevent their contraction to the normal volume, if 

 they have been heated so as to expand and quite fill the tube, and then 

 cooled to a temperature below that requisite to fill it. This fact must 

 always be borne in mind in studying fluid-cavities, and explains why the 

 bubbles, as it were, hesitate to return, and then make their appearance with 

 a sudden start. Such a forced dilatation is very remarkable in the case 

 described ; for though it was requisite to raise the temperature to 32° C. to 

 fill the cavity, no vacuity was formed until it fell to 31°; and therefore it 

 seems as if the force of cohesion were sufficient to stretch it to considerably 

 * Annates de Chirnie ser. 3. t. xxx. p. 232. 



