254 



same formation has been traced together with lithodomous perfora- 

 tions by Dr. Carlo Gemmellaro and Baron v. Waltershausen along 

 the sea-shore as far north as Taormina, beyond the volcanic region 

 of Etna. From these and other data enlarged upon in the memoir, 

 Sir C. Lyell concludes, first, that a very high antiquity must be 

 assigned to the successive eruptions of Etna, each phase of its vol- 

 canic energy, as well as the excavation of the Val del Bove, having 

 occupied a lapse of ages compared to which the historical period is 

 brief and insignificant ; and secondly, that the growth of the whole 

 mountain must nevertheless be referred, geologically, to the more 

 modern part of the latest Tertiary epoch. 



II. "On some Thermo-dynamic Properties of Solids." By J. 

 P. JOULE, LL.D., F.R.S. &c. Received April 22, 1858. 



(Abstract.) 



A resumt of the greater part of this paper has already appeared 

 in the ' Proceedings ' for January 29, June 18, and November 26, 

 1857. The author has since examined the expansion by heat of 

 wood cut across the grain, which, as well as that cut in the direction 

 of the fibre, he finds to be increased by tension and decreased by 

 moisture. "When a sufficient quantity of water has been absorbed 

 the expansibility by heat ceases, and wood is contracted in each di- 

 rection by rise of temperature. Nevertheless, when wood, saturated 

 with water, is weighed in water of different temperatures, the result 

 shows cubical expansion of the substance of the wood by heat. The 

 inference drawn by the author from these facts is, that the contraction 

 of the dimensions of wet wood is owing to the action of heat in di- 

 minishing the force of capillary attraction, and that thus the walls of 

 the minute cells and tubes of the woody structure are partially re- 

 lieved from a force which thrusts them asunder, a small quantity of 

 water exuding at the same time. In the case of wet wood which 

 contracts by heat, he finds, in accordance with Professor Thomson's 

 formula, that a rise of temperature is produced by the application of 

 tension. In conformity with the deductions of the same philosopher, 

 the author has also been able to detect experimentally the minute 

 quantity of heat absorbed, in bending or twisting an elastic spring, 

 arising from the diminution of the elastic force of metals with a rise 

 of temperature. 



