165 



flank of the Alps they had been discovered by M. Elie de Beau- 

 mont in beds of the age of lias. 



Two Communications have been presented to us, one from the 

 pen of Mr. Babbage, the other of Captain Basil Hall, R.N., on the 

 Temple of Serapis at Puzzuoli, one of the most extraordinary build- 

 ings in Europe ; beautiful as a work of art, interesting as an object 

 of antiquity, but to the geologist more especially valuable, as ex- 

 hibiting a variety of complex natural pheenomena, which, though 

 they have taken place in times comparatively modern, it is exceed- 

 ingly difficult to explain according to the known laws of nature. 



Of the solutions which have been proposed by different authors*, 

 not fewer than twenty in number, and most of them authors of emi- 

 nence, it is impossible to give even a sumraai'y within the time al- 

 lowed me. The merit of Mr. Babbage's paper, as far as original ob- 

 servation is concerned, consists principally in his notice of various 

 stalactitical deposits, and his examination of their different charac- 

 ters and modes of production. 



Mr. Babbage describes in detail all the appearances of this tem- 

 pie, and then inquires into the causes of the extraordinary revolu- 

 tion's which it must be admitted on all hands to have undergone : the 

 principal difficulty, you are aware^is to account for the erosion of the 

 columns by lithophagous animals, from the height of 11 feet to 19 

 above their base, the remaining parts being intact. 



Mr. Babbage is of opinion that the building stood at first very 

 nearly at its present level. Assuming that since that period it has 

 both subsided and risen again, and that considerable changes have 

 taken place in the relative levels of the land and sea in its vicinit}' ; 

 he explains these circumstances by supposing the edifice to have 

 been built upon the surface of matter at a high temperature, which 

 matter contracted afterwards by slow cooling ; that at a still subse- 

 quent period a fresh accession of heat produced a new expansion, and 

 that in this way the temple was gradually restored to its original level. 



To suppose and illustrate his reasoning, the author has constructed 

 a Table (founded on experiments made in America,) showing in 

 feet and decimals what would be the amount of expansion in beds 

 of granite from 1 to 500 miles thick at various temperatures ; toge- 

 ther with a formula for calculating the amount of expansion in si- 

 milar volumes of marble and sandstone ; this Table has a collateral 

 claim to notice, as being the first worked out by the calculating en- 

 gine with a view to publication. 



It appears to me, that in applying the calculation, it is very ne- 

 cessary to take into account three elements which have been over- 

 looked. 



1. How far under the supposed conditions expansion would be 

 counteracted by pressure? 



* Among these may be mentioned Barthelemy, Boue, Brieslak, Brocclii, 

 Cochin, Billiard, Daubeny, Desmarest, Desnoyers, Forbes, Goethe, Hoff, 

 De Jorio, Lyell, Pini, Prevost, Nicolini, Raspe, and Dr. Robertson. 



