408 Miscellanies. 



29. Abstract of a theory of the elevation and depression of the 

 earths crust, hy variations of temperature, as illustrated by the Tem- 

 ple of Serapis. — •From the Proceediugs of the Geological Society 

 of London, Vol. II., letter from Charles Babbage, Esq. March 12. — 

 O. P. H. 



The author describes the present state of the Temple, and gives 

 the measurement of three marble columns, which from the height of 

 eleven feet, to that of nineteen feet, (8) are perforated on all sides 

 by the Modiola Lithophaga of Lamarck, the shells of that animal 

 remaining in the holes formed by them in the columns. A descrip- 

 tion is then given of the present state of twenty seven portions of 

 columns, and other fragments of marble, and also of the several in- 

 crustations formed on the walls and columns of the temple. 



The conclusions at which the author arrives, are : 



1. That the temple was originally built at, or nearly at the level 

 of the sea, for the convenience of sea-baths, as well as for the use of 

 the hot spring, which still exists on the land side of the temple. 



2. That at some subsequent period the ground on which the tem- 

 ple stood subsided slowly and gradually ; the salt water entering 

 through a channel which connected the temple with the sea, or by 

 infiltration through the sand, mixed itself with the water of the hot 

 spring containing Carbonate of Lime, and formed a lake of brackish 

 water in the area of the temple, which, as the land subsided became 

 deeper, and formed a dark incrustation. 



The proofs are, that sea-water alone does not produce a similar in- 

 crustation ; and that the water of the hot spring alone produces an 

 incrustation of a different kind ; also that Serpulce are found adher- 

 ing to this dark incrustation ; and that there are lines of water-level 

 at various heights, from 2-9 to 4*6 feet. 



3. The area of the temple was now filled up to the height of 

 about seven feet w;ith ashes, tufa, or sand, which stopped up the 

 channel by which sea-water had been admitted. The waters of the 

 hot spring thus confined, converted the area of the temple into a lake 

 from which an incrustation of Carbonate of Lime was deposited on 

 the columns and walls. 



The proofs are, that the lower boundary of this incrustation is 

 irregular, whilst the upper is a line of water-level, and that there are 

 mariy such lines at different heights ; that salt water has not been 

 found to produce a similar incrustation ; that the water of the Piscina 

 Mirabile which is distant from the sea, but in this immediate neigh- 



