Things not generally Known. 



in which it was originally built ; but that the sea rose, sur- 

 rounded it to a height of at least twelve feet, and again re- 

 tired ; but the elevated position of the sea continued sufficiently 

 long to admit of the animals boring the pillars. This view can 

 even be proved historically; for Niccolini, in a memoir pub- 

 lished in 1840, gives the heights of the level of the sea in the 

 Bay of Naples for a period of 1900 years, and has with much 

 acuteness proved his assertions historically. The correctness 

 of Russager's opinion, he states, can be demonstrated and re- 

 duced to figures by means of the dates collected by Niccolini. 



See Jameson s Journal, No. 58. 



At the present time the floor is always covered with sea- water. 

 On the whole, there is little doubt that the ground has sunk 

 upwards of two feet during the last half -century. This gradual 

 subsidence confirms in a remarkable manner Mr. Babbage's 

 conclusions drawn from the calcareous incrustations formed 

 by the hot springs on the walls of the building and from the 

 ancient lines of the water-level at the base of the three columns 



that the original subsidence was not sudden, but slow and 

 by successive movements. 



Sir Charles Lyell (who, in his Principles of Geology, has 

 given a detailed account of the several upfillings of the temple) 

 considers that when the mosaic pavement was re-constructed, 

 the floor of the building must have stood about twelve feet 

 above the level of 1838 (or about 11 5 feet above the level of the 

 sea), and that it had sunk about nineteen feet below that level 

 before it was elevated by the eruption of Monte Nuovo. 



We regret to add, that the columns of the temple are no 

 longer in the position in which they served so many years as a 

 species of self-registering hydrometer : the materials have been 

 newly arranged, and thus has been torn as it were from history 

 a page which can never be replaced. 



THE GROTTO DEL CANE. 



This " Dog Grotto" has been so much cited for its stratum 

 of carbonic-acid gas covering the floor, that all geological tra- 

 vellers who visit Naples feel an interest in seeing the wonder. 



This cavern was known to Pliny. It is continually exhaling 

 from its sides and floor volumes of steam mixed with carbonic- 

 acid gas ; but the latter, from its greater specific gravity, accu- 

 mulates at the bottom, and flows over the step of the door. 

 The upper part of the cave, therefore, is free from the gas, 

 while the floor is completely covered by it. Addison, on his 

 visit, made some interesting experiments. He found that a 

 pistol could not be fired at the bottom ; and that on laying a 

 train of gunpowder and igniting it on the outside of the ca- 

 vern, the carbonic-acid gas " could not intercept the train of 



