430 MEMOIR OF THE LATE DR THOMAS CHARLES HOPE. 



the first on the 23d of January, the last on the 3d of April. The author, from 

 the action of different re-agents on infusions of these flowers, established the 

 existence in each of a distinct proximate principle, which, however, he had been 

 unable to exhibit in a separate state ; to these he gave the name of C'amellme, 

 Magnolme, and Chrysanthemine. He shewed, also, that notwithstanding the fine 

 white of the petals of Camellia Japonica, they contained much iron. 



The second paper, his last corammiication, was read on the 1st of May 1843, 

 the verj^ last time that Dr Hope was ever at the meetings of our Society. It 

 is styled "An Attempt to explain the Phenomena of the Freezing Cavern at 

 Orenburg." 



This cavern is described by Sir Rodeeick Murchison, as one of several 

 occin-ring in a low hill of Gypsum. In winter, the air of this cavern feels warm 

 to those who enter it ; but in summer an intensely cold air issues from it. This 

 has been explained by Sir John Heeschel, as being produced by the long time 

 the wiivex of heat and of cold take to penetrate to the interior of the cavern — 

 each requiring six months to penetrate to that depth ; just as Saussuee found, 

 that it required, at Geneva, six months for the heat of summer, or the cold of 

 winter, to penetrate to the depth of '2Q\ feet. While admitting this general ex- 

 planation, Dr Hope considered that it would require something more to explain 

 the forcible issue of such cold air during the summer months ; and he makes an 

 ingenious conjecture, on the part performed by the air cooled in the fissures, 

 described as existing in the inmost recesses of the cavern, in producing that 

 phenomenon. 



The subject is very intei-esting though obscure ; but I may observe that such 

 streams of cold air are not peculiar to the Orenburg cave. Streams of air, cooled 

 from 15° to 34° below the external air in the shade, are known to issue from the 

 crevices of the small artificial hill at Rome, named Monte Testaccio j from the 

 limestone grottos of Cesi, in the Roman states, so well described by Saussuee, in 

 Jrmrnal de Physique for 1776 ; from the caves in the sandstone hiU, on which is 

 perched the miniature republic of ;S'(//( Marino j from the Cantines in the potstone 

 rock near Chiavenna ; from the cavenis of Caprino, on the Lake of Lugano ; 

 and from the calcareous caves of Plergisweil, at the base of Mont Pilate, nearly 

 opposite to Lucerne. What is still more extraordinary, such cold caves exist in 

 countries the seats of not yet extinguished volcanic fire. Sir Wii,liam Hamilton 

 describes the cold Avinds issuing from the cave of Ottajano, at the base of Vesuvius; 

 and in the Isle of Ischia, the air which issues from the Ventarola of Funera is as 

 cold as 43° F., when a thermometer in the shade, without the cavern, is at 58° — 

 (See Saussnre, Voyages danslcs Alpes, III. 1405.^ 



Such are the chief contributions of Dr Hope to physical science. 



It has been alleged that they are fewer and less important than we had 

 reason to expect, from the long period during which he filled the Chemical Chair, 



