179 



that he is ready to admit the possibility that it nniy, in many instances, 

 be separated from the water^ and not be derived from an independent 

 source. 



To those, however, who refuse to admit volcanic action to be a pro- 

 cess of oxygenation, he says, such a mode of explaining the emission 

 of nitrogen would seem to remove the difficulty only one step further, 

 since it still remains to be shown why spring water, which is in ge- 

 neral impregnated more fully with oxygen than nitrogen gas, should, 

 in these cases, disengage chiefly the latter. He also adds, that in 

 none of the warm springs in the neighbourhood of Naples does nitro- 

 gen appear to be evolved in any notable quantity ; and that the warm 

 springs of Ischia are destitute of ail gaseous impregnation : and in 

 conclusion, whilst admitting that the hot springs of Campania fur- 

 nish no positive confirmation of the connexion between volcanic pro- 

 cesses and the evolution of nitrogen, the author contends, on the other 

 hand, that they suggest no facts which can set aside the evidence in 

 favour of that position, which the production of ammonia within the 

 volcano itself appears to furnish. 



A letter was afterwards read, from Lieut. Freyer, R.N., addressed 

 to Charles Lyell, Esq., P.G.S., on the appearance of elevation of land 

 on the west coast of South America. 



The localities alluded to in this letter are Arica, lat. 18° 26' south, 

 the Island of San Lorenzo in the Bay of Callao, and Valparaiso. 



Mr. Freyer states, that on his first arrival at Arica he was struck by 

 finding shells, in very great abundance, at considerable heights above 

 the present level of the sea. To the north of the town the coast is 

 low, with a shingly beach and sandy plains, no rock being exposed ; 

 but he here found shells of existing species ten or twelve feet above 

 high-water mark. On the south are interesting sections, consisting 

 of innumerable thin beds of red sandstone and gypsum, resting upon 

 shale, in which fragments of fossil shells were noticed. The bold pro- 

 montory called the Morro of Arica is formed by the dislocation and 

 elevation of this sandstone to the height of about 400 feet, by a mass 

 of basalt, porphyry, and pitchstone, which pass insensibly into each 

 other. Near the summit of the Morro the sandstone contains layers 

 of a salt, consisting of chlorine 3 1 'G, sodium 3 1 "6, sulphuric acid 1 4*0, 

 lime 9"45, potash and magnesia 9*0, insoluble (silex) 4*0*. South 

 of the Morro the sandstone and gypsum beds have a small southerly 

 dip, and form indistinct terraces towards the shore. On these ter- 

 races, wherever the rock is exposed, Balani and encrusting Millepora 

 are found. At the height of about twenty or thirty feet above the sea 

 they are as abundant, and almost as perfect, as on the shore ; at up- 

 wards of fifty feet they still occur, but abraded by the sand con- 

 stantly blowing over them ; and there are traces of them at still 

 greater heights. In the island of San Lorenzo in the Bay of Callao, 

 Mr. Freyer found, at considerable heights, Concholepas, Pecten pur- 



* The author states that this analysis was made by his friend Major 

 Emmett, R.E. 



Q 2 



