Overthrow of the Logan Stone in Cornwall. 313 



believe, the Orchard Well. It hail been some time in disuse, 

 but has more lately been cleaned out and deepened, and is 

 now about fifty-six feet to the bottom. The solid contents of 

 a pint of this water examined in London were : 



Carbonate of lime ... 1 "6 gr. 



Sulphate of lime .... 14 - 5 



Sulphate of magnesia . 1 2-4 



Sulphate of soda .... 3'7 



Muriate of soda .... 97"0 



129-2 

 Besides which, the water contained a portion of carbonic acid; 

 and a small quantity of peroxide of iron had settled to the 

 bottom of the bottle. 



On adding sulphuric acid to a portion of this water in quan- 

 tity abundantly sufficient to decompose all the salts subject to 

 its action, and boiling such acidulated water in a Florence flask, 

 with a leaf of gold for half an hour or an hour, the gold either 

 in part or entirely disappeared, and a solution was obtained, 

 which when tested by proto-muriate of tin gave a deep pur- 

 ple tint. Hence the presence of nitric acid, originally, in the 

 water was inferred; and, that no mistake might occur, a solu- 

 tion was made in pure water of all the salts except the nitrate 

 found in the water, boiled with some of the same sulphuric 

 acid, and tested by the same muriate of tin ; but in this case 

 no colour was afforded, nor any gold dissolved. 



The potash was ascertained to be present by evaporating a 

 quantity of the water until reduced to a small portion, filtering 

 it and then adding muriate of platina in solution. Three pints 

 of water, evaporated until about one ounce of fluid remained, 

 gave an abundant precipitate of the triple salt of potash and 

 platina. In cases where small quantities of the water were 

 tried, it was necessary to let the liquid stand an hour or two 

 after applying the muriate of platina, but the triple salt always 

 ultimately appeared. 



Two p'ints of the water, evaporated to dryness in a silver 

 crucible, gave, on re-solution of the residuum, a decided though 

 very minute trace of silica. 



THE LOGAN STONE IN CORNWALL OVERTURNED. 



To the Editors of the Philosophical Magazine and Journal. 

 Gentlemen, 



Your geological readers will hear with infinite regret that 

 the celebrated Logan Stone in Cornwall, which has for so long 

 a period been regarded as an object of great national interest 

 and curiosity, and which has been visited by persons from the 



Vol.63. No. 312. April 1824. Rr remotest 



