156 Dr Henry on the Magiiesite of Anglesey, 



you thought that this new locahty deserved to be the subject 

 of a notice in one of the scientific journals ; and I send, there- 

 fore, the following short account of it for insertion in that 

 with which you are associated : — 



At a short distance from the Parys mountain (I believe 

 S. W. and within a mile of it) there is a low hill composed of 

 green serpentine, which is probably similar in its character to 

 other hills of about the same elevation, which are seen to rise at 

 no great distance. The serpentine is traversed by narrow veins 

 filled with a mineral, which, on first view, struck me as resem- 

 bling the hydrate of magnesia discovered by yourself in Shetland. 

 It is of a greenish white colour ; a foliated structure ; translu- 

 cent at the edges ; rather soapy to the touch ; and soft enough 

 to yield, not easily however, to the nail. Its specific gravity 

 (twice taken) is 2.820. On chemical examination it was found 

 to differ essentially from the Shetland hydrate, which, accord- 

 ing to Dr Fyfe's analysis, is the proto-hydrate of magnesia. 

 The Anglesey mineral dissolves very slowly in pretty strong 

 muriatic acid, with an escape of carbonic acid gas, the volume 

 of which, from 100 grains, may be reckoned to be equivalent 

 to about 19 grains. The solution, however, is not complete, 

 even when assisted by heat ; from 54 to 60 parts remaining 

 undissolved, and when a small fragment has been used, it pre- 

 serves its general form. The dissolved part consisted almost 

 entirely of carbonate of magnesia and carbonate of lime, in the 

 proportion of about 28 of the former to 12 of the latter. Both 

 these carbonates must, in the mineral, be anhydrous ; for no 

 difference, that can be counted upon, is found between the loss 

 sustained by a white heat, and that effected by solution in acids. 



The insoluble portion I have not had time to analyze ; but 

 it appears to me very much to resemble common talc. This 

 may have contained cavities, which may have been afterwards 

 filled by an infiltration of magnesite. I throw this out, how- 

 ever.^ as a mere conjecture. 



It is probable, that, if the rock were opened out by blasting, 

 much finer specimens might be obtained than any I possess, 

 which are small and somewhat weathered. It is not unlikely, 

 also, that the chrome-oxide of iron would be found on the 

 same spot. 



