Curious Geological Fads. 457 



latter, tlie lustre resembles tliat of compactly crystallized lime- 

 stone, or marble. It either invests surfaces, or fills cavities in 

 chromate of iron. 



Its specific gravity has not been examined. It is soluble 

 boiling in the alkalies, and communicates to them a green colour, 

 but the solution is decomposed by further boiling, and the oxide 

 is precipitated. By this character, and by its communicating a 

 green tinge to glass, before the blow-pipe, it may be recognis'jtl 

 and distinguished. It occurs in Unst, one of the Shetland isles. 



Lest your readers should conceive that I had fallen into an 

 error, in describing this mineral as new, I ought to add to this 

 communication, that the oxide of chrome, described in Monsieur 

 Lucas's arrangement of minerals, is a very different substance, 

 and, I may add, improperly named. I need not quote from a 

 book which is in the hands of many mineralogists. It is sufficient 

 to remark, that his mineral is a compound substance, into which 

 the oxide in question enters only as an ingredient. It would be 

 proper that its name should be changed, to prevent confusion ; 

 the right of possession is clearly in the present substance. 



I am vours, &c. 

 Shetland, August 1820. '_ J. MacCuli.oCH. 



CURIOUS GHOLOGICAL FACTS. 



The following curious fact was stated in the Quarterly Re- 

 view, No. 43, p. 52, in an account of the quarries of marble 

 whence the blocks are taken for the construction of the Plymouth 

 break-water : 



" The quarries are situated at Oreston, on the eastern shore 

 of Catwater ; they lie under a surface of about twenty-five acres, 

 and were purchased from the Duke of Bedford for 10,000/. 

 They consist of one vast mass of compact close-grained marble, 

 many specuiicns of which are beautifuUv variegated; seams of 

 clay however are interposed through the rock, in which there are 

 also large cavities, some empty, ai/.d others partially filled with 

 clay. In one of these caverjis in the solid rock, fifteen feet wide, 

 forty-five feet long, and twelve feet deep, filled nearlv vvith com- 

 pact clay, were found imbedded fossil bones belonging to the 

 rhinoceros, l)cing portions of the skelctonrs of three different ani- 

 mals, all of them in the most perfect state of preservation, every 

 part of their surface entire to a degree which Sir Everard Home 

 says he had never observed in specimens of this kind before. The 

 part of the cavity in which these bones were found was seventy 

 iect Ijclow the surface of tiie solid rock, sixty feet horizont.ally 

 from the edge of the cliff where Mr. Wb.itljy l)cgan to work the 

 quarry, and one hundred and sixty feet from the original edge by 

 the side of the Catwater. Every side of the cave was solid rock : 

 the inside had no incrustation of stalactite, nor was there any ex- 



Vol. 57. No. 27fS. Jime 1H21. '3 M t'crnal 



