4a8 Memoir on the Foffll Cmut-Chouc, 



One of the precipices of this mountain is kno*n by the 

 name of Hay Cliff: it is calcareous, and contains fhells and 

 other marine productions in a ftate of petrification. The 

 other is called Man-Tor: it is alfo calcareous, and towards 

 the foot there are iome galleries of a mine, on a vein which 

 terminates near the furface, and of which the matrix is a 

 milky calcareous fpav containing large-grained galena, but in 

 fmall quantity. Thepe are found alio towards the bottom of 

 the i'ame precipice, as well as in fome other parts, fiffile ftrata 

 of argillaceous fchift, very often marlv, which imbibe water 

 in the time of rain, fplit, and occafion the folid and ftony 

 mafl'es which rell above them to crumble down*. 



Some of the fchillous ftrata in queftion have a certain 

 hardnefs ; but all in general have a character of alluvion which 

 an experienced eye cannot miftake, and yet their formation is 

 of the higheft antiquity. It is at a depth which, without fear 

 of being deceived, may be ertimated at lead at four hundred 

 and fifty feet below the upper llralum, that the foffil caout- 

 chouc has been found, and particularly the large fragment 

 in the polfeflion of Mr. Mawe. In general it is in fmall ca^ 

 vities, in a kind of neils between the fiffile ftrata, that this bi- 

 tuminous matter is contained ; and as in this (late it is fhel- 

 tered from the action of the air, it needs excite no furprife 

 that it tliould have experienced only very little alteration, and 

 that its nature is not changed. 



In the lait place, one of the cavities, twenty-two inches in 

 length and five inches in height, contained a great deal of 

 caout-chouc. By thefe means verv fine fpecimens of it may 

 be obtained for colleftions, at a very inoderate price; and it 

 is to Mr. Mawe that we are indebted for this obligation. 

 This gentleman, who with his father-in-law Mr. Brawn pof- 

 felTes a large raanufa6lory of fparry fluor, of which they make 

 elegant vafes and other ornaments, carries on trade in a very 

 honourable manner with the minerals of Scotland, Derby- 

 {hire and other parts of England, a depot of which he pro- 

 pofes to eftablifli at Paris, whicli mult, no doubt, be of ad«. 

 vantage to the progrefs of mineralogy. 



I divide the foffil caout-chouc of Derbvfhire iiito elaftic or 

 compreffible bitumen, and folid, hard, and brittle bitumen, 



♦ <' The earth and ftoncs which cramble ilown from this mountain," 

 fays Ferber, wtio vifucd thelc places levunil years bctorc J did, " form in 

 feveral places fmaii hills, the fiz.c- of which daily increales, and which tire 

 people cQnlidcr as one of the fevun wonders of the Peak."— £^«' dOiyc- 

 lograpbic du HcjbyJbirCt par Ferbcr, 1'tmI. F)ancoiJe, p. zi. 



' SfiCTIOlrf 



