82 On the Localities of certain ReUcjuia, or 



extraneous fossils are propLrly, that is, scientifically* d'is- 

 crimiiiated, has lotiir been my own opinion ; and this opi- 

 nion hns been abundantly confirmed by a conversation I 

 have lately had with your most ingenious correspondent 

 Mr. J. Farcy, whose knowledge of the stratillcation of this 

 island is unquestionably great. This gentleman has well 

 pointed out to me tlie utility as well as the practicability 

 of distinguishing the various strata in a soil, or series of 

 strata) by their organic contents. And I regret, that in the 

 first volume cf the publication above mentioned I have not 

 paid more particular attention to this point ; that is, not 

 only by noting the immediate siralum (whenever I have 

 ascertained it), in which the species has occurred, but alsQ 

 the particular situations {Ivca .specialia) where it is to be 

 found ; as these in many instances would give others an 

 opportunity of determining the immediate, where I have 

 only been able to speak as to the general soil. In the se- 

 cond volume of the work in question, which 1 am now 

 prep?.ring for the press, it will be my aim to give the geo- 

 logical as well as the geographical situation with more pre- 

 cision. The following additional remarks to the localities, 

 enumerated in my first volume, may not only be useful to 

 the purchasers of the work, but also induce geologists to 

 pay some attention to a subject, that has been hitherto so 

 iiiuch neglected. 1 am, sir, your obedient servant, 



William MARTiN.f 



* I hope that geologists will not in future be content merely to say, 

 that such a rock " abounds in Bciemni-tes, Terebrntuh, Echinites, &c." 

 or tliat such a formation of sti-ata " contains Ammonites, &c." Such in- 

 forniatiou can be of little use, unless the species are well characterized. 

 This, in manv instances at least, may be done with accuracy ; and it is 

 evident, that almost every practical inference that is to be deduced from 

 a knowledge of r^liqucs, will depend in a great measure on their being 

 specificnlltf distinguished. 



f [On an application to Mr. Farey, and a reference to his Correspondence 

 with tlie able ai-.d lamcntL-d Author of this I^etter, it appears, t'uit the draft 

 of it was prepared between the 17th of July and the 7th of Augiisc 1809, 

 although only part of the first page seems to have been transcribed by Mr. 

 M. in the copy lately sent to me by his Frrends; which suspension and delay. 

 seem to have originated in the wish that Mr. M. hud, first to avail himself 

 of the information to be derived from the manuscript Mineral Map and 

 Section of Mr. Farcy's, since mentioned in the No:e p. xxi. of the Pre- 

 face to Mr. F.'.s Dcrb\ hire Report, vol. i. and on \\hich account also, he 

 countermanded a Seclion that had been engraven (before he knew Air. F.^ 

 and suspended his olher proceedings with respect to the promised Suyu/j/e- 

 meiit to the 1st vol. of '' I'elrificata Derbicnsia," (as appeur* by his Letters 

 to ATr. /.), hut unfortunately, lie did not continue in health or live to re- 

 ceive the \hip and Section ailud;.'d to. I have thought these particulars 

 might be worth stating rrspecling this worthy man, in addition to the ^V/i?- 

 mnirs of him in the " Monthly M igazinc" for January last, vol. xxxii. p. 556. 

 \ have availed myself of Mr. Farey's Assistance in three or four corrections 

 or suggestions (in parenthesis) as to the identity of particular strata; and I 

 gladly embrace this opportunitvf\irtlier to mention, that Messrs. White and 

 Cochrane-, in Fleet-Street, who continue lo sell Mr. Wm. Martiu's two wnrk<^ 

 'lu extraneous Fosiils for the boucut of liis Widow (in a poor stale of heaUlij 



