HEVIKW OF PKKVrors STCDIKS OF I)0LO>rrTFS. 180 



series;, and ])artii'ularly tlie Saint I.awrenco, witli its varicMl litlu)l()<;ic 

 cliaracters and wide distriluition. 



rilE DOLOMITES. 



Historic Outline. — TiOng before clieniical and i)liysical facts were known 

 or geology luid l)ec(nne a science, dolomites received considerable atten- 

 tion. In 1779 Arduint) liad traversed tbe carl)onates aronnd T.avina and 

 readied tbe conviction tbat tliis de})osit of carbonate of lime and mag- 

 nesia was formed from calcium carbonate through the operation of 

 igneous agencies originating in the depths of the earth /'^ 



In 17i)2 de Saussuref recognized dolomite as a distinct rock s[)ecies in- 

 stead of a peculiar modification of limestone through metamorphism 

 and gave to the species the name dolomite, in honor of his contemporary, 

 Dolomieu, who had already noted some of its most prominent characters. 

 Heim.J in his geologic description of the mountains of Thuringia, appar- 

 ently independently reached nearly the same conclusion touching the 

 alteration of the limestones as had Arduino a generation before him. 



Leopold von Biich,in a series of interesting letters § written mostly in 

 1822, described many of the phenomena of bedding and relationships in 

 the dolomites of Frankenland, various portions of Tyrol, and the neigh- 

 borhood of the Eifel volcanics. These letters are a most valuable con- 

 tribution to the geologic literature of the first half of the century, and 

 really laid the foundation to our knowledge of the dolomitic rocks. 



In 1841 Studer, in a letter to the editor of Xeues Jahrljuch,|| })ropoun(l3 

 the (juestion whether dolomites ma}" not be the product of isomerous 

 carbonates being deposited together, the resultant taking the place of the 

 calcium carbonate removed. Then Petzholdt examined for himself the 

 dolomites of the Tyrol district ^[ and concluded that the view accepted 

 by some of bitterspar pseudomorphosis was insufficient, l)ut noted in a 

 series of specimens taken from the successive layers that those re])re- 

 senting the uppermost contained the most magnesium carl)onate; in- 

 deed nearly the proportion for normal dolomite was reached in them, 

 while the lowest layers were nearh^ pure calcium carbonate. A. v. Morlot 

 recounted an interesting series of experiments to discover a chemical 

 basis for a theory of the origin of dolomites.*'^ The idea of a purely 

 chemical origin should probably be expected at this stage ; certainly we 

 are not (lisapp«jinted in finding it. Two years later Favre ft discussed an 



*Ck)mpare Naumann Lehrbuch tier GeoKnosie, Leipzig, second edition, vol. i, p. 7G4. 

 fNeiies Jftlirbufh ffir Mineraloeie, 1847, p. 862. Auszur. 



Jfieol. BoM<;lir. dos Thuringer Wjildgebirges, Theil ii, Ahtii. 5, 18(»r,, pp. 99-111 ; also, Nftumanii 

 (ifoenoHie, cited, p. 7»>4. 

 : NI M.-rulogiMchoH Laflchcnbticii fur diis Jalir, 1824, pp. 239-.*0fi. 



N- ii.H Jalirbiich ffir Mincralogie, 1844, pp. 18.V189. 

 \ Vvhvr Dolomit-bildunK. Neues Jahrbuoli fur Mincrulogic, 184*., p. 72--', Auszu^. 

 ••Neuoj* Jahrbuch fOr MIncralogle, 1847, p. 802. 

 tfNeues Jahrbuch, 184'J, p. 742. AuHZUg from Comptes Rcndus, 1819, vol. xxviii, pp. 304-3f',c.. 



