WIDE DISTRIBUTION OF ALLANITE. 307 



without changing its physical character was evidenced as a strong proof 

 against the igneous origin of granite. This objection was met by 

 Scheerer* as early as 1842, in a paper entitled " Erste Fortsetzung der 

 Untersuchungen iiber Gadolinit, Allanit, und damit verwandte Mine- 

 ralien," read at Stockholm before the Society of Scandinavian Naturalists. 

 Some years later the same writer f discussed an aqua-igneous theory of 

 the origin of granite, and suggested that owing to the presence of water 

 the magma may cool down considerably below the temperature neces- 

 sary for solidification under the conditions of ordinary dry fusion, and 

 thus allow minerals which cannot endure great heat to crystallize out 

 before other constituents more difficult to fuse by the simple dry method. 

 Both Elie de Beaumont and Daubree and later others have confirmed 

 this theory experimentally. 



Since Scheerer's time a number of writers have noted the occurrence 

 of allanite in various igneous rocks. Chief among these allusions may 

 be mentioned those of Blomstrand,'| von Fritsch,§ Vom Rath . j | Liebisch* 

 Tornebohm,** Iddings and Cross, ft Michel-Levy and Lacroix, H 

 Hobbs, §§ and Lacroix. || 



In Maryland, Hobbs appears to have been the first to call attention to 

 the presence of allanite in the rock of the state. The specimens espe- 

 cially studied were from certain granites and porphyritic granite from 

 the immediate vicinity of Ilchester. Since the announcement of these 

 occurrences similar allanitesand allanite-epidote intergrowths have been 

 found at other places — at Dorseys Run station, and in less abundance 

 at Woodstock, and on the Gunpowder river, northeast of Baltimore. 

 Since the appearance of the first note on the allanite-epidote intergrowths 

 from the porphyritic granite of the Ilchester district some doubts have 

 been raised as to whether the exterior clear portions of the grains are not 

 in reality the same mineral as the interior dark parts, but differing 

 slightly chemically. For this reason the author ^]~*| just referred to reex- 

 amined some of his earlier preparations and after the complete isolation 

 of the dark central allanite had a chemical analysis made of some of the 



*PoggendorfFs Annalen der Phy. u. Chemie, lvi Band., 1842, p. 479. 



fBuI. Soc geol. de France, 2d ser., tome i\\ 1847, p. 468. 



JOefvers. af akad. Forhandl., no. 9, 1854, p. 290. 



< Zeitsch. d. d. geol. Ges., xii Band., 1800, p. 105. 



I] Zeitsch. d. d. geol. Ges., xvi Band., 1SC4, p. 255. 



1 Zeitsch. d. d. geol. Ges., xxix Band., 1877, p. 725. 



**Geol. Foren i Stockholm.Forh., vi Band., 1882, p. ls:, : also, Vega Exped., vol. iv, Stockholm, 

 1884, p. 115. 



ft Am. Jour. Sci., 3d ser., vol. xxx. 1885, p. 108. 



JJBul. Soe. min. de France, tome xi, 1888, p. 05. 



H Johns Hopkins University Circulars, no. 05, 1888, p. 70; also, Am.. Jour. Sci., 3d ser.. vol. xxxviii, 

 1889, p. 223. 



Illl Bui. Soc. min. de France, tome xii, 1889, p. 139. 



1ft[ Am. Jour. Sci.. 3d ser., vol. xxxviii, 1889, pp. 223-228. 



XLVI— Bull. Geoi,. Soc. Am., Vot,. 4, 1892. 



