420 Expedition to the 



with any other rock. The extent of surface which it covers, 

 we believe, cannot be very great. This granite is very soft, 

 and disintegrates rapidly when exposed to the air. Grayish 

 white quartz, yellowish white feldspar, and an unusually 

 lar^e proportion of mica, in variously and brilliantly coloured 

 masses, enter into its composition. These large laminee of 

 mica are white, pearl coloured, yellow, brown, green, and 

 often black; and in some instances so large and numerous, as 

 to exceed in proportion the other ingredients of the aggre- 

 gate. Talc also enters in large proportion into the compo- 

 sition of this granite. It is indeed sometimes so abundant, 

 as to occasion a doubt whether the whole should not be con- 

 sidered a bed of ]talc, rather than granite. This talc is in ta- 

 bular masses, two or three inches in diameter, and about 

 half an inch in thickness. Zeolite is also so abundant as to 

 seem to take the place of the other materials of the granite. 

 It is of two varieties, radiated and mealy. Stilbite occurs in 

 connexion with zeolite. The bed of one of the small streams, 

 which traverses this formation of granite, is paved with 

 small crystals and beautiful tourmalines — that of another, 

 with native magnet. Sulphuret of iron is disseminated in the 

 granite. Several of the appearances presented by this inter- 

 esting mass of granite, would seem to countenance the opi- 

 nion that it is of secondary origin, like that mentioned by 

 Saussure, as existing near the valley of Valorsine, at Semur 

 in Auxois, and at the city of Lyons. In speaking of the gra- 

 nite at these places, he says, " It could not be doubted on 

 seeing these heaps of large crystals, that they are the pro- 

 duce of the rain waters, which, passing through the granite, 

 have dissolved and carried down these different elements, 

 and have deposited them in these wide crevices, where they 

 "have formed new rocks of the same kind. The crystals of 

 these new granites are larger than those of the ancient, on 

 account of the repose which the waters enjoyed in the inside 

 of these reservoirs." 



The granite of the Washita, if it is to be considered as of 

 secondary formation, appears to be much more extensive 

 than any of the kind hitherto known. Many more particu- 

 lars must however be ascertained, before this question can 

 be settled. We are ignorant of the manner of its connexion 

 with any other rock, nor do we know of any formation of 

 primitive granite, from which it could, by the action of wa- 

 ter, have been derived. One can have no hesitation, how- 

 ever, in considering the Ozark mountains a separate sys' 



