1882.] 113 [Zirkel. 



6. Concerning the silvery-white mica-slate of the Red Creek, 

 Uinta Mts., upon which Mr. Wadsworth lays so much stress, the 

 gentlemen may rest assured that, when I examined the collection 

 in .New York, there was one specimen containing blue cyanite. 

 If, at the present time, this specimen is not to be found in the 

 collection, I am not responsible for its absence. What could pos- 

 sibly have been my object in quoting " excellent large crystals of 

 pale blue disthene " if they really were not present. Mr. Wads- 

 worth instead of arriving at this simple explanation of his own 

 accord, prefers to accuse me of error. 



7. Of course the geological classification of the granites came 

 primarily from Mr. King and his colleagues. Mr. Wadsworth 

 knows that sufficiently well, himself, and nevertheless he says> 

 that it was I who stated the eruptive nature of one granite, who 

 regarded another granite as Jurassic, etc. In the same manner 

 he accuses me of having erroneously stated that the augite 

 andesites are younger in age than the rbyolites (b. 265). 



8. Few will be likely to accept the odd doctrine of Mr. Wads- 

 worth, that rocks, in which the feldspars are nearly all triclinic, 

 should be called granites (b. 255), that orthoclase horneblende rocks 

 should be named andesites (b. 257). With a petrographer of 

 this stamp, who overthrows the most common and simple nomen- 

 clature familiar to every juvenile student, a scientific discussion 

 is out of the question. 



9. I have not stated, that the hornblende of the Fortieth Par- 

 allel diorites isin part an alteration product, but that it is (itself) 

 partly in a state of alteration — a distinction which Mr. Wads- 

 worth seems not to understand. 



10. Mr. Wadsworth is convinced that the true propylite is 

 an altered andesite. I may be permitted to ask, if he has ever 

 carefully traced the alteration of a real andesite, of such ande- 

 sites, for example, as those from the Siebengebirge or from Hun- 

 gary ; if he had done so, he would have seen, I think, that altered 

 and decomposed andesites never become propylites. Or has Mr. 

 Wadsworth ever observed an instance wherein the brown horne- 

 blende of a true (not of a " so-called ") fresh andesite alters into 

 a green hornblende and into abundant epidote, or wherein the 

 clear feldspars become laden with green hornblende dust, or 

 wherein this latter material is developed in the groundmass itself? 



PROCEEDINGS B. S. N. H. VOL. XXII. 8 MAY, 1883. 



