1883.] 42$ [Wadsworth. 



tiful trachyte " (303) and rhyolite (464) are nearly, if not quite, 

 identical. 



If Dr. Merrill's remark in his first paper (B. 236) be compared 

 with mine (W. 258) regarding the diabases Nos. 191, 192, 193, 

 194, and 195, which I consider as old andesites and which he takes 

 to be diabases (W. 461), it will be seen that we agree entirely as 

 to our determination, but differ merely as to names. It is to be 

 remembered, however, that Zirkel does not appear to use the term 

 diabase in the same way. Concerning the melaphyr, No. 209 (M. 

 461), it can be seen that my remark about the so-called augites 

 (W. 260) applies only to the forms which were surrounded " by a 

 very distinct series of blackish brown grains " and to the heaps of 

 grains. These characters are common to the andesitic hornblendes, 

 but not to the augites. Usually associated with these are augites 

 (or hypersthenes) having the planes given by Dr. Merrill, and such 

 is probably the case here, for such association is one of the char- 

 acters I rely upon in determining the old andesites ; but my notes 

 do not give the diagnostic points in this case, for I did not think 

 it necessary to take them down, supposing the collection would 

 always be accessible. The augite forms given by Dr. Merrill bear 

 out my view that this is an old andesite, for such well developed 

 forms are very common in the andesites, and very rare in the ba- 

 saltic rocks of America whether new or old, so far as my observa- 

 tion has extended. Of the quartz propylites of Zirkel it may be 

 said that Dr. Merrill agrees with me that No. 228 is a granite 

 porphyry in the Zirkelian sense, and that the quartz of No. 230 on 

 which Zirkel founded specific distinctions is an alteration product. 

 (M. 462.) 



In the case of No. 17 the quartzose material existed, as stated 

 by me ; but we may have had different sections, or we may differ 

 in our judgment as to what to call the material, or as to what is a 

 comparatively large amount, while even Dr. Merrill's description 

 of this section shows that Zirkel's work is imperfect and errone- 

 ous, if both had the same slide. (M. 462, 463 ; W. 265.) 



No. 386 Dr. Merrill states is of a light brownish tint on the 

 weathered surface and of a light grayish white color, glistening 

 all about with mica ; also that it has not the faintest shadow of a 

 resemblance to a basalt. Yet Mr. Wadsworth finds that the hand- 

 piece is " evidently a basalt." Not so fast. I said that a certain 



