1881 .] 
239 
[Merrill. 
two classes of specimens, especially if it be borne in mind that 
the diagnoses of the thin sections were made the other side of 
the ocean, away from the precise hand-specimens now deposited 
at the museum. 1 The paragonite schist which I examined, though 
full of staurolith crystals, certainly carried no “ large crystals of 
pale-blue disthene,” as announced in the report. But since large 
crystals of pale-blue disthene, especially when occurring in par- 
agonite schist, their favorite abode, are as unmistakable as the 
most familiar objects in life, I think that it would never occur to 
most men to quote a mention of their presence in a specimen of 
such a collection as being an error perpetrated by an eminent 
man simply because the precise specimen now exposed to view, 
• and which gives every evidence that the very next fragment of 
the same sort would be likely to be rich in disthene, happens to 
carry none. But then, quot homines , tot sententiae concerning 
such points. 
On page 285 it is said : “ The [ZirkeFs] so-called hornblende 
porphyries are somewhat altered andesites.” Since there are 
only two specimens mentioned in the report as hornblende por- 
phyries and since Mr. Wadsworth names them both altered ande- 
sites, we have here the elsewhere vainly coveted knowledge of the 
precise specimens in question. But just here a difficulty occurs 
as to what Mr. Wadsworth really means — a puzzle which, after 
many readings, I have been unable to solve. The use of the 
terms “ old ” and “ altered ” in his paper seems quite ambiguous. 
Thus, Mr. Wadsworth proceeds: “. . . . and the diabases 
[of ZirkeFs report] are mainly altered basalts, but a few are 
report, this explanation seemed inadmissible. Moreover, I learned that Professor Zir- 
kel’s original manuscript, which contained the proper numbers corresponding to those 
on both thin sections and hand-specimens, was put at Mr. Wadsworth’s disposal as it 
was at mine. I may say, in this connection, that while I cannot understand Mr. Wads- 
worth’s results, my own microscopic examination did not lead me, in some cases, fully 
to concur with Professor Zirkel’s descriptions. But generally such differences concerned 
quite unessential points. In a few cases it was evident that confusion of specimens 
had occurred, and that the slide or specimen which I was examining was not the one 
described by Zirkel. In a collection of such magnitude, studied and reported upon 
under the circumstances which prevailed in this case, the rarity of such instances of 
confusion was matter for surprise to me. 
1 1 have been informed that such was the case; I presume, correctly. 
