1881.] 
273 
[Wadsworth. 
In the case of the chemical analyses, part have been made from 
rocks not described by Zirkel ; and the same difficulty, as mentioned 
above, occurs even in greater force in tracing the analyses to 
the descriptions given in Volumes I, II, and III, and when they 
exist, in V ol. VI. In some cases the writer has been unable to find 
any account of the rock analyzed, beyond the simple analysis. 
In other cases the specimens analyzed came from outside of the 
district ; while in some cases it was found that the analyses given 
in Vol. I differ in some of their percentages from the analyses 
in Volume II, although they purport to be the same analyses. 
No explanation of this has been found in the reports, and 
although the differences are not great they must, until explained, 
throw some doubt on the accuracy of the work, especially since 
the changes tend to bring them more in accordance with the 
theory. 
In fact, it would seem difficult to throw more obstacles in 
the way of getting at the facts which underlie the theories than 
has been done in the reports and with the collection of the For- 
tieth Parallel Exploration. Each volume by itself appears com- 
plete ; to connect them and to trace the facts and theories from 
one volume through the others and to the specimens themselves 
is the difficulty. 
In some cases either the slides or specimens or both were mis- 
sing. Attention was called by me by writing upon the labels, to 
certain errors in slides and to the misplacement of the hand 
specimens. One of the curious mistakes observed may be pointed 
out here, as it will illustrate the difficulties one labors under in 
studying the collection. There are two slides numbered 2772 
(No. 55, Vol. VI, p. 35). One of these belongs to Col. No. 2777, 
and is the slide described by Zirkel (No. 55). The second section 
2772 was taken from specimen Col. No. 2773, and is described by 
Zirkel as No. Ill, Col. No. 2775 (VI, p. 56). Now specimen Col. 
No. 2772 belongs in reality with slide 2773. Such was the state 
of these slides and specimens in 1878, and is only one out of 
many such cases, generally less complicated, that the writer had 
to trace out. In no case, when they could be accounted for in 
the above manner, have any of the errors been placed to Profes- 
sor Zirkel’s account. The statements as to the cyanite, that a 
VROCEEDINGS B. S. N. H. VOL. XXI. 18 MARCH, 1882. 
