; 4 Monthly Mi ical 
280 American Microscopes _ [Sotmal, Nov. 1, 1870. 
in this paper, as he should have done) that because he did not count 
all the lines at once, they were not resolved ; and it is true that 
he is not alone in that theory. To show the absurdity of this 
we will suppose that Nobert had ruled in the 19th band only 
28 lines instead of 57, would Dr. Hagen say they were not resolved, 
when he saw the whole, because there were no more? Or if Nobert 
had covered a whole inch with the 112,000 and some odd lines, 
would anyone claim that they must all be seen at once? If either 
of these suggestions is answered in the negative, then Dr. Hagen 
has himself seen the 19th band resolved with a Tolles’ objective. 
But Dr. Hagen says that American objectives have done “never 
more than European,” and yet what he did with a y5th objective is 
much “ more” than to see all the lines with a ygth (really a oth). 
He never saw, read of, heard of a yoth European objective that 
would do what that one accomplished. This is not all; his sight of 
the Surirella gemma gives the same contradiction to his “opinion.” 
He says, “ S. gemma with the same jth showed only in a few 
places oblong fields between the cross-lines, but not well defined or 
recular as in Hartnack’s drawings.” Well, did anyone ever see 
them so? If Dr. Hagen knew as much of diatoms as of insects, he 
would have been aware of the fact that Hartnack’s figure is a theo- 
retical diagram, not a representation of the appearance in the 
microscope. Probably the only person living who claims to have 
seen what Hartnack calls the “ flat hexagons,” is Mr. Bicknell, 
who says he saw them, and only with a Tolles ;5th. Hartnack 
does not say distinctly that he has seen them with a 7th; he 
attempted to show them to two accomplished microscopists, and 
both failed to see them.. Dr. Eulenstein has also failed with Hart- 
nack’s Nos. 10, 11, and 12, Powell and Lealand’s oth and Ross’ 
objectives; and Dr. Hagen knew these facts, for the writer told him 
before his paper was written ; comment is unnecessary. Dr. Hagen 
also says that Hartnack’s y,th has resolved S. gemma, and Tolles’ 
joth has not, ergo Hartnack’s has done what 'Tolles’ could not. 
Dr. Hagen has himself furnished the “ direct proof” he wanted of 
the “ unsurpassed excellence ” of the American objective. 
Now for some of Dr. Hagen’s errors and mistakes. He says of 
Tolles’ objectives “the workmanship is’ superb,” “the adjustment, 
only moves the lower lens from the two others.” The solid eye- 
‘ 
pieces are “really bi-convex Coddington lenses.” He gives on the | 
authority of Edwards a formula of Tolles’ objectives; all there is to 
be said is, that the formula is not Tolles’ formula, the eye-pieces 
are not Coddington lenses, and that Tolles had never made objectives 
to move the front lens; all of which Dr. Hagen could have easily 
ascertained. : 
Dr. Hagen considers that “a most important fault of the instru- 
ment consists in the difficulty of its use. In order to adjust them 
ora «er cee ie eh 
