MICROSCOPY. 241 
scopic with any objective, from a four-inch to a y, inch; and of 
course it may be used for dissecting by transmitted or reflected 
light with any objective having ‘‘ working distance” enough for 
manipulation — certainly with a half-inch. The only objection, if 
it is one, against the instrument for this use, is that the “ power,” 
the amplification, is necessarily higher than with other binoculars. 
But where a very low power is wanted I believe a pair of specta- 
cles set with magnifying periscopic lenses will prove to be better 
than any binocular dissecting microscope yet devised. But the 
objection to the “usual erector” for monocular instruments re- 
mains. This was remedied by Tolles years ago; so long ago that 
he has forgotten when. He made erectors that did not disturb 
any of the corrections of the objective, but preserved them and 
gave as good effects as were obtained without an erector. 
When will American microscopists learn what has been done in 
instruments made in their own country, by their own artists? 
S. 
as ae ee E ETT Le a ee ee E EA oe NEE ee 
Nore on toe Apove Remarks. —It can hardly be necessary 
to state that Tolles’ binocular eye-piece, with which the writer has 
Sometimes worked, was ignored in the paper referred to, simply 
because there was no occasion to mention it,— it being no novelty 
but an article whose properties, have been perfectly familiar to 
American (and foreign) microscopists for years. It is only fair 
` to add that the new arrangement, which can be added to any 
Microscope at a cost of two or three dollars, has been used for 
months by several microscopists who consider it extremely simple 
and convenient. 
that an erector (or anything else) however perfect, can be 
added to the objective and ocular and give “as good” optical 
effects as would be obtained without the additional refracting and 
dispersing surfaces, is much disputed and surely cannot be 
considered a conceded point at the present time. 
If Mr. Tolles is prepared to supply the market with erectors 
radically superior to those generally used, microscopists will doubt- 
ie learn the fact when it is announced, as I do not find it now, 
in the Catalogue of the Boston Optical Works or in their adver- 
tisements in the Narvuratisr and other journals.— R. H. W. 
KSA 
_ Osuique ILLUMINATION.— A new contrivance, for obtaining 
e transparent illumination with high powers and black 
AMER. NATURALIST, VOL. VI. 16 
