88 THE MIcROSCOPE. 
produce the very best objectives possible, largely from personal 
pride to excel rather than to fill any pressing wants of American 
investigators. It is certainly unaccountable when it is an indis- 
putable fact that in order to have defining and resolving power 
we must have the best glasses; and that resolving power and 
angular aperture go hand in hand. The German government, 
realizing the above, appropriated some time ago twenty-five 
thousand marks to enable Dr. Carl Zeiss to make experiments 
in the manufacture of new glasses suitable for lenses. It is 
most gratifying to learn that Dr. Zeiss has succeeded beyond 
expectation. Dr. H. VanHeurck, of Antwerp, reports as fol- 
lows on a new homogeneous immersion one-eighth, with a nu- 
merical aperture of 1.4: “It has greater resolving power than 
any we have had hitherto. Amphipleura argenteum is resolved 
into pearls over the whole surface, and with such sharpness that 
they may be counted. Bacteria will probably exhibit details of 
structure as yet unknown.” Thus the report continues. We 
trust it will not be long before some of our readers will be able 
to announce himself the possessor of one of these new glasses. 
This issue is nearly a week late. A quantity of proof lost 
through the mails, and not yet recovered, accounts for it. 
" For Ormentine Brass Cgtis to Guass Suipes.—Ist. Oar- 
bonate of lead, 4 0z.; red oxide of lead, 4o0z.; litharge, 14 oz. 
Grind thoroughly in a mortar. Stir some of this into enough 
gold size to make it work stiffly. If too much adheres to the 
work, turn it off on turntable when a little set. 2d. Best quality 
gum arabic, dissolve in cider vinegar; add a little sugar. A 
very strong cement, but have not tested it for durability—Me. 
Bulletin. 
I REMARK, en passant, that the mere resolution of a specially 
high band seems to have been erroneously regarded by Herr 
Nobert and others as a sufficient test of the quality of an objec- 
tive; whereas it can be demonstrated that the fact alone that 
an objective resolves a given band proves only that the particu- 
lar zone of aperture which is utilized in such resolution is free 
from aberration; and this may obtain in an objective in which 
nearly the whole of the other portion of the aperture is so 
affected by aberration that the objective, asa whole, must be 
regarded as of inferior quality. —J. Waydall, Jr. 
