634 AMERICAN ASSOCIATION ADVANCEMENT OF SCIENCE. 
microscopes, et id omne genus, should latest and least feel the control of 
real science in their construction. Only a few years ago in London, and 
. much later in this country, was there any serious effort to make students’ 
microscopes worthy of the times. Even now some of the best of these 
are sold without a diaphragm below the stage, or with so small a body 
that the lowest (and, for beginners, best) eye-piece gives a ridiculously 
mall field, and too many are still built upon the old vertical plan which 
um been iin te for twenty years. In regard to stereoscopic micro- 
scopes the case is still worse. Tolles’ binocular eye-piece **for microscopes 
only ” is not yet in the market, though expected for years, and Wenham "8 
binocular, long since popularized in England, is nearly unknown here ex- 
cept on large and costly instruments. Grunow, of New York, has done 
something during past years to furnish small bi nocular instruments. 
When will he, and Tolles, and Zentmayer, and Miller, and McAllister, ^ 
others, do for us what Crouch, and Collins, and Murray and Heath, 
Beck, and many others, have long since done for England in Fares an 
abundant variety of good binoculars of moderate size and cost? If the 
binocular microscope were unnecessary for anybody it would be for the 
diatomist; yet I can scarcely believe that such a person, after s So 
Móller's ipa plate a illuminated under a 4-10 objective of Mans 
120° in a good binocular, would ever advise any person to purchase a 
monocular instrument except as a necessity of price. While we are 
waiting ro still further a nts in the binocular, promise of whic 
ma Mr. Holmes' bisected lens, the erecting binocular of Mr. 
Stephenson, and the binocular by double ee of Dr. Barnard, let 
t on 
s 
croscopical work, the Eq the ie cd , s, and the light, the e is 
be still better; and probably Tolles’ orthoscopic eye-piece would answer ~ 
the same purpose. e illuminating angle would be varied by focussing 
below the object, with much less logs pa definition ae in the old style 
of using an objective for the same purpose; or, preferably, various stops 
of blackened card would be oe below th sese lens to stop off any 
desire 
used to correct the yellow glare of preside Hue. Rebbe slight mechan- 
ical ingenuity the student can combine th diaphragm 
of blackened card or brass, and sonaat josreane the convenience of 
