542 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
A New Construction for the Microscope.* — Dr. Hugo Schroeder, in 
reference to the paper by Dr. Lendl in Zeitschr. f. Wiss. Mikr., viii. 
(1891) p. 281, of which an abstract appeared in the last number of this 
Journal, has anticipated many microscopists in pointing out the fallacy 
involved in the conception that any real increase in the capacity of the 
Microscope is obtained by replacing the eye-piece of a Microscope by a 
second auxiliary Microscope. He also shows that the idea of such a 
construction has not even the merit of being new. A similar construc- 
tion was originally described by Prof. Listing in Carl’s Repertorium, v. 
(1869) pp. 1-5, and 134-40, and an extension of the same idea was made 
by Prof. Piotrowskiego,j' who used Hartnack lenses partly with negative 
foci, and went even farther than Dr. Lendl with his (empty) magnifica- 
tions. 
Errors of this description were possible at a time when the diffrac- 
tion theory was not generally known, but they are inexcusable now when 
the work of Prof. Abbe should be familiar to every microscopist. Such 
an arrangement as that proposed by Dr. Lendl only serves to magnify 
the structures in the Microscope image which have been altered by 
diffraction, and does not tend to give a clearer definition of any detail 
than can be obtained by the use of good eye-pieces. The capacity of 
the Microscope is not to be increased by any such simple method as this. 
For such a purpose processes, such as the increase of the numerical 
aperture, which aim at the diminution and prevention of the errors of 
diffraction are the only means which can give any profitable result. 
An All-around Microscope.^ — Prof. S. A. Forbes writes: — “My 
personal studies are of a kind to require a Microscope which may be 
used (1) for the study of bacteria slides, (2) for the study of mounted 
slides of serial sections, (3) to search through and examine carefully 
collections of minute alcoholics in glass dishes, (4) to dissect animals 
under powers varying from twenty to two hundred diameters, and (5) 
to study pinned insects in all positions. 
For the first purpose one must have a stand fitted to carry 
objectives of the highest power and the best illuminating apparatus ; 
for the second, something in the nature of a mechanical stage is very 
desirable, but this must have a far wider sweep than the ordinary 
geared stage ; for the third, one must be able to explore rapidly and 
with low power a large surface, moving back and forth along parallel 
lines as with a mechanical stage, but with much freer motion in all 
directions. The stage must also be without surface projections or 
attachments which would be in the way of a glass dish of consider- 
able size. 
The instrument must, further, stand erect, and yet must not be 
too high to w r ork at sitting. It is a great advantage if both eyes 
may be used. 
Fourth, for dissection hand-rests must be provided, and the Micro- 
scope must usually stand erect, and should be a binocular. Fifth, 
for entomological work a binocular is needed, with stage socket for 
insect forceps, and with a large central opening in the stage to allow 
* Central-Ztg. f. Optik u. Mechanik., xiii. (1892) p. 98. 
t “ O Mikroskopach I Teleskopach” in Osobne od bioie, z. xxxix. Tomu Boczu 
Tow. nauk. krak. X Amer. Mon. Micr. Journ., xiii. (1892) pp. 91-2. 
