I54 Answers to Queries. 
its focus) from 4 to 5 times and from 8 to 10 times—that is to say, 
an inch ought to give from 40 to 50 diameters with one and 80 to 
roo with the other. There ought to be means of applying a 
polariscope, spot-lens, substage-condenser under the stage, and 
the focussing ought to allow of the use of at least a 2-inch power, 
if not a 3-inch. A case is a luxury, as microscopes are kept most 
conveniently under bell-glasses. The following are the most 
generally useful magnifications, put in the order of their import- 
ance: 40 t0 50; 200 to 30087m5 to 25 5 400 to Goomseiibese 
numbers are, of course, only approximate, and are given in dia- 
meters. High powers are much improved by the use of a 
substage-condenser. For general work, the most useful substage 
appliances run in the following order :—Diaphragm, spot-lens or 
paraboloid, polariscope, and condenser. If a substage-condenser 
with stops are got, the spot-lens can be dispensed with, any way at 
first. The smallest number of things to begin work with is a 
stand with draw-tube, fine motion and eye-piece, a stand or stage- 
condenser for opaque objects, and a suitable power for the work 
undertaken—say, an inch or #-inch ; to this the next to be added 
is a { or } inch, and then a second eye-piece. After this expe- 
rience will teach the rest. Ninety degrees is quite high enough an 
angle for the 4+ inch, as otherwise it will work too close to the 
object. Always get good objectives from well-known makers. 
The most popular foreign objectives are those of Zeiss’. The 
cheapest form of camera-lucida for drawing is Beale’s reflector, 
but I prefer the vertical camera. In this case the paper is put 
parallel with the stage. One caution: do not be tempted to buy 
separating objectives, and remember that English objectives, as a 
rule, work best on 8- to 1o-inch tubes and foreign ones on the 
6-inch tube. I send the addresses of those mentioned in this 
reply, but there are other excellent makers. The two best-known 
firms are—Powell and Lealand, 170 Euston Road, N.W.; Ross 
and Co., 112 New Bond Street, W. Beck and Co., 68 Cornhill, 
make very good instruments, and the cheapest I know of is the 
“Star.” Baker and Co., 244 High Holborn, agents for Zeiss and 
Siebert, also second-hand lenses, etc. J. Coppock, New Bond 
St., agent for Hartnack, Nachet, and American makers (Tolles, 
etc.). C. Collins, 157 Gt. Portland St., also sells second-hand 
lenses and instruments. 
In getting a microscope, do not buy too much at once, or you 
may get appliances you do not want ; also, get some good work on 
the subject before purchasing. John Phin’s ‘‘ Howto Use the 
Microscope ” (3/6, ?), Davis’s “ Practical Microscopy” (7/6), Car- 
penter, ‘‘ Microscope,” would all suit R. C. 
J. G. P. VEREKER. 
