192 Answers to Queries. 
scope, but the microscope has to be inclined. The one I have 
has been in use over 4 years, and only cost me 3/6. I find it 
quite as good as a more elaborate one. Beale’s neutral tint 
reflector is a cheap, useful piece of apparatus (5/-). I do not 
think that it makes very much difference which position the 
camera lucida is used in. The ones most common in use are 
horizontal. Chevalier’s is a good instrument, as are Zeiss’ and 
Nachet’s. One thing must be remembered. They are in many 
cases more useful for giving the actual size of an object as seen 
with a certain combination of lenses, and for giving the general 
outline of a section than for the individual details. (See Scéentific 
Enquirer, Vol. I., 1886, p. 68.) V. Ava: 
397.—Camera Lucida —The cheapest form of camera lucida I 
know of, and which I have used a good deal, is Dr. Beale’s 
neutrai-tint reflector. It ought to be made of a metal tube, with a 
piece of thin neutral-tint glass placed at the end at an angle of 
45°. It is very easy to use so long as there is not too strong a 
light on the paper, and costs 5s. to 6s. The objection to this and 
Wollaston’s camera is that the microscope must be put in a hori- 
zontal position before using them, thus altering the illumination. 
For this reason I prefer the vertical camera, as then the drawing- 
paper is placed parallel to the stage, and I have lately bought 
Abbé’s—(this costs, I think, two pounds)—and is a very good 
instrument. Zeiss, however, makes another form, price 21s., and 
Beck makes a vertical camera lucida, price 18s. 
The external diameter of Zeiss’ oculars is 23°3 mm. (‘917 
inch), and the Abbé camera is capable of adjustment within 
certain limits, so it might fit J. H.’s oculars; on the other hand, 
the mirror makes it rather heavy. J. G. P. VEREKER. 
398.—Animal Intelligence.—I would advise the enquirer to 
read Dr. Carl Semper’s “ Animals and their Conditions of Exist- 
ence” and Prof. G. J. Romane’s “ Animal Intelligence,” both of 
the International Scientific Series (Kegan Paul and Co.), and 
papers in Science Gossip. ‘Vi. ARM. 
399.—Dry Mounting.—For a quick and simple method, see 
Journal of Microscopy and Natural Science, Vol. IV., p. 27. 1 
prefer to use a metal cell, to be careful to have dry objects, and 
use very, very little gum on any specimen which is not large 
enough to fill the cell, and having got rid of the moisture from 
the gum, etc., seal up the cell. Two plans may be used to close 
the slide. One is to cut a groove in the metal cell to allow of the 
escape of vapour, and then stop up the orifice at some later 
period. The other is to have the cover-glass so small that it will 
only just rest on the inside edge of the cell, and allow all but a 
very small portion of the cement to be exposed for evaporation. 
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