30 
through which the upper part of the microscope tube projects about two 
inches, The space between the microscope and the box is closed by a funnel 
of light-tight cloth, the narrow end of which may be securely fastened round 
the microscope tube. The interior of the box is made dull-black by two or 
more coats of a black shellac varnish. The top of the box is constructed to 
hold the focussing screen and a reversible carrier for a whole plate dark slide, 
just in the same manner as in any ordinary camera. The dark slide contains 
adapters so that either half plates or quarter plates may be used ; in fact it 
is very rarely that a photograph larger than could be contained on a quarter 
plate is required, but the means of taking one of larger size is occasionally a 
great convenience. One of the main features of the camera lies in the door, 
whereby the operator’s head can with ease be inserted so that the object to 
be photographed may be viewed directly through the microscope, and the 
illumination, &c., of the object very much more conveniently and accurately 
performed than by the use of any other form of camera. The invariable 
distance of the focussing screen from the microscope adds considerably to 
the stability of the whole apparatus and renders it much more easy to obtain 
good photographs of minute detail. Only one focussing screen of moderate 
fineness is found to be needful. To render the focussing of very minute 
structures easy, blacklead lines are first ruled at regular distances apart on 
the ground surface of the screen, and then, here and there, micro. cover- 
glasses are cemented to the ground surface by Canada balsam. This entirely 
obliterates the grain of the glass, whilst the plane of the surface of the 
screen on which the image must be focussed is readily seen by the blacklead 
lines. 
DESCRIPTION OF ILLUSTRATIONS. 
Negatives taken on backed Ilford Chromatic Plates, and developed with 
Pyro-ammonia. Illumination in all cases axial. Condenser—Watson’s 
Achromatic of I'o N.A. Source of illumination, except where otherwise 
stated, Welsbach Incandescent Gas Light. 
Very much of the finer detail, shown in the original photographs, is 
unavoidably lost in the process of reproduction. 
Fig. 2.—Frustule of a Diatom. Navicula lyra, var. Watson’s 3}-inch 
oil immersion objective; no eyepiece; exposure 6 mins.; Oil 
Lamp Illumination. 
Fig. 3,—Dividing Nuclei (Karyokinetic figures), Microspores of Lilium 
auratum. Beck’s }-inch objective; no eyepiece; exposure 3 
mins. ; very narrow cone of light from condenser. 
Fig. 4.—Long: radial section of Pine-wood, showing bordered pits. 
Watson’s I-inch objective ; no eyepiece ; exposure 45 secs. 
fig. 5.—Trans : section of Pine-wood. Watson’s 2-inch objective; no 
eyepiece ; exposure 12 secs. 
Fig. 6.—Trans : section of portion of leaf-stalk of Palm. Watson’s 2-inch 
objective ; no eyepiece ; exposure I0 secs. 
Fig. 7.—Portions of Frustules of Diatom. Pleurosigma angulatum shewing 
both ‘‘ White dot” and “Black dot” appearance. Watson’s 
zz-inch oil immersion objective; A. eyepiece; Limelight illu- 
mination ; exposure 45 secs. 
Bitz © O ies 
