442 
POPULAR SCIENCE REVIEW. 
article constitutes its only disadvantage. MM. Davanne and Girard 
have more recently confirmed the favourable opinion expi-essed by Sir. 
Spiller. 
A very ingeniously-constructed microscopic camera has recently been 
introduced by Mr. A. F. Eden, of Crown-court, Threadneedle-street. It 
is made to serve a variety of purposes, and can be used either for taking 
reduced copies of photographic pictures or direct miniature portraits from 
nature, to be examined afterwards by the aid of an ordinary microscope ; 
or may be employed inversely for the production of magnified representa- 
tions of microscopic objects. The instrument may be described as con- 
sisting of a photographic camera adapted to the body or tube of an ordinary 
microscope ; and, although the combination serves the purposes already 
enumerated, the two portions may be disconnected, and each used 
separately. Thus, to the mahogany camera may be adapted a landscape 
lens of about sixteen inches focus, when it becomes suitable for copying 
and for taking small views on plates of sizes up to seven inches square ; 
likewise the optical portion of the instrument may be mounted on a brass 
stand, and requires merely an eye-piece to constitute an effective compound 
microscope. The manner of using the instrument may be briefly described. 
Supposing it be required for taking a micro-photograph, or reduction from 
an ordinary negative, the latter is supported in the position usually occu- 
pied by the ground-glass, or dark side in a camera of the usual construc- 
tion. This end of the instrument is provided with a large plane reflector 
attached by a hinge, and capable of adjustment to any angle which may 
be required to direct the rays of the sun or diffused daylight through the 
negative and axis of the camera. By means of the microscope object- 
glass in front of the camera, a sharply-defined image is depicted upon the 
screen of a little dark box placed a short distance beyond. The lens may 
be adjusted and focussed by the aid of a rack work and pinion movement ; 
and when the optical perfection of the image is deemed satisfactory, the 
scratched glass is exchanged for the sensitized plate, in this instance repre- 
sented by a single drop of collodion upon a slide of standard dimensions — 
one by three inches. The exposure will not usually exceed ten seconds in 
bright daylight, and the development occupies but a single moment, since 
it is advisable to guard against too great intensity in the minute photographic 
reproduction, in order that the speck of reduced silver on the glass may 
exhibit under assisted vision its proper gradation of light and shade. The 
beauty of the result, and the rapidity with which the whole process is 
executed, will possess a charm for those whose leisure moments are scarce, 
and whose laboratory facilities are of a limited character. On the other hand, 
by placing in the little dark box a microscopic object mounted on a glass slide, 
and removing the cap or stopper which prevents the access of daylight, an 
enlarged and well-defined image will appear upon the ground glass at the 
larger end of the camera. Having focussed in the same manner as before, 
this image now presents itself ready to be photographed, on merely holding 
the camera properly to the sun, or reflecting its rays from the small con- 
cave mirror placed at this extremity of the instrument. And further, by 
removing altogether the larger mirror the apparatus will be suitable for 
taking miniature portraits of sizes varying from that of a grain of mustard 
