( 57 ) 
On the Application of Photography to the Representation of 
Microscopic Objects. By Joseph Delves, Esq. Commu- 
nicated by Mr. Bowerbank. (Read Oct. 27, 1852.) 
At the present time, when the microscope is contributing 
valuable aid in nearly every department of science, and its 
uses as an instrument are more generally known, it becomes of 
the greatest importance to possess some method more truthful 
than those hitherto adopted for copying the beautiful images 
of the achromatic object-glass. 
The recent discoveries in photography render its appli- 
cation to the microscope a subject for much consideration, 
since only by its assistance can we hope to obtain trustworthy 
impressions of objects so delicate and minute. I would, there- 
fore, beg to submit to the consideration of the Society the 
method I have adopted for producing these copies ; and as 
an illustration of the successful application of Photography to 
the microscope, I have the honour of presenting the specimens 
which I have recently obtained. 
I must, however, beg to state that others have an earlier 
claim than myself to this application ; but with so little 
success had it previously been carried out, that I believe I 
am correct in saying it has been generally abandoned as a 
means of depicting microscopic objects. But for the satis- 
factory result it is only necessary to refer to plate VII. 
The only arrangement necessary for the purpose is the 
addition to the microscope of a dark chamber, similar to that 
of the camera obscura, having at one end an aperture for the 
insertion of the eye-piece end of the compound body, and at 
the other a groove for carrying the ground-glass plate. 
This dark chamber should not exceed 24 inches in length 
(the size which I have found best to adopt) : if extended 
beyond this, the pencil of light transmitted by the object- 
glass is diffused over too large a surface, and a faint and 
unsatisfactory picture is the result. The specimens ex- 
hibited were taken at this distance, which has the additional 
advantage of producing a picture, in size very nearly equal to 
the object as seen in the microscope. The eye-piece must be 
removed from the compound body, and the object (being well 
illuminated by reflection from the concave mirror) must be 
adjusted and focused upon the ground-glass plate. In the 
production of positive pictures a slight difficulty here arises, 
dependent upon the " over-correction of the object-glass. 
The effect of this " over-correction "is to project the blue 
rays of light beyond the other rays of the spectrum, and as 
the chemical properties of light reside in the violet and blue 
VOL. I. / 
