Wenham, on Microscopic Photography. 
3 
of recording them for the guidance of other experimentalists, 
for I have a strong belief that such an investigation may end 
in a useful result. There can be no doubt that it is a desi- 
deratum to discover a composition for a photographic fusee^ so 
to term it, that will burn for a sufficient period of time, and 
with the requisite actinic intensity for obtaining, not only 
microscopic impressions, but also nocturnal, or underground 
photographs. I trust, therefore, that this subject may be taken 
in hand by some one more practically conversant with the 
details of pyrotechnic chemistry than myself. 
There is no light that has hitherto been found that will give 
results at all equal to those to be obtained by the use of sun- 
light. The method that I have adopted for applying it, is simply 
to use the ordinary table microscope as a solar one. A room is 
selected, to the window of which sunlight must have free 
access ; this is closed by a shutter, having an aperture at the 
lower end of about three inches in diameter ; below this is 
placed a level table or bench at a convenient height, so that 
when the microscope body is in a horizontal position, its axis 
may coincide with the centre of the aperture in the shutter. 
Outside the latter is fixed a solar reflector, which may be 
adjusted from the inside, or more simply through a sleeve 
fastened around a hole in the shutter ; in this case the mirror 
may be mounted entirely in a wooden frame. 
With this arrangement the course of proceeding is as fol- 
lows : having clamped and adjusted the object on the stage 
of the microscope, place it horizontally against the aperture 
in the shutter, remove the eye-piece, and throw sunlight 
through the object by means of the solar reflector ; lay a black 
cloth around the microscope so as to stop out all extraneous 
light ; then, by properly focussing, a distinct image may be 
obtained upon a paper screen held at various distances. 
The stand for supporting the collodion plate consists of a 
vertical piece of board with a heavy base ; the excited plate 
is held on to this by means of two undercut fillets at right- 
angles to each other. The stand may be set at various dis- 
tances along the horizontal bench, which also serves as a 
support for the microscope. 
The operation of taking the photograph is, first to adjust the 
mirror for light, and then to focus the image on a card placed 
in the plane of the collodion surface ; next remove the card and 
lay it against the body of the microscope, so as to stop off all 
light ; then drop the sensitive plate into its place, snatch the 
card away, and quickly replace it again, so as to let the image 
of the object fall upon the plate : a fraction of a second is 
oftentimes sufficient. I prefer a rather slow collodion, and if 
h 2 
