234 THE AMEBIC AN MONTHLY [(3ctol,er, 



Photo-M icrograpliy.* 



By M. E. swan. 



The essential apparatus for this study are, a microscope, liaving a 

 short and wide body, a camera of the simplest construction, together 

 with a few dishes and reagents. 



It is an advantage to have an adjustable base-board on which to set 

 up the apparatus, but this is not absolutely essential. 



The camera can be made by any amateur joiner out of any light case, 

 such as a soap box, at a cost of next to nothing, the only part necessary 

 to purchase being a back, as it is called, and the cheapest form I know 

 is Lancaster's metal double back, which will carry two plates 3^^ x 4^^ 

 back to back, and costing 2s. 6d. 



A dark room is necessary to work in, but at night time there are 

 generally but few difficulties in the way of the photograplier, and a lit- 

 tle ingenuitv will generally succeed in darkening any ordinarily lighted 

 room even in daytime. My own work-room is rendered suitable for 

 photography in less than ten seconds by lifting a canvas and paper screen 

 into the window space and securing it thereby two turn buttons. This 

 screen has a square hole containing a sliding piece of ruby glass, which 

 was the most expensive part of the whole thing, which did not cost two 

 shillings to make. A connection must be made to adapt the tube of 

 the microscope to the lens hole of the camera, but even this may 

 be dispensed with and a black cloth used to stop any stray light en- 

 tering. 



The light may be either daylight or artificial, and the latter, except 

 under cettain circumstances, is generally preferable, being more man- 

 ageable, and further, as most of my work is done at night, is absolutely 

 necessary. A paraffin lamp is all that is needed to supply the light, 

 anfl if a flat flame is used the edge of the flame should be used as the 

 source. The bull's-eye condenser is used so that a bright image of the 

 flame is focussed on the object, and the camera being in position the 

 object is focussed on the ground glass of the camera. 



A velvet-lined tube should be inserted into the body of the micro- 

 scope to prevent central flare. A good " fine adjustment " to the mi- 

 croscope is desirable, one that acts readily and accurately both in 

 approaching and withdrawing from the object, and if its movement is 

 truly in the optical axis of the instrument (which unfortunately is very 

 rarely the case), so much the better when photographing diflerent ob- 

 jects which do not lie all in one plane. 



The focussing screen now demands attention ; ordinary ground glass 

 is too coarse, except for very rough focussing. An improvement is to 

 varnish a sheet of plain glass with an ethereal solution of sandarach, 

 which dries with a very fine, smooth surface. A still better screen is a 

 polished glass with a few lines ruled on it. The image on such a screen 

 is invisible to the eye alone, l)ut may be viewed with a lens, and when 

 the image and the lines on the glass both appear equally sharp, the 

 best focus has been ol>tained. 



Perhaps the best method is to have a wooden screen perforated with 

 holes, into which a spare eye-piece is slipped to such a depth that the 

 diaphragm coincides with the plane in which the plate lies in the 



* Read at a meeting of the London Chemists' Assistants Association. 



