ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
101 
Mr. Winspear, optician, Hull, for photomicrography, when focused on 
Pleurosigma formosum, led me to test its value photographically. Un- 
fortunately, I had to fall back on some old slow quarter-plates, and 
being without any guide as to exjmsure, I simply made use of my small 
camera arrangement, described in one of your almanacks, and attached 
it to the draw- tube of the Microscope, using for illumination a large 
paraffin lamp, and a crossed lens as a condenser. At the first trial a 
very fair image was obtained, using the develo])ing solution described 
ill the present ‘British Journal of Photography Almanac,’ 1890. It 
seemed evidently worth while to try another more magnified image, so 
I managed to centre a quarter-plate camera by means of a blackened 
card witli a central dark-lined paper tube fitted to the draw-tube of the 
Microscope, and made to fill uji the lens aperture in the camera. As 
soon as ready, I took a photomicrograjJi of Pleurosigma formosum, using 
the 1/12-in. bull’s-eye condenser and lamp, the little rod being set 
parallel to one set of lines on the diatom. The result I inclose for your 
notice, as it possibly may be one of the first negatives you may have 
seen ju-oduced under such conditions. Unfortunately it is a trifle over- 
developed, but with the naked eye, or better with a lens, you will see 
the effect that can be obtained by such a simple piece of apparatus. 
The value of the little rod as a condenser appears to me to rest chiefly 
in giving linear illumination of a convergent character, which can be 
directed in any position as regards the striation of lined objects. Some 
very curious effects can be brought out by keeping the eyes fixed on the 
object at the same time that the rod is gently rotated round the axis of 
the Microscope, and it is just possible some of the peculiarities in the 
structure of striated diatoms may be better brought out than with an 
all-round convergent illumiDation. There is one point that must be 
carefully observed to obtain the best result, which is to be careful to use 
it at its own focus, otherwise the image is pale or fogged. It is not 
pretended to offer this plan for anything more than a costless substitute 
for a costly j)iece of apparatus. It j)ossesses a certain value, but is not 
intended to compete^ in general excellence with a fiist-rate achromatic 
substage condenser. You will be able to judge for yourself. I should 
have liked to have tested rods of coloured glass, but could not put my 
hands on any suitable ; and there remains yet to try the rod with a 
right-angle prism, instead of the plane mirror or parallel light by means 
of the bull’s-eye condenser. To find the best j)osition of the rod requires 
a little trouble.” 
Maddox’s Small Glass Rod Illuminator. — Dr. Maddox refers to the 
preceding as follows : — “ In this age of rapidly advancing microscopy 
may I for a few moments crave the attention of the Fellows of the 
Society to the claims of a small piece, 1/2 in. long, of solid white or blue 
glass rod, about 1/5 or 1/6 in. in diameter, when used as an illumi- 
nator, and substituted fur an ordinary substage achromatic condenser. 
I ask this permission as several errors have crept into the pages of 
a w'eekly contemporary journal, through the incorrect statements of a 
wuiter who noticed an article on the use of the white glass rod, contri- 
buted to the ‘ British Journal of Photography ’ of December 13th, 1889. 
A few days since I mounted a piece of blue glass rod in the same 
manner, i. e. by fitting it horizontally at its widest diameter into a thin 
cell, which screw's on the top of a substage fitting which has its own 
