794 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
“ The question between Messrs. Watson and myself relates to the 
advisability or not of retaining the pivoting movement of the mechanical 
substage in their Edinburgh Student’s Microscope, as shown in the 
figure they reproduced with letter 31741, p. 207. They point to the 
numbers of these Microscopes sold in proof that the system must be 
good ; whilst I, on the other hand, point to the mechanism itself in 
proof that the system is bad, and I will explain my views. 
The chief aim in the application of focusing and centering move- 
ments to the substage is to enable the worker to adjust the illumination 
with all desirable accuracy. Experts have long been striving to popularize 
the fact that unless a mechanical substage is provided the student is 
placed at a serious disadvantage, for he cannot otherwise get the best 
work out of his optical battery. 
In the most perfect Microscopes hitherto constructed, no efforts have 
been spared to make the mechanical substage thoroughly substantial 
and accurate, and its attachment to the main instrument as rigid as 
possible ; hence the outlay on the substage is a large item of the total 
cost of these instruments. 
In the less perfect Microscopes, which are also less costly, less 
expensive forms of mechanical substages have to be applied, and as the 
outlay is reduced, the construction naturally reaches a lower grade of 
general stability, until finally, in order to cut down the cost to the 
lowest point, the optician gives up the substantial connection of the 
fitting with the main instrument, and attaches the substage to the under 
face of the stage proper by a screw-pivot, as shown in Messrs. Watson’s 
figure. The prime motive for adopting the pivoting system originally — 
I do not say the prime motive of Messrs. Watson, but of the real origi- 
nators, the French or German manufacturers of low-class Microscopes 
for toy-shops, &c. — was to reduce the cost, for the attachment is of so 
inexpensive a character that I suppose it may be done for a shilling, and 
then carry a profit of 50 per cent. Such a system may be tolerable in 
toy Microscopes, where the substage is intended as a mere diaphragm 
carrier, and it was formerly much in vogue even for dissecting Micro- 
scopes, as made by Chevalier and others ; but when the substage has to 
carry centering arrangements on a rack-and-pinion movement on a tail- 
piece, the whole purpose of these appliances is frustrated by the speedy 
development of ‘ wobble ’ and general instability that disgust the 
critical worker. 
Good substage appliances are most essential adjuncts for all serious 
work, and they merit that the substage shall be soundly and substan- 
tially attached to the Microscope, with reasonable assurance that the 
condenser, &c., shall focus and centre accurately in the optic axis of the 
Microscope with the minimum of collimation error. These are the well- 
known conditions that should guide the optician in the application of 
an efficient substage to a student’s Microscope ; and they are not properly 
met by attaching it to the stage proper by a pivoting arrangement such 
as that figured by Messrs. Watson. 
The student cannot too soon learn that the firmness of his mechanical 
substage, its rigid attachment to the Microscope, either by a tail-piece 
or other fitting, is infinitely more important in practice than the liberty 
of swinging it aside. He may take it for granted that the construction 
