788 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
C3) Illuminating- and other Apparatus. 
Substages for Students’ Microscopes. — The following interesting 
correspondence appeared in the pages of the ‘ English Mechanic — 
“ Under this heading Messrs. Watson and Sons reproduce, if I 
mistake not, a figure of the underpart of the stage of one of their 
Microscopes, which was published in the ‘ E.M.’ a year or two ago. 
They appear to claim for it some originality of design, and bring it 
forward again, as if it wholly superseded the necessity for Swift and 
Sons’ rival production, notwithstanding the fact that such rival production 
is recommended by the Secretary of the Quekett Microscopical Club 
(vide Report of Proceedings Q.M.C., ‘ E.M.,’ p. 185). 
Examining Messrs. Watson’s figure with a somewhat experienced 
eye, I note that the substage is not mounted on a substantial tail-piece, 
but is merely connected with the stage proper by a screw, on which it 
pivots out of the axis, the axial position being roughly secured by a stop- 
pin ; the centering is then effected by the two projecting screws on the 
circumference of the substage acting upon a movable inner ring or tube 
in which the condenser or other apparatus is applied. 
This system of pivoting the substage has long been in use on the 
Continent for all classes of Microscopes, from the most elaborate down 
to the commonest types of so-called students’ instruments. It is a bad 
system — bad in the Johnsonian “ leg-of-mutton” sense — bad from every 
point of view. 
A focusing and centering substage can hardly be too substantially 
connected with the Microscope, for it has to suffer more rough handling 
than any other part of the instrument. The fewer movements it has 
beyond those actually needed for use, the better ; for every additional 
joint or slide-bearing brings in its quota of unsteadiness, making addi- 
tional demands on the observer’s watchfulness and patience in securing 
exactness of adjustment. 
The only satisfactory arrangements of substage yet devised act by 
rack-and-pinion on a fixed tail-piece. 
Many attempts have been made, both in Europe and America, to 
devise means for focusing the condenser of a less expensive character 
than the rack-and-pinion ; but they have all been found radically bad in 
practice by those who were familiar with the conveniences of the rack- 
and-pinion, and who have been called upon to test the various systems 
devised in substitution. 
In the older models of drum Microscopes ( Microscopes a tambour) of 
Georges Oberhauser — who was probably the first to apply mechanism to 
focus the substage condenser of the achromatic Microscope— the 
substage socket was a fixture beneath the stage, and the condenser tube 
sliding in it was provided with stud-pins on either side, on which a 
forked lever engaged, the free end of the lever projecting slightly 
through a vertical slot in the drum base, so that by its movement up 
^ or down the condenser was adjusted beneath the object. This arrange- 
ment was generally combined with some primitive means of centering the 
condenser with a screw-driver, such centering being on the “ once for all ” 
Engl. Mech., lii. (1890) pp. 228, 229, 251, 271. 
