ZOOLOGY AND BOl’ANY, MICROSCOPY, ETC. 
859 
the new system of micrometer-screw,* with divided head indicating the 
1/400 part of a mm. The double plane and concave mirror is mounted 
on joints. The draw-tube is divided into millimetres. 
The whole illuminating system, consisting of a wide-angled Abbe 
condenser (N.A. 1*40) with iris diaphragm, is raised or lowered by the 
screw Y. The iris diaphragm is mounted on the wheel R, worked by 
the tangent screw T, which by a very 
slight movement causes the aperture of 
the diaphragm to pass from the centre to 
the periphery of the condenser. The 
handle I serves to open and close the 
diaphragm. 
Fig. 93. 
Fine- Adjustment of the Beck Patho- 
logical Microscope.! — The fine-adjust- 
ment of Beck’s new Pathological Micro- 
scope is stated to be one of the most 
sensitive and delicate fine-adjustments 
yet produced. It is constructed as 
shown in the accompanying figure. The 
body of the instrument is supported 
upon the barrel D D ; this barrel is accu- 
rately and smoothly fitted to the tri- 
angular core E E. At the top of the 
barrel D D is screwed the cap G, to 
which is attached the rod C. This rod 
passes through the centre of the core 
E E, and connects with the lever arm A 
at B. The action of the spring J which 
is wrapped spirally around the rod C 
raises the body of the Microscope and 
holds the lever arm A tightly against 
the screw arm F. The slightest motion, 
therefore, of the screw F is communi- 
cated through the lever A and the rod C 
to the body of the Microscope. 
The great delicacy of this arrangement will be appreciated when it 
is noticed that the distance from I H is double the distance I B, there- 
fore any motion at B is only half that at H. This adjustment is one 
of the most delicate made for use with high powers. 
W ' 
(2) Eye-pieces and Objectives. 
A Recent Improvement in the Microscope, j; — “L. H.” writes as 
follows : — “ I purchased some time back a valuable Microscope, which 
cost over 20 Z. with accessories, but I was not satisfied with it, and 
neither have I ever been satisfied with those instruments exhibited at 
London microscopal soirees at Morley Hall, Hackney, although of 
celebrated manufacturers. The Zeiss lenses, also, have not come up to 
* See this Journal, 1886, p. 837. f Microscope, xii. (1892) pp. 183-4. 
X Engl. Mech., lvi. (1892) p. 17. 
3 m 2 
