ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
87 
MICROSCOPY. 
a. Instruments, Accessories, &c.* 
(1) Stands. 
Report of the Committee of the American Society of Microscopists 
on Uniformity of Tub e-length, f — The following Report has been issued 
by the American Society of Microscopists : — “ Believing in the desirability 
of a uniform tube-length we unanimously recommend : — 
(1) That the parts of the Microscope included in the tube-length 
should be the same by all opticians, and that the parts included should 
be those between the upper end of the tube where the ocular is inserted 
and the lower end of the tube where the objective is inserted. 
(2) That the actual extent of tube-length as defined in section 1 — Be, 
for the short or Continental tube, 160 mm. or 6*3 in., and 8J in. or 
216 mm. for the long tube, and that the draw-tube of the Microscope 
possess two special marks indicating these standard lengths. 
(3) That oculars be made par-focal, and that the par-focal plane be 
coincident with that of the upper end of the tube. 
(4) That the mounting of all objectives of 1/4 in. and shorter focus 
should be such as to bring the optical centre of the objective 1J in. 
below the shoulder ; and that all objectives be marked with the tube- 
length for which they are corrected. 
(5) That non-adjustable objectives be corrected for cover-glass from 
15/100 to 20/100 mm. (1/130 to 1/170 in.) in thickness. 
These recommendations give a distance of 10 in. (251 mm.) between 
the par-focal plane of the ocular and the optical centre of the objective 
for the long tube, and are essentially in accord with the actual practice 
of opticians. 
At the request of the committee, a joint conference was held with 
the opticians belonging to the society and present at the meeting. 
They expressed their belief in the entire practicability of the above 
recommendations, and a willingness to adopt them. — Signed, Simon H. 
Gage, A. Clifford Mercer, Prof. Barr.” 
Swift and Son’s Improved Student’s Microscope —At the October 
meeting of the Society, Mr. G. C. Karop exhibited and described this 
instrument (fig. 1), which he said had been brought out by Messrs. 
Swift at his suggestion. The aim was to produce a Student’s Microscope 
of a superior design, with which high-class optical appliances could be 
used. 
The body-tube is made to take the full-size eye-pieces in general 
use, and short enough to work with objectives adjusted to the Continental 
tube-length. 
A draw-tube lengthens to the English standard of 10 in. The 
bearing carrying the body is made longer than usual in students’ 
instruments, so as to give greater firmness with low-power objectives. 
The fine-adjustment was that known as Campbell’s Differential Screw 
* This subdivision contains (1) Stands; (2) Eye-pieces and Objectives; (3) Illu- 
minating and other Apparatus ; (4) Photomicrography ; (5) Microscopical Optics 
and Manipulation ; (6) Miscellaneous. f Microscope, x. (1890) p. 297. 
