1902] MICROSCOPICAL JOURNAL. 59 
that this form of tube has been used to contain Canada 
balsam with satisfactory results, and the writer referred 
to, determined to try how such tubes would do for immer- 
sion oil, although he was warned that the metal might 
have some deleterious effect upon the optical properties 
of the oil. After a year’s experience he is able to state 
that the tubes have proved to be quite free from the faults 
which characterize the bottles, and that the oil is as clear, 
colorless, and thin as when first made, and there is no in- 
dication of change in its refractive index. Which of our 
opticians will be the first to put immersion oil and Can- 
ada balsam in this form ? 
Roya Microscopicat Socrrry, December 18.—Messrs 
R & J. Beck exhibited a new micrometer microscope, the 
body of which was made to traverse acrossa long stage 
by means of a fine screw, the milled head of which was 
divided so as to indicate a movement of 1-100th milli- 
metre. ‘T’he body could also be placed in a horizontal po- 
sition, when it could be used as a telescope to measure dis- 
tant objects. Mr. F. W. Watson Baker exhibited a num- 
ber of microscopic specimens illustrating the development 
and the structure of eyes. They were shown under twenty 
microscopes, and were the most perfect sections that could 
be obtained from the best preparers in this country and 
abroad. Mr. EH. M. Nelson sent three notes, which in his 
absence were read by the Secretary. The first was a 
description of Holtzapffel’s microscope. The date of it is 
1830, and in it are found four original devices: (1) It po- 
sesses a clamp foot for clamping the instrument to the 
edge of a table, pre-dating a similar device of Varley’s in 
1831 ; (2) the back of the mirror is flat polished brass, so 
that monochromatic light may be reflected by it; (3) the 
stage is focussed by an eccentric which differs from and 
pre-dates the somewhat analogous devices of Pacini and 
Plossl; (4) the movement of the lens-holder is by means 
of a steel tape and pinion. 
