MEMORANDA. 63 
reflector is about three and a half inches in diameter, and the 
bull’s-eye condenser about two inches in diameter, and placed 
a little within the focus of the reflector. A shade is also 
provided. We have long used and recommended the addition 
of a silver reflector behind a lamp. It not only economises 
light, but for many purposes improves its quality, as objects 
may be illuminated almost entirely by the reflected light 
when the wick is turned low, and thus the glare of the direct 
flame is avoided. Mr. Bockett burns Belmontine, which 
gives a whiter light than paraffine.—Jnfellectual Observer. 
A Mechanical Finger for the Microscope.—This is the name 
which Mr. H. L. Smith, of Kenyon College, U.S., has given 
to a very ingenious mechanical appliance, which will provea 
boon to those microscopists who are engaged in the study of 
minute hard structures. Since the mere description of Mr. 
Smith’s invention occupies nearly three pages of ‘ Sillimann’s 
American Journal of Science’ (No. 123), we must refer our 
readers to this source for details. The instrument seems 
likely to be extremely useful in delicate manipulation, since 
it can be made to move about in every direction over the 
stage, and thus to convey minute objects from one part of the 
field to another—and this, too, with the greatest precision, 
and in the most gradual manner.—Lancet. 
Transmission of Slides by Post.—At the meeting of the 
Quekett Microscopical Club, held November 23rd, Mr. M. C. 
Cooke called attention to this subject, on account of the 
large proportion of broken slides which had come under his 
observation during the past two years. Sometimes he had 
received a dozen slides per week from as many different 
individuals, and insufficient packing was the rule, good 
packing the exception. Many persons only enveloped their 
slide in stiff paper, some in cardboard, and then enclosed 
them in their letters: such slides were invariably broken. 
Others sent slides in thin cardboard boxes, or wrapped in 
cotton-wool or wadding, and afterwards in cardboard: these 
were generally broken. Others again enclosed slides between 
thin strips of wood with small blocks, or corks at the ends or 
angles: these seldom travelled safely. The most successful 
mode of packing proved to be, either to enclose the slides (if 
more than one) in a small deal box; or, if single, to transmit 
them in the black paper cases sold by opticians. If these 
