194 THE NORTHERN MICROSCOPIST. 


permanent dye and the latter imparts a much brighter color than 
iodine green. 
THE LIMITING DIAPHRAGM, OR APERTURE SHUTTER.—In the 
June number of the Journal of the R..M. S., when speaking of 
Dancer’s diaphragm holder, it is stated “that the object for which 
these diaphragms was suggested is not practically attainable.” This 
will cause a smile from those members of the Manchester Micros- 
copical Society who were present when Mr. G. E. Davis demon- 
strated the amount of penetration given to a Tolles one-inch 
objective of 35°, the aperture being reduced to 12°, and also the 
half-inch of 60° when reduced to 35°. Considering that the objects 
shown were such as would clearly demonstrate the practical value 
of the “shutter,” foraminifera, globular micro-fungi, &c., it is not 
a little surprising to find that the object sought after is “not prac- 
tically attainable.” The publications of the first-mentioned Society 
have always been characterised by the presence of theories advanced 
to show the impossibility of something which others have practically 
accomplished, and we do not think that such writers give sufficient 
credit to the practical optician for being able to accomplish any 
more than has actually been done. 
We do know that all objectives will not bear the reduction of 
aperture without impairing their performance, but we should be 
vely Sotry to possess a one-inch objective which would not bear 
reduction to 16° without injury to the image—but more of this 
in our next. Would it not be possible for contributors to the 
J-R.MLS. to sign or initial their articles ? Readers would then be 
able to observe any “ change of front” which often takes place in 
the opinions of contributors, 
Votvox Aureus. Wax CELis,—Mr. Thomas Whitelegge, of 
Ashton-under-Lyne, has sent us a goodly collection of this alga in 
fructification, he having discovered it in a pond near Ashton. He 
has also demonstrated to us a very simple method of making wax 
cells. A piece of glass tubing is first drawn out to a point so as to 
form a pipette, and this is filled with melted white wax. The slip 
upon which the cell is to be made is placed in the turntable, and 
while it is spinning, touched with the point of the wax pipette, 
previously heated so that the wax may flow out readily. A wax 
ring is thus made quite as easily as one of varnish, and if the ordi- 
nary pharmaceutical white wax be employed, it will adhere very 
tenaciously to the slide. It is obvious that many varieties of rings 
may be made by modifying the temperature of the wax or even by 
warming the slide, and as an Operation of this kind generally 
requires some little practice in order to obtain the best results, a 
few failures at the outset should not discourage the operator from 
further attempts. 



