570 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
least theoretically. But let us see how fine a theory it is. The thick- 
ness of a sheet of my gummed paper, measured by a micrometer, is 
about 1/1000 in., determined by bolding the paper edgewise in a stage- 
forceps under the Microscope. In case we are using a power of 500 
diameters, the field will be about 1/100 in. across. Now, by proportion, 
the length of the slide is to the diameter of the field as the thickness of 
the label is to the inclination of the field, or x. Then 1J in., 1/100 in., 
1/1000 in. x, 7/4 x = 1/100,000, x = 1/175,000 in., for the variation 
from a theoretical true level, or in the breadth of vision with a 1/5 or 
1/6 objective; and if we are using a 2-in., 1/10 of that, which is 
1/17,500, is out of level, on account of the level on the under side of 
one end. 
Where is the instrument maker, however skilful, who can construct a 
stand the tubes of which shall vary so little as that from a true perpen- 
dicular to the stage ? The best slides may vary more than that in the 
thickness of ends. Stands that raise one side of the stage by the fine- 
adjustment, as do some of the Acme stands of J. W. Queen & Co., disregard 
this principle in a very much larger degree without detriment. This is 
my plea for the short slide. Will the reader allow me to submit it for 
its worth, without expecting to see its general adoption, but hoping to 
help some one who, like myself, is often bothered about the close working 
objectives, that in spite of all carefulness, occasionally impinge upon the 
cover-glass? Backing downwards is very troublesome to old eyes using 
high powers. They find it difficult to look across the stage to reach 
below the focus, where the looking distance is 1/100 in. or less. Let 
all such try my safety slide, and they will find its perfect working con- 
venience an ample compensation for being out of fashion or for lack of 
imaginary beauty, and after using it often and long, and trying it faith- 
fully and well, they will, like myself, never wish to see another long 
slide for ordinary microscopical work.” 
(6) Miscellaneous. 
Squire’s “ Methods and Formulse ” used in Microscopical Examina- 
tion.* — The usefulness of this compilation will be obvious to any 
histologist, as it contains formulae and advice for microscopical work in 
all branches of the subject save that of section-cutting. Great numbers 
of the formulae are certainly correct, and the advantage of having these 
in a small and compendious volume will, no doubt, be evident to a great 
number of workers. For a first attempt the work is very excellent, but 
the formulae for bacteria staining will require revision and amplification 
for a second edition. For example, no mention is made of the best and 
most rapid method of staining tubercle bacilli, the Neelsen-Glorieux, 
nor the most elegant and satisfactory, that of Czaplewski. It is satis- 
factory to note that no allusion is made to methyl-blue, a pigment which 
might easily be dispensed with, while with regard to methylen-blue, we 
would suggest the addition of a formula with an acidity corresponding 
to the alkalinity of Loeffler’s methylen-blue. 
Microscopical Examination of Potable Water. | — Mr. G. W. Bafter 
has just brought out a neat and practical little volume which deals with 
* ‘ Methods and Formula),’ J. and A. Churchill, 1892, 93 pp. 
t Van Nostrand’s Science Series, New York, 1892, 18mo, 160 pp. 
