88 
POPULAR SCIENCE REVIEW. 
the relative merits of the buWs-eye-condenser, metallic reflector, Lieherkuhn, 
jparaholic reflector, achromatic, and Gillet's condensers, are impartially dis- 
cussed, and much useful instruction is given relative to the methods of draw- 
ing an object. For the latter purpose Dr. Beale prefers what is called the 
tint glass reflector to the camera lucida, remarking that “ the simplest and 
cheapest reflector for microscopical drawing consists of a small piece of plate 
glass, slightly coloured, in order to improve its reflecting power, but still not 
so dark as to prevent an object being seen through it perfectly. This is 
arranged at an angle of 45° with the eye-glass, and the draughtsman can very 
easily follow his pencil on the paper.” There are some valuable hints given 
as to the mode of drawing upon wood and stone, and it is recommended that 
the student should learn the art of delineating with his own pencil the 
structures observed, for although “Mr. Tuffen West and one or two other 
gentlemen have taken up this kind of drawing and engraving, and have pro- 
duced most beautiful results,” yet no mere artist can make himself fully 
conversant with all the details of every branch of microscopic inquiry. On 
the subject of the measurement of objects Dr. Beale states his opinion that 
the most simple and efficacious method of ascertaining the size of specimens 
is by means of the stage micrometer and tint-glass reflector. The micrometer 
is first placed on the stage, and the instrument being arranged horizontally the 
scale is then, by the aid of the reflector, traced upon a sheet of paper, the 
object is then substituted for the micrometer, and the image being thrown on 
to the drawn scales, the measurement is easily achieved. Chapter III. 
contains an account of the difierent instruments required by the working 
microscopist, and under this head may be found concise descriptions of 
lamps, retort stands, tripods, brass-plates, and scalpels, Valentin’s knives, 
scissors, needles, forceps, slides, cells, &c. Here also we perceive that 
the writer furnishes the character, and receipts for the preparation of the 
several liquids necessary in the operation of mounting or setting up speci- 
mens, such, for example, as gold size, shellac, asphalt, marine glue, Canada 
balsam, gum, French cement, glycerine, naphtha and creosote, naphtha and 
water, carbolic acid, chromic acid, preservative gelatine, gelatine and 
glycerine, gum and glycerine, Goadby’s solution, Burnett’s solution, solution 
of chloride of calcium, alum, arsenic, arsenuretted hydrogen, and nitrogen. 
In describing how to manufacture cells for one’s own use the author gives 
the following useful information as to the perforation of thin glass : — 
“ I cement a square or circle of thin glass with marine glue to one of the 
circular or quadrangular rings of glass, used for making deep glass cells ; the 
hole in the centre being the exact size of that required to be made in the 
thin glass. When the marine glue is cold, a file is forced through the centre 
of the thin glass. The cracks thus produced do not run across that portion 
of the glass cemented by the marine glue. The edges may then be filed 
square, and the thin glass only requires to be warmed in order to remove it 
from the cell. It may now be fixed upon the slide at once, or cleaned with 
potash, and kept with others until required to be made into a cell.” 
The chapter on the preparation of tissues and their injection is well 
worthy of attention. After enumerating the many forms of injecting fluids 
now in use. Dr. Beale declares his preference for the transparent liquids, 
carmine and Prussian blue, and advances no less than seven reasons for their 
