116 BEALE, ON OBTAINING LITHOGRAPHS. 
upon the scale corresponds to a magnifying power of one hundred, instead 
of ten diameters. Any fractional parts can be readily estimated if we have 
a very accurately divided scale. This process must be repeated for every 
object-glass, as well as for each different eye-piece employed with the several 
objectives. 
“1 ascertain the Diameter of an Object.—If an object be substituted for 
the micrometer, and its outline carefully traced upon paper, its dimensions 
may of course be easily ascertained by comparison with the micrometer lines, 
The magnified power used being the same in both cases. 
“Tn order to apply this plan to microscopical drawings generally, the fol- 
lowing seems to be the simplest method of proceeding, and saves mucli 
trouble. Scales are carefully drawn upou gummed paper; the magnifying 
power, and the micrometer employed, being written against them as repre- 
sented in the plates. If a number are drawn together one of the rows can 
be cut off and appended to the paper upon which the drawing, magnified of 
course to the same degree, has been made. This is the plan | have followed 
in all the drawings which illustrate my observations, and the scales have 
been copied in the lithographs. All magnifying glasses of the same focus 
do not magnify in precisely the same degree, so that it is necessary for every 
observer to ascertain for himself the magnifying power of his lenses, and he 
may construct little tables in the manner I have described. 
“In order to make an accurate microscopical drawing, the image of the 
object is carefully traced on paper with the aid of the glass-reflector, and 
afterwards finished by the aid of the eye alone. In order to obtain the size 
accurately, care must be taken that the distance between the reflector and 
the paper is the same as that between the former and the object-glass. The 
drawing having been finished, one of the scales made as above described may 
be gummed on in one corner of the paper. 
“Of Drawing Objects in the Microscope, from which it is intended to take 
Lithographs.—The lithographs illustrating the papers in the present number 
have been made by copying the image, with the aid of the reflector, on trans- 
fer-paper, with lithographic ink or chalk.* 
“The drawing on the transfer-paper being complete, is transferred to a 
finely grained lithographic stone and properly fixed; impressions may then 
be taken off.’ 
All the papers in this number have greater or less merit, 
and we can cordially recommend Dr. Beale’s ‘ Archives’ to 
the patronage of our medical readers. 
* “The best transfer-paper for this purpose is made of India paper. The 
ink and chalk can be purchased at any lithographer’s. Fluid lithographic 
ink answers very well, and was used in making the drawings.” 
t “The drawings have all been carefully copied from the objects them- 
selves on transfer-paper in my house, and then transferred to the stone. 
The transfers have been made and the impressions printed off by Messrs. 
Harrison and Sons, of St. Martin’s Lane, and it is only right that I should 
thank those gentlemen for the trouble and interest they have taken, and for 
the kindness which they and their workmen have always shown in carrying 
out this plan of producing the drawings, as well as other suggestions which . 
have been rade.” 
