150 THE MICROSCOPICAL NEWS. 
same pessimistic finality has been pronounced in every age of every 
art. It is true we do not know in what direction to look for any 
advance as regards the microscope, but none the less it may be 
achieved. Mr. Crisp’s collection shows what has been done and is 
being done for the perfection of the instrument; it thus warns the 
inventor of the mistakes of the past, and concentrates his powers 
on the most productive area for further improvement.—LZglish 
Mechanic. 
THE WINDSOR AND ETON SCIENTIFIC 
SOCIETY: 
T the last monthly meeting of the Windsor and Eton Scientific 
Society, Mr. Edgar Thurston, curator of the Anatomical 
Museum, King’s College, London, read a paper on “‘ The Micros- 
cope, its Construction and Manipulation.” 
Mr. Thurston commenced by dwelling upon the importance of 
good illumination of microscopes, observing that if the illumination 
of an object was neglected the advantage of using good objectives 
was entirely lost. Microscopes were mainly built up according to 
two types, the bar movement or Ross model, and the Jackson 
model. Having described these, he expressed his preference for 
the Ross model when its workmanship was well executed. The 
body of a microscope, he said, with the objective, should measure 
ten inches, which is a very good standard, as it is the distance at 
which a person with normal vision holds a book so as to read com- 
fortably, without straining the eyes. For drawing purposes, with 
the camera lucida, or neutral tint reflector, the standard distance 
from the centre of the eye-piece to the drawing surface is likewise 
ten inches. It is very important that the bodies of microscopes 
should be constructed of uniform length, as objectives, which are 
corrected for a certain length of body, will not work satisfactorily 
at any other length. An objective, for example, corrected for a 
body eight and a half inches in length, will not work well with a 
body only seven inches in length. Increase of magnifying power 
should not be obtained by lengthening the body by means of a 
draw-tube, as such a proceeding is always attended by loss of 
definition. 
After some remarks on the eye-piece, the best form of which he 
said was the one in general use, Huyghenian, composed of two 
plano-convex lenses. A lens constructed of uniform material will 
not form a single white image of a white object, but a series of 
