CHAPTER II. 
THE MICROSCOPE AND ITS PARTS. 
T^VERY microscope intended for serious use must 
have certain qualities if satisfactory performance 
is to be expected. The fitting of every part must be 
of the most accurate and lasting workmanship; its 
general design must be convenient and handy ; and it 
must be more or less “ solid ” and entirely steady. 
These qualities are required for photo-micrography in 
a special degree, for the test of projecting the image on 
a plate many inches distant from the ocular, and of 
keeping it absolutely steady there for many seconds or 
even minutes, is much more severe than that of merely 
projecting an image on the retina, the hand being on 
the fine adjustment all the time to correct any altera¬ 
tion that may take place in the relation between the 
various parts. Consequently the greatest care should 
be taken in selecting a “ stand ” for our work ; one that 
may answer fairly well for ordinary observation may 
utterly break down under the test of photography. Let 
the conveniences of the pattern be ever so great, let the 
instrument have every known “ movement,” all is of no 
value if the instrument is not absolutely steady, rigid 
in every part, and accurate in every fitting. 
