42 
PRACTICAL PHOTO-MICROGRAPHY. 
several in the provinces, and several on the Continent, # 
may be trusted to supply apparatus well fitted for the 
work. But we venture to assert that any signal depar¬ 
ture from the principles here laid down will be sugges¬ 
tive of imperfection in design. 
The most elaborate instrument we have ever seen 
is one constructed by Zeiss, and costing about ^200. 
Needless to say, the design and workmanship are 
alike admirable, but having no experience of the in¬ 
strument, nor of any similar, we cannot criticise its 
performance. 
Vertical Apparatus. 
Some first-rate authorities, among whom we may 
mention Dr. H. Van Heurck, of Antwerp, prefer to use 
for general work, vertical cameras; while we fail to see 
the advantages of this for ordinary work, we are aware 
that it is sometimes necessary, as when we have to deal 
with liquid preparations, or such as cannot be covered 
or enclosed in a cell. And when we came to work out 
an apparatus to be used on the vertical we discovered 
certain great advantages hanging on this method which 
cause us to devote particular attention to the matter 
here. 
In the first place, our apparatus, fig. 10, being clamped 
in all its parts to the base-board, can be quite well used 
vertically, and it has been so used with success. But 
we figure the apparatus of Dr. Van Heurck, which is 
made by Messrs. Watson for vertical use alone. It 
consists of an oblong box steadily mounted on four legs 
of such length that the ocular end of the microscope 
