THE MICROSCOPE. 
by organ, we must call to our aid the higher class of power. In 
tine, a complete microscopic analysis of an individual object will 
require that it should be viewed successively with a series of 
gradually increasing powers. 
10. But magnifying powers, to whatever extent they may be 
carried, will be of no avail if the image produced by the object-glass 
be not perfectly distinct and well defined; and it will be evident 
upon the slightest consideration, that any minute imperfections 
which may exist in its delineation, will be rendered more and 
more glaring and intolerable, the higher the magnifying power 
under which it is viewed. 
With a common magnifying glass, or simple microscope, we 
view the object itself, and are subject to no other optical imper¬ 
fections in our perception of it, than such as may arise from the 
imperfection of the lenses through which we view it; and since 
with such instruments the magnifying power can never be con¬ 
siderable, small defects of delineation are never perceptible. It is 
quite otherwise, however, with the class of instruments now under 
consideration, where magnifying powers, from 1000 to 2000 of the 
linear dimensions, are often brought into play. 
These circumstances render it indispensable that the image of 
the object produced by the object-glass, and viewed through the 
eye-glass, should have the utmost attainable distinctness of de¬ 
lineation ; not only as regards its outline, but also as respects the 
most minute details of its structure and colouring. 
11. Now the solution of this problem, presented to scientific and 
practical men the most enormous difficulties ; difficulties so great 
as to have been regarded, by some of the highest scientific autho¬ 
rities of the last half-century, as absolutely insurmountable. 
Happily, nevertheless, the problem has been solved ; and without 
disparagement to the great lights of science, we must admit that 
its solution has been mainly the work of practical opticians. It 
is true that the general principles upon which the form and 
material of the lenses depend, were the result of profound mathe¬ 
matical research, but these principles were established and well 
understood at the moment when the practical solution of the pro¬ 
blem was, by scientific authorities themselves, pronounced to be 
all but impossible. Opticians, stimulated by microscopists and 
amateurs, then applied themselves to the work, and by a long 
series of laborious and costly trials, attended with many and 
most discouraging failures, at length arrived at the production 
of optical combinations, which have rendered the microscope one 
of the most perfect instruments of philosophic research, and one, 
to the increasing powers of which, we can scarcely see how any 
limit can be assigned. 
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