For this particular subject,
lenses must be ground firstly to spherical, and then to curves of
conic sections, so as to eliminate spherical aberration from each
lens; so that it will be observed that this subject is not
without its difficulties.
"About a month ago (September, 1883), I determined to put to the
test the statement of some of our theorists, that the surface of
a rotating fluid is either a parabola or a hyperbola. I found by
experiment that it is neither, but an approximation to the
tractrix (a modification of the catenary), if anything definite;
as indeed one, on thinking over the matter, might feel certain it
would be--the tractrix being the curve of least friction.
"In astronomy, I have really done very little beyond mere
algebraical working of the fundamental theorems, and a little
casual observation of the telescope. So far, I must own, I have
taken more pleasure in the theory and construction of the
telescope, than in its use."
Such is Samuel Lancaster's history of the growth and development
of his mind. I do not think there is anything more interesting
in the 'Pursuit of Knowledge under Difficulties.' His life has
been a gallant endeavour to win further knowledge, though too
much at the expense of a constitution originally delicate. He
pursues science with patience and determination, and wooes truth
with the ardour of a lover.
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