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.