seen a good many changes, and is identified as the abode of Sir Isaac,
who had been knighted by Queen Anne in 1705. We visited it many years
ago. The part of the house most intimately associated with his name is
the little observatory perched on the roof. We were permitted to ascend
into that spot, to see it desecrated by its present use, for there we
found a shoemaker busy at his toil. A glass cupola probably crowned
the observatory in Newton's time, and evidently there was a window in
each of the four walls. So here he looked out on the London of nearly a
century and a half ago, hardly less crowded and smoky about the
neighborhood than now. Overhead, where Newton turned his eyes with most
interest, we know it was just the same; the same beautiful stars shining
out on a cold winter's night, the same planets sailing along the same
blue ocean, the same moon throwing its light over the same old city.
What observations, keen and searching, what calculations, intricate and
profound, what speculations, far-reaching and sublime, must there have
been, when one of the most gifted of mortals from that spot looked out
upon the heavens, and in thought went forth on voyages of discovery into
the distant regions of the universe! At the calm, still hour of
midnight, Sirius watching over the city of sleepers, Jupiter carrying
his brilliant lamp along his ancient pathway, every one of the
luminaries in the place appointed by Him who calleth them all by their
names--there stood the thoughtful man, with his reflecting telescope,
occupied with thoughts which we common mortals in vain endeavor to
conjecture.

The first department in the field which Newton explored with
characteristic success was the study of optics. Philosophers were busy
with inquiries into the nature of light. It had been long believed that
every colored ray is equally refracted when passing through a lens.
Newton determined to analyze the prismatic hues. He made a hole in a
window-shutter, and darkening the room, let in a portion of light, which
he passed through a prism. The _white_ sunbeam formed a circular image
on the opposite wall, but the _prismatic colors_ formed an image five
times as long as it was broad. He was curious to know how this came to
pass. Satisfied that the length of the image in the latter case did not
arise from any irregularity in his glass, or from any differences in the
incidence of light from different parts of the sun's disk, or from any
cu