The
crystal in question consisted of ..., which, as those who manufactured
it for me are aware, admits of being cast with a perfection and
equality of structure throughout unattainable with ordinary glass, and
wrought to a certainty and accuracy of curvature which the most
patient and laborious polishing can hardly give to the lenses even of
moderate-sized telescopes, whether made of glass or metal, and is
singularly impervious to heat. I had so calculated the curvature that
several eye-pieces of different magnifying powers which I carried with
me might be adapted equally to any of the window lenses, and throw a
perfect image, magnified by 100, 1000, or 5000, upon mirrors properly
placed.
I carpeted the floor with several alternate layers of cork and cloth.
At one end I placed my couch, table, bookshelves, and other necessary
furniture, with all the stores needed for my voyage, and with a
further weight sufficient to preserve equilibrium. At the other I made
a garden with soil three feet deep and five feet in width, divided
into two parts so as to permit access to the windows.
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