outward pressure of the air inside.  Partly for these reasons, and partly because its electric character makes it especially capable of being rendered at will pervious or impervious to the apergic current, I resolved to make the outer and inner walls of an alloy of ..., while the space between should be filled up with a mass of concrete or cement, in its nature less penetrable to heat than any other substance which Nature has furnished or the wit of man constructed from her materials.  The materials of this cement and their proportions were as follows. [2]

* * * * *

Briefly, having determined to take advantage of the approaching opposition of Mars in MDCCCXX ... [3], I had my vessel constructed with walls three feet thick, of which the outer six and the inner three inches were formed of the metalloid.  In shape my Astronaut somewhat resembled the form of an antique Dutch East-Indiaman, being widest and longest in a plane equidistant from floor and ceiling, the sides and ends sloping outwards from the floor and again inwards towards the roof.  The deck and keel, however, were absolutely flat, and each one hundred feet in length and fifty in breadth, the height of the vessel being about twenty feet.  In the centre of the floor and in that of the roof respectively I placed a large lens of crystal, intended to act as a window in the first instance, the lower to admit the rays of the Sun, while through the upper I should discern the star towards which I was steering.  The floor, being much heavier than the rest of the vessel, would naturally be turned downwards; that is, during the greater part of the voyage towards the Sun.  I placed a similar lens in the centre of each of the four sides, with two plane windows of the same material, one in the upper, the other in the lower half of the wall, to enable me to discern any object in whatever direction.  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.  I filled