of the two primary necessaries of animal and vegetable life. That Mars has seas, clouds, and an atmosphere was generally admitted, and I held it to be beyond question. Of Venus, owing to her extraordinary brilliancy, to the fact that when nearest to the Earth a very small portion of her lighted surface is visible to us, and above all to her dense cloud-envelope, very little was known; and though I cherished the intention to visit her even more earnestly than my resolve to reach the probably less attractive planet Mars, I determined to begin with that voyage of which the conditions and the probable result were most obvious and certain. I preferred, moreover, in the first instance, to employ the apergy as a propelling rather than as a resisting force. Now, after passing beyond the immediate sphere of the Earth's attraction, it is plain that in going towards Mars I should be departing from the Sun, relying upon the apergy to overcome his attraction; whereas in seeking to attain Venus I should be approaching the Sun, relying for my main motive power upon that tremendous attraction, and employing the apergy only to moderate the rate of movement and control its direction. The latter appeared to me the more delicate, difficult, and perhaps dangerous task of the two; and I resolved to defer it until after I had acquired some practical experience and dexterity in the control of my machinery.
It was expedient, of course, to make my vessel as light as possible, and, at the same time, as large as considerations of weight would admit. But it was of paramount importance to have walls of great thickness, in order to prevent the penetration of the outer cold of space, or rather the outward passage into that
