"Yes, the design resembles that of a torpedo considerably," replied the doctor, and referring to the sectional blue-print he began explaining the construction.
"This outer covering is a crust of graphite or black lead, inside which is a two-inch layer of asbestos. Both of these resist enormous heats, and they will prevent our burning by friction with atmospheres, and protect us against extremes of cold. Also, when we are ready, they will enable us to visit planets about whose cooled condition we are not certain. We might touch safely for a short time on a molten planet with this covering.
"Next comes the general outer framework of steel, just within which, and completely surrounding the living compartments, are the chambers for the storage of condensed air for use on the trip. These chambers are lined inside with another layer of asbestos. Now, air being a comparatively poor conductor of heat, and asbestos one of the best non-conductors we know of, this insures a stable temperature of the living compartments, regardless of the condition without, whether of extreme heat or extreme cold. Afterward comes the inner framework of steel, and lastly a wainscotting of hard wood to give the compartments a finish."
"How large are these living rooms?" I inquired.
"The rear one is four feet high and eight feet long. The forward one, designed for my own use, is longer, and must contain a good-size telescope and all my scientific instruments. The apparatus with which I produce the currents is built into the left wall, and it acts on the steel work of the projectile only. The rear compartment has a sideboard for preparing meals, which will have to be wholly of bread, biscuits, and various tinned vegetables and meats. We shall not attempt any cooking."
"But are there no windows for looking out?" I queried.
"Certainly, there are two of them, made of thick mica. One is directly in the front end, through which my telescope will look. The other is in the port-hole in the rear end. Each window is provided with an outer shutter of asbestos, which can be closed in case of great heat or cold. You will notice the two compartments can be separated by an air-tight plunger, fitting into the aperture between them. It will be necessary for both of us to occupy the same compartment while the air is being changed in the other. The foul air will be forced outside by a powerful pump until a partial vacuum is created. Then a certain measure of condensed air is emptied in, and expands until the barometer in that compartment indicates a proper pressure."
"The air will be made to order while you wait, then?" I put in.
"That is exactly what will be done in a more literal manner than you may suppose!" exclaimed the doctor. "This air problem is a most interesting one, for we must educate ourselves on the trip to use the sort of atmosphere we expect to find when we land. For instance, going to Mars we must use an atmosphere more and more rarefied each day, until gradually we become used to the thin air we expect to find there. Of course, there is an especially designed barometer and thermometer, capable of being read in the rear compartment, but exposed outside near the rudder. The barometer will give us the pressure of the earthly atmosphere as it becomes more and more rare with our ascent. It will show us what pressure there is of the ether, which may vary considerably, depending on our nearness to heavenly bodies. It will also immediately indicate to us when we are entering any new atmosphere. When we have arrived at Mars, we shall observe the exact pressure of the Martian air, and then manufacture one of the same pressure inside, and try breathing it before we venture out. The thermometer will give us the temperature of the ether, will indicate the loss of heat as we leave the sun, and will show us the Martian temperature before we venture into it."
"But you have said the condensed air will be used to resist the outer heat. This will certainly make it so hot it will be unfit to breathe," I interposed.