THE PALL MALL MAGAZINE
out the product of combustion. Thus, with the two cylinders, there was one explosion for every turn of the shaft.
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Over the Bois de Boulogne.
Wishing to have my mind clear on the question, I took my tricycle just as it was after I had left the Paris-Amsterdam race ; and, accompanied by a capable companion, I steered it to a lonely part of the Bois de Boulogne. There, in the forest, I chose a great tree with low-hanging limbs. From two of them we suspended the motor-tricycle by three ropes. When we had well established the suspension, my companion aided me to climb up and seat myself on the tricycle saddle. I was as in a swing. In a moment I would start the motor and learn something of my future success or failure.
Would the vibration of the explosive engine shake me back and forth, strain at the ropes until it had unequalised their tension, and then break them one by one? Would it jar the interior air-balloon's pump and derange the big balloon's valves? Would it continually jerk and pull at the silk hems and the thin rods which were to hold my basket to the balloon? Free from the steadying influence of the solid ground, would the jumping motor jar itself until it broke? and, breaking, might it not explode?
All this and more had been predicted by the professional aeronauts; and I had as yet no proof outside of reasoning that they might not be right on this or that topic.
I started the motor. I felt no particular vibration ; and I was certainly not being shaken. I increased the speed—and felt less vibration! There could be no doubt about it: there was less vibration in this light-weight basket hanging in the air than I had regularly felt while travelling by its means on the tricycle. It was my first triumph in the air !
I will say frankly that, as I rose in the air on my first trip, I had no fear of fire. What I feared was that the balloon might burst by reason of its interior pressure. I still fear it. Before going up I had minutely tried the valves. I still try them minutely before each of my trips.
The danger, of course, was that the valves might not work adequately, in which case the expanding of the gas as the balloon rose would cause the dreaded explosion. Here is the great difference between spherical and dirigible balloons. The spherical balloon is always open. When it is taut with gas it is shaped like an apple ; when it has lost part of its gas, it takes the shape of a pear : but in each case there is a great hole in the bottom of the spherical balloon--where the stem of the apple or the pear would be—and it is through this hole that the gas has opportunity to ease itself in the constant alternations of condensation and dilatation. Having such a free vent, the spherical
