Most of the automobiles, as everybody is aware, are propelled by gasoline engines. This is not their least wonderful feature. To the ordinary observer it seems quite incredible that a little whiff of air mixed with the fumes of a few drops of gasoline should produce a power that can drive pistons with such force as to throw forward what is virtually a bullet weighing more than a ton.
The power that propels this amazing projectile consisted in the aggregate of a few cubic feet of gaseous vapors. The forward motion of the piston sucked a whiff of the gasoline vapor and air into the cylinder; the backward motion of the piston compressed this gas; an electric spark ignited it; the heat of the electric spark enabled the gasoline molecules to unite with the oxygen molecules with explosive suddenness; the conflagration thus started spread instantly to other parts of the compressed gas; the myriad particles of the gas rebounding from one another at inconceivable speed, pressed with the aggregate power of multitudes upon the cylinder, and drove it back with terrific force; then an escape valve opened; the return thrust of the piston drove out the exploded gas, and one revolution of the engine was complete.
Over and over again this cycle was repeated; each revolution requiring for its performance but a bare fraction of the time required to describe it. The thing is simple enough in practice, but it is a marvelous mechanism when you stop to think of it. That such power should be latent in a seemingly harmless whiff of gas is one of Nature's miracles. And that man should have constructed an engine so nicely adjusted in all its parts as to utilize this power is little less than a miracle of mechanics.
A word should be said about another interesting mechanism that pertains not indeed to the speed of the automobile, but to an accurate record of that speed. That is an electrical timing-device with which absolute accuracy of timing is assured. A moment's reflection will show that it would be quite impossible to time the automobile moving at record speed by the old stop-watch method. The nervous impulse through which the mandate of the brain is conveyed to the hand, and thus made to operate on the stop-watch, travels along the nerve of the arm at the rate of not much more than a hundred feet a second. The delay thus involved, added to the time required for the brain itself to act on the message from the eye, is distinctly appreciable, and every one is aware that individuals differ as to their reaction time.
The practical result, therefore, is that timers are often at variance to the extent of as much as two-fifths of a second. Now in two-fifths of a second, as we have seen, the record motor car covers a distance of over 77 feet. Obviously such latitude in measurement could not be permitted. Hence an electric device has been elaborated which tests the speed with absolute accuracy, recording it automatically on a strip of tape. Therefore the fractional seconds are now stated in hundredths instead of in mere quarters or fifths, and we may be confident—as we could not always be regarding the old-time records—that the different fractions of a second represent an actual difference of speed.
It may be of interest to make a further comparison between the speed of the record automobile and the fastest speed ever attained by a railway locomotive—namely, a mile in thirty seconds. The gap is by no means an insignificant one. A mile in thirty seconds means 176 feet a second. This would allow the champion automobile a lead of over seventeen feet each second; and at the end of a mile the locomotive would be distanced by 1040 feet. It is interesting to visualize the procession that the automobile would leave behind if placed in competition with the various kinds of champions whose feats have been mentioned. As the automobile crossed the line the locomotive would be almost one-fifth of a mile in the rear; 1,900 feet farther back would come the homing pigeon; after a long gap Salvator, the first runner, would come straggling along, having covered little more than one-fourth of a mile; Lou Dillon would be just beyond her first fifth of a mile; the fastest cyclist would be placed between the racer and the trotter; while Hutchins, the swiftest runner at the distance, would have gone only 240 yards from the tape.
For distances greater than two miles, the locomotive record has not as yet been surpassed by the automobile. A locomotive on the Plant system, for example, is credited with a run of five miles in two and one-half minutes (in 1901). But, of course, there is nothing except the mere matter of speed that makes the locomotive engineer's performance comparable to that of the chauffeur. The engineer is driving a machine that runs on a fixed track. He has to do little more than keep up steam and open the throttle. The chauffeur must pick his course, for at any moment a soft spot in the sand may tend to deflect him. How appalling may be the result of a slight deflection with a machine going at great speed has been illustrated by the tragic accidents that have marred the success of many important racing-events, and have led to the oft-repeated question as to whether, after all, such speed tests are worth while. It is a question that everyone must answer for himself. The dangers are obvious; but, on the other hand, most athletic competitions have an element of danger; and enthusiasts may well contend that speed tests make for progress, and are largely responsible for the great mechanical improvement that is in evidence.