Page:My Airships.djvu/259

 and there was nothing to show that the force of the wind going and coming was constant. It is true that on those flights one of the difficulties standing in the way of such speed calculations—the "shoot the chutes" (montagnes Russes) of ever-varying altitude—was done away with by the operation of the maritime guide rope; but, on the other hand, as has been said, the dragging of the guide rope's weight through the water acted as a very effectual brake. As the speed of the air-ship is increased this brake-like action of the guide rope (like that of the resistance of the atmosphere itself) grows, not in proportion to the speed, but in proportion to the square of it.

On those flights along the Mediterranean coast the easy navigation afforded me by the maritime guide rope was purchased, as nearly as I could calculate, by the sacrifice of about 7 or 8 kilometres (4 or 5 miles) per hour of speed; but with or without maritime guide rope the speed calculation has its own almost insurmountable difficulties.

From Monte Carlo to Cap Martin at 10 o'clock of a given morning may be quite a different trip from Monte Carlo to Cap Martin at noon of the same day; while from Cap Martin to Monte