Professor A. Lawrence Rotch h.'91 delivered an illustrated lecture on "Aerial Navigation" in the Living Room of the Union last night. A large audience enjoyed his talk and the interesting views of balloons and aeroplanes which were shown. Professor Rotch prophesied the success of the aeroplane over the dirigible balloon as a means of aerial navigation in the future.

The ocean of the air has certain analogies to the ocean of water, but its navigation is more difficult on account of the instability of the atmosphere. The wind, temperature and humidity have been measured, but the wind currents are of special interest to aerial navigators. The wind currents differ greatly with the time of day and the height. Observations are made by sending up a rubber balloon which carries a basket containing instruments. As the balloon rises the hydrogen expands it until the balloon bursts, when the instruments fall to the ground. A height of eleven miles has been reached in this manner, a temperature of 111 degrees below zero, and a wind velocity of 101 miles an hour.

The speaker then gave a short history of aeronautics. The first ascension was made in 1783 from Versailles, France, in a hot-air balloon. Animals only were sent up, but when it was found to be safe men attempted an ascension. In the same year hydrogen was used as a lifting power. The next year a balloon was first used for scientific purposes, and about the same time one crossed the English channel from England to France. From then on, numberless ascents have been made, and great heights reached.

The dirigible balloon--one answering the helm--was an idea from the very first, yet all attempts to steer a balloon were practically unsuccessful until 1884. Since then many types have been invented, all having the general shape of a fish, the most notable of which is that invented by Zeppelin. They have been brought to a great degree of perfection but have the one great fault that they are practically useless in a high wind.

From the very beginning the aim of inventors has been to arise in a machine which is heavier than air. There were two kinds of these machines, one like a bird, with wings to flap, and the other like a kite. The former has turned out to be worthless, but the latter has been developed into the aeroplane. The first attempt to fly in one of these machines was made in 1894 with little success. Not until almost the beginning of this century when Langley, Chanute, and the Wright brothers turned their attention to this invention was anything like success attained. The flying machine was the outcome of experiments in gliding. The Wright brothers made many trials in this way, and in 1903 applied a motor to their machine. Since then no essential change has been made in their invention, a very remarkable fact.

In closing, Professor Rotch said that it was not safe to prophesy as to the future, but this might be said, that neither the dirigible balloon nor the aeroplane will ever supplant our present means of transportation.