Principles of Aeroplanes Explained

The first of a series of lectures to be given this winter under the auspices of the newly organized Harvard Aeronautical Society was delivered last evening in the Fogg Lecture Room by Mr. A. A. Merrill, lecturer on aeronautics for the Boston Y. M. C. A. His topic was "The Principles of Mechanical Flight" and the lecture was illustrated with excellent views of the Wright, Curtiss and Bleriot machines in mid-air.

Mr. Merrill began his lecture with a brief history of the development of the aeroplane, which is the only practical method of the three employed to elevate a heavier-than-air machine. The other two the use of vertical screws and the oscillation of wings, involve almost insoluble questions of stability. No progress was made in aeroplanes until Langley showed that the estimation of power necessary to lift a given weight was erroneous. Maxim took up the Work of Langley and contrived to lift 8,000 pounds by the proper balancing of horizontal planes. Lielienthal, a German scientist, attacked the problem of stability which had hitherto impeded any practical progress in mechanical aviation. Mr. Merrill then showed stereopticon views of the gliders invented by Lielienthal and explained the two varieties of stability against which the aeronaut has to contend.

Stability is of two kinds: transverse and fore and aft. The aeroplane in mid-air has two forces acting on it besides that of gravity, a tendency to turn over sideways and a tendency to pitch either backward or forward. To counteract the former, and thus gain transverse stability, the Wrights warp the ends of their planes in such a way as to apply a downward force on the elevated side. To minimize the danger of pitching forward and thus gain fore and aft stability, the horizontal rudder, rigged either in front or behind the machine, is the most effective method which has up to the present time been found.

After demonstrating the principles of soaring, by blackboard diagrams, Mr. Merrill went on to explain the present weakness of the aeroplane, namely, the engine. It is the inefficiency of the motive power which has and still does limit the range and speed of the heavier-than-air machine. It is on the engine that French scientists are now putting their greatest efforts. To get the maximum horse-power with a minimum weight is the present problem of aeronautics. If the engine ceases to supply power the aeroplane has to descend and if this happens over a country devoid of suitable landing places the results are bound to be serious.

Mr. Merrill concluded his lecture by quoting at length from a pamphlet by Hiram Maxim, the well-known authority on military aeronautics. Mr. Maxim's opinion is that the development of aerial navigation will lesson the chances of war in that nothing save subterraneous works will be free from the bombs dropped by aeroplanes.

After the lecture Mr. W. H. Aitken, who has charge of the aeronautical exhibit at the "Boston 1915" exposition, gave several demonstrations of the Bleriot aeroplane by the use of a small paper model which was would up and propelled about the lecture hall.