Ferber advised Blériot to adopt an elevating rudder also, because the effect produced by changing the position of the center of gravity, although efficacious is very difficult and delicate to control.
The conclusion of an article by Ferber in “Nature” of August 10, is worthy of note. He says: “Let us remark, in conclusion, how fruitful is the method of personal trial which we have always advised in preference to any calculation. This year, with his fourth apparatus, Blériot has not met with any damage to his aeroplane. He made the trials himself and they quickly led to results, because each trial gave him an exact idea of what was to be corrected. That is the condition of success.”
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APPENDIX
STUDY OF THE AMERICAN BUZZARD AND THE “JOHN CROW”
In the preparation of this Memoir, the writer has deemed it best to generally omit any mention of plans and ideas which were brought forth in the work, unless constructions or tests in accordance with them were carried to a sufficient extent to admit of some definite conclusion regarding them. However, owing to the important part played by the warping of the supporting surfaces, or the variation in the angle of auxiliary surfaces, in the methods of preserving the equilibrium of practically all flying machines of the present day, it may be of interest to here add a short mention of the direction in which plans along this line were originally proposed in this work. Mention has already been made of the importance which Mr. Langley attached to the study of the works of the great master-builder, Nature, though recognizing at the same time that owing both to the difference in the forces and methods of construction possible to man, it was not in general possible for him to produce the best results by attempting to too closely imitate the methods or plans of Nature.
Mr. Langley considered it not practicable or best to attempt to imitate the details of construction of the flying mechanism of birds. At the same time, he strongly believed that much was to be learned from them about the practical side of the art of balancing, and he therefore spent a great deal of time both in analyzing the methods practiced by the birds in preserving their equilibrium and in criticizing his own plans in this direction in the light of what Nature would seem likely to do if she had to construct a flying creature on such a large scale. In carrying on his investigations in the art as practiced by the birds, he made a trip to Jamaica during the early weeks of 1900, in order to study the species of buzzard which are so numerous and tame there and are known locally as the “John Crow.” After his return from this trip he wrote the following very interesting letter to Mr. Robert Ridgway, requesting certain data regarding the American buzzard, which he wished to compare with some data on the “John Crow” which he had obtained on this trip:
MARCH 29, 1900.
DEAR MR. RIDGWAY:
I have just returned from Jamaica, where among other occupations, I have been studying the evolutions of the buzzard locally called the “John Crow,” a soaring bird which is almost as much superior in skill to our buzzard as that is to a barn-yard fowl in its power of keeping itself in the air without flapping its wings, in what is very nearly a calm.