Letter from Alexander Graham Bell to Mabel Hubbard Bell, October 25, 1901
Cape Breton, N. S
October 25, 1901.
Dear Mabel: —
Since you left, the kite, or rather the flying machine, has occupied pretty nearly all of my thoughts. I have realized that Prof. Newcomb has done a great service by pointing out the undoubted fact that you cannot increase indefinitely the dimensions of a flying machine upon any given model, because the weight will increase as the cube of the dimensions; whereas the sustaining surfaces increase only as the square of the dimensions. So that the FLYING WEIGHT — that is the ratio of weight to surface — continually increases with the size of your model and large machines, capable of carrying men and engines, &c. would be impracticable because their weights would be too great to be sustained by their surfaces.
I find this is as true of kites as of flying machines
For example, if you construct two kites (A) and (B) upon the same model — one of double the dimensions of the other in every way, — (B) will weigh 8 times as much as (A), but have only four times the supporting surface, so that the flying weight of (B) — that is the ratio of weight to surface — is twice as