| SPEED OF WIND | PRESSURE | SPEED OF WIND | PRESSURE | ||||||||||||
| 5 | Miles | per | hour | 2 | oz. | 35 | miles | per | hour | 6 | lb. | 2 | oz. | ||
| 10 | “ | “ | 88 | “ | 40 | “ | “ | 8 | “ | ||||||
| 15 | “ | “ | 1 | lb. | 2 | “ | 45 | “ | “ | 10 | “ | 2 | “ | ||
| 20 | “ | “ | 2 | “ | “ | 50 | “ | “ | 12 | “ | 2 | “ | |||
| 25 | “ | “ | 3 | “ | 2 | “ | 55 | “ | “ | 15 | “ | 2 | “ | ||
| 30 | “ | “ | 4 | “ | 8 | “ | 60 | “ | “ | 18 | “ | ||||
Varying Degrees of Pressure.—It is curious to notice how the increase in speed changes the pressure against the blade. Thus, a wind blowing 20 miles an hour shows 2 pounds pressure; whereas a wind twice that velocity, or 40 miles an hour, shows a pressure of 8 pounds, which is four times greater than at 20 miles.
It differs, therefore, from the law with respect to water pressure, which is constant in relation to the height or the head—that is, for every 28 inches height of water a pound pressure is added.
Power from Waves and Tides.—Many attempts have been made to harness the waves and the tide and some of them have been successful. This effort has been directed to the work of converting the oscillations of the waves into a rotary motion, and also to take advantage of the to-and-fro movement of the tidal flow. There is a great field in this direction for the ingenious boy.
A Profitable Field.—In no direction of human[p. 138] enterprise is there such a wide and profitable field for work, as in the generation of power. It is constantly growing in prominence, and calls for the exercise of the skill of the engineer and the ingenuity of the mechanic. Efficiency and economy are the two great watchwords, and this is what the world is striving for. Success will come to him who can contribute to it in the smallest degree.
Capital is not looking for men who can cheapen the production of an article 50 per cent., but 1 per cent. The commercial world does not expect an article to be 100 per cent, better. Five per cent. would be an inducement for business