75 spindles with preparation flax yarn. I beg leave here to make the following extract, on the subject of animal force, from Dr. Young's Natural Philosophy, Vol. II. p. 165. "In order to compare the different estimates of the force of moving powers, it will be convenient to take a unit which may be considered as the mean effect of the labour of an active man, working to the greatest possible advantage, and without impediment; this will be found, upon a moderate estimation, sufficient to raise 10 pounds 10 feet in a second for 10 hours in a day; or to raise 100 pounds, which is the weight of 12 wine gallons of water, 1 foot in a second, or 36000 feet in a day, or 3 600 000 pounds, or 432000 gallons, 1 foot in a day; this we may call a force of 1, continued 36000," Explanation of the Table of Wheels in The wheels are all reduced to what may called one denomination. be First-By proportioning their breadths all to what they should be to have the same strength, if the resistance were equal to the work of a steam engine of ten horses' power. Secondly-By supposing their pitch lines all brought to the same velocity of 3 feet per second, and proportioning their breadths accordingly. I have chosen this particular velocity of 3 feet per second, because it is the velocity very common for overshot water wheels. Such cases as appear to have worn too ra pidly, are marked, which may tend to discover the limit in point of breadth. |