. The Civil engineer and architect's journal, scientific and railway gazette. Architecture; Civil engineering; Science. •M4 THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. [November, of a s)iip being deternilnpd with the ordinary log, hy ascertaining how much of the line, attached to the log, ran out in a given time, it was essential that hnth the time and the distance should be correctly measured ; but that was seldom tlie case, as the sand in the sanil-glass, which measured the time, was atTected by every change in the atmosphere, and the line which measured the distance was alternately wet and d
. The Civil engineer and architect's journal, scientific and railway gazette. Architecture; Civil engineering; Science. •M4 THE CIVIL ENGINEER AND ARCHITECTS JOURNAL. [November, of a s)iip being deternilnpd with the ordinary log, hy ascertaining how much of the line, attached to the log, ran out in a given time, it was essential that hnth the time and the distance should be correctly measured ; but that was seldom tlie case, as the sand in the sanil-glass, which measured the time, was atTected by every change in the atmosphere, and the line which measured the distance was alternately wet and dry, anil being stretched unequally, at diiVerent parts, it was impossible that the marks, or Unots, could remain at distances winch tliey were intended to indicate. These difficulties, when the vessel was going less than 8 or 9 miles an hour, might be partially surmount- ed, by counting the recpnsite number of beats of a good watch, instead of using tl'.e sand glass, and by actually measuring the quantity of line which ran out, instead of counting the distance by the knots. Cut in heaving the log at higher rates, it was difficult to prevent the log from being dragged after the ship, by the friction of the reel, and whether the line was " taken olT" or " paid out," there was always a degree of doubt, whether the correct length had been allowed to go off the reel. It was also nearly impossible to measure the time to the requisite degree of accuracy, hy the 14 seconds sand glass, which was generally used at high rates. For instance, if a vessel were going 14 kno:s, the quantity of line representing one mile passed through t!te hand of the observer in one second of time ; and hence, in order to ob- tain the speed to the eighth part of a mile, it wo\dd be necessary to measure tlic interval lo the eighth part of a second. In like manner, to obtain a ves- sel's speed to the eighth part of a mile, when she was going lU knots, it would be necessary to measure the i
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