THE CONQUEST OF TIME AND SPACE 



The original log was so called because it consisted 

 essentially of an actual log or piece of wood. To the 

 center of this a string was attached, and in testing the 

 ship's rate of progress this string was allowed to slip 

 through the fingers of a sailor who counted the number 

 of knots— placed, of course, at regular intervals on 

 the string— that passed through his fingers in a given 

 time. As the log itself would remain practically station-4 

 ary in the water where it was dropped, the number of | 

 knots counted indicated the distance traversed by the 

 ship in a given time. In practice the time was usually 

 gauged by a half-minute sand glass, and the knots were 

 arranged at such a distance on the cord that, in the 

 course of the half minute, one knot would pass through 

 the fingers for each nautical mile covered by the ship 

 in an hour. The actual distance between the knots was 

 therefore about fifty feet. The nautical or geographical 

 mile represents one degree of the earth's circumference 

 at the equator, amounting therefore to 6,008 feet, 

 as against the 5,280 feet of the statute mile. It was 

 the use of the log-line with its knots, as just explained, 

 that led to the dubbing of the nautical mile by the name 

 "knot," which is still familiarly employed, though the 

 knotted log-line itself has been superseded in recent 

 times, except on very old-fashioned sailing ships. 



The log retains its place even in the most modem 

 ship, though its form is materially altered, and its im- 

 portance is somewhat lessened owing to the fact that 

 the experienced skipper can test the speed of his ship 

 very accurately by noting the number of revolutions 

 per minute of the ship's propellers. It is indeed the 



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