APPARENT TIME. 85 



it to be changing its position scarcely at all, and gives notice to the 

 person with the watch, or chronometer, to be ready; in a moment, 

 instead of rising, as before, it begins to dip below the horizon, 

 and he calls out, and the time is accurately noted. This is the 

 exact instant of 12 o'clock, apparent time, or the instant when the 

 sun, having reached its highest point, begins to decline. Now 

 the chronometer, with which he has been observing, does not say 

 12 o'clock, but perhaps, 3h. 5m. 10s. in the afternoon. We will 

 suppose the observation to be made on the 27th day of August. 

 On this day, as will appear from a table showing the equation of 

 time, a clock adjusted to keep true solar time, should show 12h, 

 1m. 10s. at apparent noon, and this is the time which the clock 

 would show at Greenwich, at apparent noon there upon this day; 

 but when it is apparent noon at the place where we have just 

 supposed an observation made, the Greenwich clock shows 3h. 

 5m. 10s., the difference is 3h. 4m., which, allowing 15 for each 

 hour, indicates that the observation is made in a place 46 west 

 of Greenwich. It is west, because the sun comes to the meridian 

 later than at Greenwich. Now if the latitude was known by ob- 

 serving the altitude of the polar star, then, by referring to a chart, 

 the position, either on ocean or land, where the observation was 

 made, could be indicated; for all charts, or globes, which represent 

 the earth's surface, have lines drawn upon them, through the 

 poles, called meridians, showing every degree east or west of 

 Greenwich, and also every degree north or south of the equator. 

 We will close this somewhat tedious chapter, with an allusion 

 to a circumstance which has sometimes puzzled the uninitiated, 

 viz : two ships may meet at sea and vary in their reckoning a day 

 or two. Suppose a traveler, leaving New York on a certain day, 

 to travel continually east, until after a certain time, one year, 

 or perhaps twenty, he arrives at the place from which he started; 

 and farther, suppose he has kept an accurate note of the number 

 of days which has intervened. For every 15 he has traveled 

 east, the sun has risen one hour earlier to him than to those 

 left behind. This gain, by the time he has traveled 360, amounts 

 to a whole day, and when he arrives home he finds his reckoning 

 one day in advance of his neighbors, or in other words, he has 



