A SIMPLE GLOBE. 561 



The ingenious inventor, who wished to make a clock of his apparatus, 

 and not being able to change its place on the earth from day to day as the 

 time changed, very cleverly reproduced the sun's movement of declination 

 by making it describe a double cone at the axis of the globe. At the 

 equinoxes the poles are in a plane, and equal day and night are shown. At 

 the winter solstice the north pole is inclined backwards at an angle 23 28', 

 and our hemisphere is in the winter season. We have then only eight 

 hours' daylight and sixteen of darkness ; six months later the pole is 

 inclined towards the sun, and the southern pole is plunged in darkness. 

 We have the long days and the southerners the long nights. An upright 

 dial shows the time of the country in which the globe may happen to be, 

 and one can ascertain at any moment what time it is anywhere else. A 

 horizontal dial indicates the day of the month, and changes every day in 

 a manner corresponding with the movement of the earth around the sun, 

 reproduced by means of the arrangement with the double cone. The spectator 

 is supposed to be turning his back to the sun. 



We may add that these movements are all self-acting, and there is 

 no need to interfere with the clock, which is wound up like ordinary time- 

 pieces. By an ingenious forethought the inventor provided that the sphere 

 should be independent of the other movements, and it can be used for 

 demonstration in the hands of the lecturer, and be explained with all its 

 motions without in any way disarranging the clock-work. The globe must, 

 of course, when replaced, be put exactly at the correct day and hour. 



A SIMPLE TERRESTRIAL GLOBE. 



A terrestrial globe without any mechanism, so long as its axis is 

 parallel to that of the earth, exposed to the direct rays of tJie sun, represents 

 our planet with its recurrence of day and night. 



The figure (634) shows us a globe without any support. The axis is 

 north and south, and makes, with the horizon, an angle equal to the latitude 

 of Paris, if the support, AB, be horizontal. To make the axis of the globe 

 parallel to the axis of our earth, the line, NS, must correspond to the 

 meridian of the place ; this can be done with the compass, for instance. 



The solar rays always illuminate one-half of a sphere, no matter what 

 its dimensions. If we look at the illustration we shall see that the line of 

 separation between the light and dark portions of the globe corresponds 

 with that in our earth. This globe, then, tells us the passage of light and 

 darkness for the day, and even for the moment of the day, when it is 

 turned as the earth moves. The place examined should be placed in the 

 meridian of that place (Paris, for instance), and occupy the most elevated 

 spot on the globe. The earth is then in just the same position, and 

 daylight and darkness are shown exactly as they exist on the earth at 

 the time. 



If this globe be then observed for a few minutes, the sun will be seen 



36 



