THE USE OF THE ARMILLARY SPHERE. 337 



fitted to shew either the real motion of the earth, or the LECT 

 apparent motion of the heaven. 



To rectify the sphere for use, first slacken the screw 

 r in the upright stem R, and taking hold of the arm 

 Q, move it up or down until the given degree of latitude 

 for any place be at the side of the stem R ; and then the 

 axis of the sphere will be properly elevated, so as to 

 stand parallel to the axis of the world, if the machine 

 be set north and south by a small compass : this done, 

 count the latitude from the north-pole, upon the celes- 

 tial meridian L L, down towards the north notch of the 

 horizon, and set the horizon to that latitude ; then, turn 

 the nut b until the sun Y comes to the given day of the 

 year in the ecliptic, and the sun will be at its proper 

 place for that day : find the place of the moon's ascend- 

 ing node, and also the place of the moon, by an Ephe- 

 meris, and set them right accordingly : lastly, turn the 

 winch W, until either the sun comes to the meridian 

 L L, or until the meridian comes to the sun (according 

 as you want the sphere or earth to move) and set the 

 hour-index to the Xlt, marked noon, and the whole 



machine will be rectified. Then turn the winch, and 



observe when the sun or moon rise and set in the hori- 

 zon, and the hour-index will shew the times thereof for 

 the given day. 



As those who understand the use of the globes will 

 be at no loss to work any other problems by this sphere, 

 it is needless to enlarge any further upon it. 1 ** 



Note 102. An admirable apparatus of this description has been 

 constructed by Messrs. Jones of Holboic. 



22. 



