DIALING. 441 



If a thin plate be put within the tube so as to de- 

 cline, or incline, or recline, by any given number of 

 degrees ; and right lines be drawn from its center to the 

 hour-lines of the tube ; these right lines will be the hour- 

 lines of a declining, inclining, or reclining dial, answer- 

 ing to the like number of degrees, for the latitude to 

 which the tube is elevated. 



And thus, by this simple machine, all the principles 

 of dialing are made very plain and evident to the 

 sight. And the axis of the tube (which is parallel to 

 the axis of the world in every latitude to which it is 

 elevated) is the stile or gnomon for all the different 

 kinds of sun-dials. 



And lastly, if the axis of the tube be drawn out, with 

 the plates A D, e f, andg C upon it; and set it up in 

 sun-shine, in the same position as they were in the tube ; 

 you will have an equinoctial dial A D, a horizontal 

 dialey, and a vertical south dial g C; on all which, 

 the time of the day will be shown by the shadow of the 

 axis or gnomon E F G. 



Let us now suppose that, instead of a glass tube, 

 A B C D is a cylinder of wood ; on which the 24 pa- 

 rallel hour lines are drawn all around, at equal distances 

 from each other; and that, from the points at top, where 

 these lines end, right lines are drawn toward the center, 

 on the flat surface A D: these right lines will be the 

 hour-lines on an equinoctial dial, for the latitude of the 

 place to which the cylinder is elevated above the hori- 

 zontal foot or pedestal //; and they are equidistant from 

 each other, as in Fig. 2. which is a full view of the flat 

 surface or top A D of the cylinder, seen obliquely in 

 Fig. 1. And the axis of the cylinder (which is a straight 

 wire E F G all down its middle) is the stile or gnomon ; 

 which is perpendicular to the plane of the equinoctial 

 dial, as the earth's axis is perpendicular to the plane of 

 the equator 



