DIALING. 73 



to the figure, page 71, it will not be difficult to perceive that if the 

 circle C H A, had been the equator,. then all the angles of the 

 hour lines D A, D I, D II, &c., would have been measured by 

 equal arcs, each 15. The same would 'be true of any small 

 circle, I K, parallel to the equator* the meridians, 15 apart, would 

 divide it into 24 equal parts. Now, if on a globe, we should 

 divide any parallel of latitude, such as I K, before alluded to, into 

 24 equal parts, and then pass a plane, a sheet of paper for example, 

 through each of these divisions and the centre of the globe, then, 

 wherever this plane intersected the plane of any other circle, C 

 H A for example, it would mark out the directions of the hour 

 lines D A, D I, D II, D III. &c. Take, BOW, a flat board, on 

 which a sheet of paper is fastened, and describe a circle whose 

 centre is O, as in the diagram below, and let O B be a metallic 



rod, inclined to the line A C, drawn on the paper to represent a 

 meridian line, at an angle equal to the latitude of the place, let 

 D E be a small circle, so fixed on O B, that its plane is everywhere 

 perpendicular to it, or in other words, so that the distance from 

 the point B to the circumference of the circle, may be the same 

 throughout. Let this smaller circle be graduated into 24 equal 

 parts, and subdivided into halves, and quarters, and if desired, 

 still smaller spaces. Take, now, a fine thread, or a straight edge, 

 and carry it from B through each division of the little circle, 

 successively, down to the plane of the paper below, taking care, if 

 a thread is used, not to crooR it against the edge of the little circle, 

 but simply passing it straight down. Through the points F, G, H, 



