CHAP. IV.] ADOLESCENCE 1844 TO 1847. 



89 



[1847.} 



I have made a map of the world, conical projection 



ACD is the one cone, BCD the other ; the side AC = dia- 

 meter of the base CD ; therefore, when unrolled, they are 

 each semicircles. 



To make the map take OD = OD and OA = f of 

 OD, and describe a circle from 0, with radius OA ; this is 

 the circle of contact. Let the longitude of a point P= 60 ; 

 take AOC in the map = 30; let its latitude be 65; 

 subtract 30, and take the tangent of 35, make AB = 

 tangent. B is the point. 



