170 Mr. J. Y. Buchanan on the Use of the Globe 



After laying down the great circles Nos. 0, 1,2, 3, 4, and 5, 

 representing the fundamental face No. and the five neigh- 

 bouring ones, which by their intersections make No. a 

 pentagon, the positions and inclinations of faces and edges 

 were taken off with the metrosphere. The measurements are 

 along great circle No. from one of iits intersections with 

 No. 1 as 0° of azimuth, and altitudes above or below it. 



No. of face or great circle . . . 

 Azimuth of node 



1 



0° 

 53° 



2 

 102° 



3 



154° 



654° 



4 



209° 

 66° 



5 



282° 

 06° 



Greatest altitude 





These are laid down directly from the data supplied for the 

 crystal, and the small differences of the values thus found on 

 the globe from those intended to be placed on it will give an 

 idea of the precision to be obtained with the particular globe 

 and circles. In the following table we have values derived 

 graphically from this construction for the position and direc- 

 tion of edges formed by the meeting of any two of the faces 

 represented on the globe b}^ great circles. As before, the 

 edges are represented by their parallel diameters, and these 

 are designated by the nodes in which they meet the sphere. 

 The azimuth and altitude of each of these nodes is given in 

 the table. As the diameters also pass through the centre of 

 the sphere, the edge is specified both as to direction and 

 situation. 



Node No 



Azimuth 



1,2 



288° 

 52° 



2. 3 

 25° 

 61° 



90° 

 03° 



4,5 



156° 



61*° 



5,1 



250° 

 51° 



Altitude 





Altitude 



1,3 



343° 



23|° 



1,4 



109° 

 22° 



2,4 



55° 

 44° 



2,5 



270° 

 24i° 



o, 5 



127° 



43]° 





The first five of these edges actually occur ; the last five 

 are the remaining possible edges which would be formed by 

 the faces produced. They are shown on the globe exactly 

 the same as the others, because, if a number of great circles 

 be drawn on a sphere, every one of them bisects every other. 



In the next table we have the plane angles on face No. 



