‘ON THE ANTIQUE HOUR-LINES. 79 
» Explanation of the Figures. 
Central Projection of the Twelve Hour-lines, Figure ist do 
Figure 3d. 
Figure. 1st, Is a central or gnomonic projection of the hecte- 
morial lines or antique hour-lines, on the inside of a plane 
touching the sphere at the elevated pole of the equator. 
This and all the other figures are drawn for the latitude 
66° 30. Each antique hour-line is marked with the Greek 
numeral that belongs to it, 
Figure 2d, Is a central projection of the summer Ne se of these 
lines on the inside of a plane touching the apbere at the 
depressed pole of the equator. 
The circle placed between figure Ist and figure 2d is a 
great circle of that sphere from which all the projections 
jap these. figures (except figure 9th) are formed. 
Figure 3d, Is a central projection of the hectemorial lines on a 
.. plane touching the sphere at the depressed intersection of 
the meridian and the equator. 
yo Be of 1 the five undulated Cones which contain the antique 
hour. lines, by a plane at right angles to the avis, figure 4th 
‘to figure 8th. 
Figure 4th, Is a section at right sie to the axis of the un- 
dulated conical surface, which contains the first antique 
»hour-line A, and eleventh 1A. In this and the other fi- 
gures, the full lines are the section of one of the two op- 
posite cones, and the dotted lines are the section of the 
other. 
