50. ON THE ANTIQUE HOUR-LINES. 
other. The section of the same undulated cone by a cy- 
lindrical surface, is seen in figure 10th. 
Figure 5th, Is the right section of the undulated cone whicli 
contains the second antique hour-line B, and tenth I. The 
section, by a cylindrical surface, is seer at figure 11th. 
Figure 6th, Is the right section of the undulated cone which: 
ao 
* contains the third antique hour-line T, and ninth ©. Its 
section, by a cylindrical surface, is figure 12th. A per- 
spective and shaded view of this undulated conical sur- 
face is figure 9. } 
Figure 7th, Is the right section of the undulated cone which: 
contains the fourth antique hour-line A, and the eighth H ;, 
figure 13th is its section by a cylindrical surface. 
Figure 8th, Is the right section of the undulated cone which 
contains the fifth antique hour-line E, and the seventh Z.. 
Figure 14th, is its section by a cylindrical surface. 
Perspective and shaded wiew of one of the Surfaces, figure 9th. 
Figure 9th, Is a perspective and shaded view of the undulated’ 
conical surface which contains the third antique hour-line 
Tr, and ninth ©; the point of sight is in the plane of the: 
equator, and the distance of the eye is two. diameters from. 
the centre of the sphere ; in this view only one of the two. 
opposite surfaces is drawn. The right section of these 
opposite cones is figure 6th, and their section by a cylin- 
drical surface is figure 12th. 
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