24 
number answering to tbe natural sign or tangent of any 
arch, be set off on its respective line from the centre 
towards the left hand, it will give the point answering to 
the sign or tangent of that arch.* 
The line of sines, tangents, and versed sines being thus 
constructed, the line sine of the rhumb, and tangent of the 
rhumb, are easily divided; for if the degrees and minutes 
answering to the angle which every rhumb makes with 
the meridian be transferred from its respective line to that 
which is to be divided, we shall have the several points 
required. 
Example. For instance, if the distance between the 
radius or centre, and the sine of 45° equals the fourth 
rhumb, be set off upon the line sine of the rhumb, we shall 
have the point answering to the sine of the fourth rhumb; 
and after this manner are both these lines constructed. 
The line of meridional parts is constructed from the table 
of meridional parts, in the same manner as the line of num 
bers is from the logarithms.*! 
SECTION IV. 
THE GLOBULAR PROJECTION, EXHIBITING THE GLOBULAR 
CONSTRUCTION OF MAPS. 
49. Problem I. The principle of this projection. If the 
eye be supposed to be removed from the surface of the 
sphere, to a distance equal to the sine of 45° of the cir 
cumscribing or primitive circle, the projection is called 
the globular projection (article 20). 
* Example. Thus, the natural sine of 30° being 5,000, &c., 
if the distance between the centre of the line of numbers, which in 
this case is equal to 10,000, &c., equal the radius; and the division, 
on the same line representing 5,000, &c., be set off from the centre 
or 90°, on the line of sines towards the left hand, it will give the 
point answering to the sine of 30°. 
f This table is given in art. 60, and the principle of its applica 
tion in setting off the distances upon the meridional line is explained 
along with the table.