64 PHILOSOPHICAJ. THANSACTIOX8. [aKNO IJSO. 



therefore will form a s^ment of a conical surface, still touching the globe in 

 the parallel of lO degrees of latitude. The axis of this cone will coincide with 

 the prolonged axis of the globe, and the side of the cone, which is to be esti- 

 mated from the vertex to the circle of contact, will be the co-tangent of the 

 latitude, or the tangent of 80 degrees. Now this portion of a conical surface 

 may easily be conceived to be unrolled, or to be expanded into a plane surface, 

 without undergoing any other alteration, and then it will become a portion of 

 a sector of a circle ; which portion will have for its length, or middle line, an 

 arch of a circle described with the said tangent, as a radius, whose length will 

 be the same as the parallel of contact, and its breadth will be equal to an arch 

 of the equator of lO d^rees, as before. This s^ment of a sector of a circle, 

 so produced, may therefore be easily described in piano, and within it may be 

 inserted all the places belonging to it, according to their longitude and latitude. 

 Then it must be applied to the globle, so as that its middle line shall coincide 

 with the parallel of JO d^rees; then by pressing it may be bent to the surface 

 of the globe, every meridian to its respective representative, by which it will 

 imiformly contract a little according to longitude, but not at all according to 

 latitude. And thus the globe will be covered as ^r as 15 d^rees of latitude. 



The next zone, or that belonging to the parallel of 20 degrees, may be thus 

 constructed a priori. On a plain paper, with radius equal to the tangent of JO 

 degrees, describe an arch, whose length is equal to that of the parallel of 20 

 d^ees; as also two other concentric arches on each side, at a distance from 

 the middle arch equal to an arch of 5 degrees. This will be the required s^- 

 ment of the circular sector, in which are to be inserted all the places belonging 

 to it, according to their longitude and latitude. Then the middle line or arch 

 is to be applied to tlie parallel of 20 d^rees on the globe, and the segment of 

 the conic^ surface thence arising, is to be duly contracted as before, or pressed 

 close to the globe ; by which means this zone will also be completed. And in 

 the same manner we are to proceed to the succeeding zones, till the whole globe 

 is covered. And the method will not differ in any material circumstance, if 

 instead of a whole globe, we are to construct any part of it only, or what is 

 here called a spherical map. 



^ Copy of an anderu Chirograph, or Conveyance of Part of a Sepulchre, cut 

 in Marble, lately brought from Rome, with sotne Observations on ii by Roger 

 Gale, Esq. r. P. S. N»44l, p. 211. 



Tliis marble lately arrived from Rome, and dqxjsited in the noble museum of 

 Sir Hans Sloane, is a most valuable piece of antiquity, exhibiting a complete 

 formula of a chirograph, or conveyance of one part of a burying-place from one 



