LESSONS IN GEOGRAPHY. 



near itn low y A, draw D of indefinite length, and at 



rih'lit represents the point through 



whu-li tin- p.iruil.-! ..f 51* 30' would pass if it were traced in th.< 

 ,, i ,.j. .!,,,!,. A - -nine a space equal to 60 geographical miles, or 



t>n.- .1. .'!. t tii- , ,,u uor (in Fig. 21 we hare aMumed this as 



being oqual to an inch) ; sot off half tho length of this space np- 

 wanl* I'l.-in , and uiuiilior the point thus obtained 

 in A u as 55, and from 55 set off four . f the apaOM 

 assumed, numbering the points thus obtained, 56, 

 57, 58, and 59. From 59 sot off to F a space 

 equal to that set off from to 55. Now we will 

 take the parallels of 59 and 55 north latitude as 

 the parallel* through which the circumscribing cone 

 would out the sphere if we were going to work 

 to construct r, projection of the conical form as for 

 Hi.- map of Europe, and through the points thus 

 numbered draw short straight lines parallel to DB, 

 iin.l ulno through 

 T a straight line 

 i; ic, parallel to 

 DE. The straight 

 line a H forms 

 the northern 

 limit of our map. 

 It is now neces- 

 sary to construct 

 a diagonal scale 

 on the space as- 

 sumed as equal 

 to one degree of 

 the equator, aa 

 in Fig. 21, to 

 enable us to de- 

 termine propor- 

 tionately the 

 length of a de- 

 gree of longitude 

 under the paral- 

 lels 59 and 55. 

 On referring to 

 the table given 

 inVol.II.,p.357, 

 we find that a 

 degree of longi- 

 tude is equal to 

 34'41 geographi- 

 cal miles under 

 thc55th parallel, 

 and to 30-90 geo- 

 graphical miles 

 under the 59th 

 parallel. These 

 are represented 

 respectively by 

 the straight lines 

 a b, c d in the 

 diagonal scale. 

 Now along the 

 straight line 

 drawn through 

 the point 55, 

 which we will 

 call e, set off e g, 

 eh, on either [ 

 side of AB, each ~" 

 equal to half a /., 



and along the ,, 



line drawn 

 through the 



p->int 59, or /, set off fk, fl, each equal to half c d, and join 

 kg, lh; the four-sided figure, kg hi, thus formed is the pro- 

 jection of half a degree of latitude on each side of the straight 

 line A B, which represents the 4th meridian west from Green- 

 wich. To extend this on either side, extend the compasses 

 from k to h, or from I to g ; and with the radius thus obtained, 

 from the centre c strike the arc m n, and from / as centre 

 strike the arc o p ; then from e as centre, with a radius equal 

 to ab or g h, draw arcs intersecting the arc o p in o and p ; and 



from / M centre, with radio* equal to cd or ft I, 

 cutting the wo * in m and n. Join MO. j>. prodoesar 

 them, M far M aeoaeaary, till they meet UM straight line* D t. 

 OH. The straight line* mo, up Ttyrmmt respectively UM 

 meridian, of 5 and 3 west from Greenwich. W thae 

 obUin a projection for OM degree on either aide of A a. 



The projection most be Bnntiasxd M far w 



n 7 on either aide of AB bjr repeating the 



process that i* to aay, from MM* eeatre, with 

 radius m , an arc moat b* truck passing throejgn 

 the point* e and , the point being fixed by 

 drawing an arc from o u centre, with radio* o ot 

 ab. Similarly from o u centre, with ewe nsj* 

 namely, a radios equivalent to a diagonal of ma 

 of the three quadrilateral ftgores mot/, kg 1 1. 



or fepn draw an arc 



throagh/aad 



this last point q being fixed in position by inter- 



eeting the are 



r 1 tort drawn by 

 _. H another de- 

 scribed from m 

 a* centre, with 

 a radio* mf or 

 e d. Join q i, 

 and produce it 

 till it meets the 

 straight line* 

 OH, D B, the 

 lin.it, of th. M| 

 on the north and 

 sooth. This re- 

 present* the 6th 

 meridian of west 

 longitude. The 

 pairs of point* 

 v *, r t, y, 

 through which 

 the meridian* 

 numbered 7, 2, 

 and 1 are drawn 

 respectively, 

 must all bo de- 

 termined by a 

 repetition of the 

 same process. 



The parallel* 

 of 59 and 55 

 north latitude, 

 or rather the 

 fine* that repre- 

 sent them, may 

 now be formed 

 by joining the 

 point* , o, m,/, 

 , r, r for the 

 former, and x, t, 

 o, ', r, '. y for 

 the latter, ruling 

 short straight 



hi..-- ': !:. ; .].' 



to point These 

 lines may be 

 extended as far 

 as requisite eart 

 and west by 

 drawing faintly 

 an extra men 

 dian on either 

 aide beyond UM 



border of tho map, by the process already described for the 

 others. The lines war, qt, mo, np, rt, and r y must t 

 divided into four equal spaces like tf, and the i-a- 

 57, and 56 traced by joining the points of division by ruling 

 short straight lines from one to the other, as iu the case of the 

 parallels of 59 and 55. 



Nothing now remains bnt to complete the border and number 

 the parallels and meridians, a* in the projection of the map 

 of Europe in VoL IL, p. 356. A suitable space should also be 



