Geographical and Topographical Improvemenis. 253 



>.he angle of altitude, the angle of declivitv, and perpendi- 

 cular height of every hill ; likewise the comparative height 

 of different hills, the best route by which the high grounds 

 may be gradually ascended, and where heavy burthens can 

 be drawn up with most ease. 



2dly. Experience has sufficiently shown that the inhabi-. 

 tants of low grounds are sul:jject to different kinds of sick- 

 ness, from which those living at places elevated to a certaia 

 degree are exempt. A map on this improved plan will point 

 out the most proper situation for building dwellimr-houses. 

 It will be useful in botany, in discovering or cultivalino- 

 some kinds of plants which flourish best at particular di- 

 stances above the level of the ocean. It will trace the line 

 of vegetation on the sides of lofty mountains whose tops 

 are covered with eternal snow. 



Sdly. Some high lands are known to produce good grain, 

 while low lands afford grass more abundautlv"; but most 

 grounds produce good grass over which a moderate quan- 

 tity of running water is conveyed. A plan of any country 

 in this way will show all the ground that can be irrigated ; 

 where water-works may be erected j where navioable'canals 

 may be cut ; and where highways and rail-roads mav be 

 laid out on the best and most level ground. 



4thly. The subterraneous treasures of the mineral and 

 fossil liingdcmis are generally found in strata ; and, if they 

 arc not truly horizontal, they make a certain ano;Ie with 

 the horizon. A map on this projection may enable the 

 mineralogist to follow any one stratum at places even far 

 distant from each other. 



PUOI3LEM. 



To find the true declivity of any piece of ground in any 

 map laid down on the principles of the present plan. 

 E raw pie \sl, far D. See Plate FI. 

 As the perpendicular height, 4 feet - 60206 



Is to radius, 90" - - - lOOOOOO 



■ So is the horiiiontal distance, 4 feet - 60206 



10-60206 

 Tothc co-tangv;nt of the declivitv, 4.>° - 10*00000 



llxiimple '2d, for B, 



As the perpendicular height, 4 feet - 60206 



Is to raduis, 90'' - - - lO-OOO(K) 



So is the horizontal distance, S feet - 90309 



I0-yo300 

 To the CO -tangent of the declivity, 20 34' 10-30U)J 



JLlxumple 



