UO^ GEOGRAPHICAL AND TOPOGRAPHICAL IMPROVEMENTS. 



Ibe level ; or, in other worcjs, it will bend towards the centre 

 qf the ifland. Hence, by a little practice, the fliape of the 

 feveral horizontal lines on the map will give as clear an idea to 

 the mind, of the fliape of any country over which they paf^, 

 as a fight of the country itfeif can convey to the eye. But to 

 obtain a mathematical and true knowledge of the altitude and 

 declivity of any part of the country, we have the following 

 proportion : 

 Trigonometrical As the perpendicular l>eight of any one horizontal line above 

 ruje for the de- another is to the radius: fo is the horizontal diflance between 

 the horizontal lines meafured on the map at any particular 

 place : to tlie co-langent of declivity at that place. 



.V«fe.— If the horizontal diftance between any two horizon- 

 tal lines on the map is equal to the perpendicular height of 

 any horizontal line above another, the angle of altitude, or 

 declivity, of any hill will be 45 degrees, 

 Advantagcsj The prefent improvement, which I believe to be entirely 



new, will be found to pofifefs the following advantages : 

 —to military ift- Military men are well acquainted with the many ad- 



'"^"> vantages always to be gained from the exa£l reprefentalion of 



high grounds. By this method, we are able to give the angle 

 of altitude, the angle of declivity, and perpendicular height 

 of every hill; likewife the comparative height of different 

 hills, the beft route by which the high grounds may be gradu- 

 ally afcended, and where heavy burthens can be drawn pp 

 with moft eafe. 

 «— and fordomcf- 2dly. Experience has fufficiently fliown, that the inhabitants 

 tic and econo- ^j- j^^^ grounds are fubiecl to different kinds of ficknefs, from 

 jnical purpofes, , . , , r i- • i i i • , 



which thole livmg at places elevated to a certain degree are 



exempt. A map on this improved plan will point out (he 



mod proper filuation for building dvvelling-houfes. It will be 



4ifeful in botany, in difcovering or cultivating fome kinds of 



plants which fiourifli beft at particular diftances above the 



level of the ocean. It will trace (he line of vegetation on 



the (ides of lofty mountains, whofe tops are covered with 



eternal fnow. 



— rto dire<a agri- Sdly. Some high lands are known to produce good grain, 



colturalimprove- ^^j|g i^y^ ja^^jg afford grafs more abundantly; but moft 



mtnts, 1 1 r 1-1 1 



grounds produce good gral«, over which a moderate quantity 



of running water is conveyed. A plan of any country in this 

 way will fliow all the ground that can be irrigated ; where 



water- 



