I.KSSMNS IN' 



halln, tho upper one being gaUeried ; and the rearrangement of 



urn is being proceeded with a* rapidly a* circumstances 



duo a Botanic Garden in connection with th.< 



tho F'rofoBBor of Botany give* the praotical 



portions of his coarse. 



I.KSSONS IN (JKiHJKAI'HY. XI.III. 



MAP MAKING M EKCATOK'U I'UOJKC I 



We nhall now bring our Lessons on Geography to a close, in this 

 , with a few praotical remarks on map-making 



. tin- iiMni.-tiona that hare been already given in 



n lessons for delineating the continents of Europe, 



N..rth and South America, or any large portion 



Ts surface, the form of projection known as the 



projection being chiefly used. In the present lesson wo 



..n*ilcr tho method of drawing a map of the world, \>y 



means of the rectangular form of projection, called, after its 



r, M creator's Projection, after making a few remarks 



mode of procedure to be adopted in delineating and 



colouring maps of iUl kiml*. 



Tho various mathematical instruments required have been 

 already enumerated at tho commencement of our " Lessons in 

 Geometry," and it will suffice to repeat here that tho draughts- 

 man must in addition to compasses, rulers of various kind-, 

 ruling pens suitable for drawing fine and thick linos, and a T 

 square also provide himself with a beam compass, for de- 

 scribing arcs of circles having a radius too long to admit of their 

 being drawn by an ordinary compass, and a flexible steel bow, 

 for drawing a curved line through any number of given points 

 not less than three in number. 



It is best, if possible, to pin the drawing paper on which a 

 map is to be drawn on a drawing board of considerable size, or, 

 what is still better, on the well-planed top of a deal table, the 

 edges of which have been truly squared. The beam compass 

 can be used with ease on the flat top of a table, while the 

 management of this instrument on a board too small to include 

 the centres from which it is required to strike arcs of small 

 curvature is attended with difficulty, owing to the necessity of 

 taking the centres on a plane that is lower than the plane of the 

 board on which tho paper is pinned s, for example, when the 

 board is laid on a table in which we are obliged to fix the leg of 

 the beam compass round which the beam must revolve in striking 

 the arcs. 



The outline of a map consists of the delineation of the coast- 

 line, rivers, canals, railroads, etc. The coast-lino should be a 

 carefully-drawn line of uniform thickness throughout, more or 

 less broken by salient and retiring curves and angles, according 

 to the character of tho coast. The head-streams of rivers should 

 be finely traced, the main-stream being a line that gets thicker 

 and thicker as it approaches the coast-line. All angles should 

 be sedulously avoided in drawing a river's course. Canals and 

 railroads must be indicated by lines of equal thickness through- 

 out. All work of this kind should be done with etching pens 

 or good steel pens, as well as the names of towns, rivers, etc., 

 in smaller type or writing. The large names should bo outlined 

 with a pen and filled in with a brush, as the scraping of the pen 

 in colouring over a wide space makes the work look scratchy 

 when done. Swamps and woods may be drawn in with the pen, 

 and mountain ranges shaded with either pen or brush, the latter 

 being preferable for fine as well as coarser work. Degree lines 

 should be ruled with the finest of ruling pens, a larger and heavier 

 pen being used for the thick lines that form the outer border. 



Bo careful always to use Indian ink, as this will not run, like 

 ordinary writing ink, when the map is coloured. For colouring, 

 we should use colours derived from animal and vegetable sub- 

 stances rather than those obtained from mineral substances. 

 For instance, Prussian blue and indigo furnish far more even 

 tints than cobalt, and crimsen lake a smoother, less cloudy wash 

 than vermilion or red ochre. Mineral colours may, how. 

 used where variety is required in indicating boundary lines. 



We now pass on to describe Mercator's Projection. This 

 form of projection, which was invented by Gerard Mercator, a 

 mathematician and geographer who was born at Kupelmonde, 

 in the Netherlands, in 1512, is a projection of the earth's surface 

 on a flat sheet of paper, contrived in such a manner that the 

 relative proportions under every degree of latitude are pre- 

 served, although the parallels and meridians are represented by 



straight line, at right angle, to one 

 reader* a clearer idea uf what U 

 having an eitrwnely 



To fir* ocr 



eribing cylinder tonohinf the iptier* at the 

 sphere were then mbfeoted to a uniform 

 direction until it- elaitfo surface vac extended far 

 come into contact with the inside of th droaawcrtbiaff 

 the meridian* would bt extended into straight ji *nn*)iti*iaf 

 linen, and the parallel* into equal drele*. the whole beta* in- 

 scribed within tho cylinder. If the cylinder wen then oat open 

 down one of the meridian* and flattened oat, the interior womld 

 represent the form of projection known a* Mereator'* Pro)** 

 :... in which all the meridian* and paralM* IMUM the aapee* 

 of straight line* at right angle* to on* another. 



To draw the parallels and meridian* for a map of the world 

 on Mercator's Projection, finit draw a straight line, A B, a* in 

 Fig. 19, in a horizontal position, and through a point c in it, 

 taken a* near tho centre a* poaaible, draw the straight line 

 at right angle* to it Then enm* a *paoe for 6, 10, 16, or 

 20, on the equator, which U represented by the tin* A B, and 

 sot off 30, 18, 12, or 9 of these (pace* accordingly from the 

 point of intersection c of the two straight line*, along c A and 

 c B. In Fig. 19, we have assumed 15 a* the pace between the 

 meridians to bo laid down on the map, and from c twelve pace* 

 have been set off on either side along c A and c B, numbered 15. 

 30, etu., and terminating at the point* r and o, al*p marked 

 180 west and 180 cast. Through r and o, two * trait; ht lines 

 H K, L M must be drawn, cutting A B at right angle* and parallel 

 to D E. They will determine the limits of the map on the we*t 

 and cast, but it is sometimes thought necesaary to repeat the 

 last meridional division on one side of the map upon the other 

 in order to show the connection more clearly, but this i* not 

 absolutely necessary. Now in the sphere, a* the meridian* 

 approach the poles, the arcs of latitude included between any 

 pair of these diminish; but in Mercator's Projection, a* tho 

 meridians are represented by parallel straight line*, the ditano* 

 included between them remain* the same throughout ; the 

 parallels, therefore, must be represented by horizontal straight 

 lines parallel to the equator, but placed at distance* from it, 

 which increase in proportion, the more distant the parallel* are 

 from the equator instead of being at equal distances, a* when 

 they are represented by circles as in the sphere, arc* of circle* 

 as in the conical form of projection, and by right line* as in the 

 method adopted for drawing the maps of Africa and Sooth 

 America. 



The proper distance of every parallel of latitude from the 

 equator in Mercator's Projection has been calculated by a proo*M, 

 to understand which requires a knowledge of trigonometry, and 

 the results embodied in the table given below, in which the 

 distance of each parallel of latitude, the tropics and the arctic 

 and antarctic circles, has been shown in terms of minute* of the 

 equator. 



TABLE FOE THE CONSTRUCTION OF MAPS ox MEKCATOK'S 

 PROJECTION, SHOWING THE DISTANCE OF EVERY PABAI*- 

 LEL OF LATITUDE FROM THE EQUATOR ix TERMS OF 

 MINUTES OF THE EQUATOR, 



Mins. 



60-00 

 120-02 

 180-08 



LMn--i 



n*68 



360-66 

 481-Ofi 



4M 



i;o.; us 

 664-10 



wa 



7MI7- 



14 848-50 



15 ' 910-46 



16 I 972-74 



17 1035-30 



19 1161-50 



20 



21 



22 



23 



23} 



24 



25 



26 



27 



28 



29 



30 



31 



32 



33 



34 



35 



36 



37 



Mina. 



1125-14 



i:;:,.:-7" 

 Hi-;i 



u- !"; 

 1550-00 



u;i.; t- 

 i-x: ;._ 

 1751-16 

 1-10 U 



ntfii 



8171-48 



-.'.U-' 



B81MO 



4:; 

 41 



s 



17 



M 

 M 

 ftl 

 M 

 H 



54 



u 



M 



Mias. 



M68-M 



2544-94 

 MT70 

 MTM 



MS -aa 

 mg-94 



311555 



nos-Ti 



Sftfl-M 



MM 



:i-u :. i 

 WM 



I 



57 

 58 

 59 

 60 

 61 



n 



63 

 64 

 65 

 N 



07'' 



H 



69 



70 



71 



78 



73 



74 



1 1-J-. 



N - 



; ,. | : ; 



Ml H 

 4. ..-.. 



IBM M 



tan i. 



MI n 



NOfM 



S47402 



N-M 



M-- M 



nesia 



Ml N 



Ml *: 

 6745-74 





Xias. 



