W. lon. and 18 N. lat. To put it on the Wall. About two thirds beyond the 7th division on the W: Wall, you have 77 deg. then cast your eye on the meridian of London, and nearly as high as 20 will be the lat. 18 degrees N. and this is the spot on the Wall where this island may be fixed; and in the same way may any other place or island be transferred from a Map, &c. to the Wall occupying a space according to its dimensions. In like manner may the parallels of lon. and lat. be drawn for any places on paper, and those places inserted, if the longitudes and latitudes are known.

Here follow two Examples, one North, and the other South Latitude.

Exam. I.-Draw the parallels of lon. and lat. that will include Constantinople, Petersburgh, Suez, and Bagdad. (You will find these places in the table, with the words joined to express the longitude and latitude.) When you intend to lay down a country or places, you have nothing to do but consider the greatest N. and S. lat. and E. and W. lon. or in other words, what parallels of lon. and lat. the country or places you wish to insert lie between. In the foregoing Example, Constantinople has the least E. lon. (29 deg.) and Bagdad has the greatest lon. (44 deg. E.) therefore, the first having less than 30 E. I must begin with the meridian of 20 deg. and Bagdad being more than 40 E. I must extend it to 50 deg. E. or the fifth meridian beyond London.-Suez is 30 deg. N. and Petersburgh 60, so that we find 30, and 60, the two extremes of lat-all other places that you find lying between those parallels of lon. and lat. you' may insert. The other Example is in S. lat. which

you cannot fail to understand, if you have read this last with attention.-See them all laid down in the following plate.

Observations on General Maps, and how to understand them.

A general Map is such as treats of many countries, as a Map of Europe, Asia, &c.

When you open a Map that you are unacquainted with, look along the top, and see if you can find the meridian of London in it, (which is al✦ ways marked with an 0,) and if it is not there, observe if the numbers increase towards the right hand, for if they do, the whole of the Map is E. lon. as a Map of Asia, or China. On the contrary if the numbers are higher towards the left hand, it is W. lon. but if they increase both right and left, it is evident that the meridian of London will be found running somewhere thro' the Map, and shews it to possess both E. and W. lon. as the Map of Europe, England, &c.

To know at the first glance whether a Map is N. or
S. latitude, or both.

Look at the side and observe if the numbers increase from the bottom towards the top of the Map, and if they do it is N. lat.-if the numbers are larger towards the bottom it is S. lat.-but if they increase upwards and downwards, it denotes the Map to have both N. and S. lat. and the Equator (marked 0) must run somewhere thro' the Map.This is the case when North and South America are delienated on the same Map; for S. America will extend to about 55 degrees S. lat. and North America to nearly 80 degrees N. lat.

Examples for drawing your parallels of lon. and lat. see page 151.

Exam. I. Constantinople, 29 E.-41 N.-Petersburgh, 30 E.60 N. Suez, 33 E.-30 N.-Bagdad, 44 E.-33 N.

Ex. II. St. Helena, 6 W.-16 S.-C. of Good Hope, 18 E.--34 S.

St. Helena being W. lon. and the Cape East, we must of course have the meridian of London, somewhere in the interior part of the Map, which you will here perceive distinguished by a nought; so that you have 6 deg. W. and 20 E. and from 10 deg. S. to 40, which is sufficient to include these places, and all others lying between those parallels.

To face P. 152.

The Student must be sensible by this time, how essential it is to get by heart the lon. and lat. of places, for that being done, he can in an instant draw his parallels and insert them, either on the plane of Mercator, (i. e. straight lines,) or on a Stereographic projection, (i. e. like a Hemisphere.)

I do not use minutes in the lon. and lat. as there is no occasion, unless when accurate calculations are wanted to be made; and then it may be done by taking two words for the lon. and two for the lat. and then the first word for each will stand for the degrees, and the second word will denote the minutes in making out the lon. and lat. of places, if the minutes exceed 30, take a whole deg. for them, but if they are under 30, take the preceding deg. so that you will always be within a few minutes.

you,

When you have fixed your countries and places by the eye (of the mind) on the Walls of your Room, you will only have to recollect two short words for the deg. of lon. and lat. of any place. Whatever places occupy your upper Room must be N. lat. and those which are found in your lower Room must be S. lat. as I have already told that your Floor is to represent your Equator. All places that are found to the right of the meridian of London, (whether in N. or S. lat.) will have E. lon. and all places on the left hand of the meridian of London will possess W. lon. so that the words, (at) and (with) (is) and (was) may be dispensed with, when once you know what Wall and Room any place is in. Also, those who are already acquainted with the Science will have but two words for recollecting the number of deg. for both lon. and lat.-Example, instead of saying, at Archangel in Russia, is a fat mule, I would only

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