DOI Seite / Zitierlink:
https://doi.org/10.11588/diglit.20658#0368
354
PROJECTION.
extreme parallels onlv, as above, but on every intermediate one diminished, as was already
mentioned, and through all these corresponding points in the several parallels draw the meri-
dians, which will be not right lines, but curves. This method answers very well for a large tract,
as Europe, where the parallels and meridians need be drawn only to every 10 or 5 degrees; and
all the parts of the map are very nearly in their due situations excepting the outside, where they
are somewhat distorted by the oblique intersection of the meridians and parallels.
Again, a third method is to draw a line of a convenient length for a meridian; divide it into
nine equal parts, and through the points of division describe as many circles for the parallels of
latitude from the centre, which here represents the pole. Divide the equator into equal parts of
the same size as those of the meridian ; divide also the parallels into the same number of
equal parts, but each part smaller in proportion to the number of miles in a degree, according
to the former rule. Then through all the corresponding points of division draw curve lines,
which will represent the meridians. When the degrees of latitude and longitude are marked,
and the proper scales laid down, the map is ready to receive the names and places. This is
called the globular projection, and answers extremely well for large maps, all the parts of the
earth being represented nearly in their due magnitude, excepting still that they are a little out
of their proper shape and position, towards the outside of the map.
When a map is to be made of a small district, as a country, &c. the meridians will, as far as
our senses can discover, be parallel one to another, and the whole will differ very little from a
plane, and may be the more easily made as such than by the foregoing rule, for it will be suffi-
cient to measure the distance of places in miles, and to lay them down on a plane rectangular
map. But the collecting of materials for this operation belongs properly to surveying, to be
noticed hereafter.
The use of maps is obvious from their construction. The degrees and minutes of the meridians
and parallels point out the latitudes and longitudes of places, and the scale of miles serves to
measure their distances; and the situation of places with regard to each other, as well as to the
cardinal points, appears by inspection : for the top of the map is always turned to the north,
the bottom to the south, the right hand points to the east, and the left hand to the west;
unless the mariner's compass, usually annexed, should indicate the contrary.
chap, ir;
OF SURVEYING.
SURVEYING is the art of measuring land, and comprises the three following parts :—-
1. Taking the dimensions of any tract or piece of ground.—2. The delineating or laying down
the same in a map or draught.—And 3. The finding of the superficial contents, or area of the
same. The dividing and laying, out of lands are also branches of surveying. Of these three
heads the first is what is properly called surveying; the second is called plotting, protracting or
mapping; and the third is casting up, or computing the contents.
The first again consists of two parts—the making of observations for the angles, and the taking
of lineal measures for the distances. The former of these operations is performed by some one
of
PROJECTION.
extreme parallels onlv, as above, but on every intermediate one diminished, as was already
mentioned, and through all these corresponding points in the several parallels draw the meri-
dians, which will be not right lines, but curves. This method answers very well for a large tract,
as Europe, where the parallels and meridians need be drawn only to every 10 or 5 degrees; and
all the parts of the map are very nearly in their due situations excepting the outside, where they
are somewhat distorted by the oblique intersection of the meridians and parallels.
Again, a third method is to draw a line of a convenient length for a meridian; divide it into
nine equal parts, and through the points of division describe as many circles for the parallels of
latitude from the centre, which here represents the pole. Divide the equator into equal parts of
the same size as those of the meridian ; divide also the parallels into the same number of
equal parts, but each part smaller in proportion to the number of miles in a degree, according
to the former rule. Then through all the corresponding points of division draw curve lines,
which will represent the meridians. When the degrees of latitude and longitude are marked,
and the proper scales laid down, the map is ready to receive the names and places. This is
called the globular projection, and answers extremely well for large maps, all the parts of the
earth being represented nearly in their due magnitude, excepting still that they are a little out
of their proper shape and position, towards the outside of the map.
When a map is to be made of a small district, as a country, &c. the meridians will, as far as
our senses can discover, be parallel one to another, and the whole will differ very little from a
plane, and may be the more easily made as such than by the foregoing rule, for it will be suffi-
cient to measure the distance of places in miles, and to lay them down on a plane rectangular
map. But the collecting of materials for this operation belongs properly to surveying, to be
noticed hereafter.
The use of maps is obvious from their construction. The degrees and minutes of the meridians
and parallels point out the latitudes and longitudes of places, and the scale of miles serves to
measure their distances; and the situation of places with regard to each other, as well as to the
cardinal points, appears by inspection : for the top of the map is always turned to the north,
the bottom to the south, the right hand points to the east, and the left hand to the west;
unless the mariner's compass, usually annexed, should indicate the contrary.
chap, ir;
OF SURVEYING.
SURVEYING is the art of measuring land, and comprises the three following parts :—-
1. Taking the dimensions of any tract or piece of ground.—2. The delineating or laying down
the same in a map or draught.—And 3. The finding of the superficial contents, or area of the
same. The dividing and laying, out of lands are also branches of surveying. Of these three
heads the first is what is properly called surveying; the second is called plotting, protracting or
mapping; and the third is casting up, or computing the contents.
The first again consists of two parts—the making of observations for the angles, and the taking
of lineal measures for the distances. The former of these operations is performed by some one
of