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                       THE BOY MECHANIC
                            BOOK 2

  [Illustration: FOUR-PASSENGER COASTING BOBSLED See Page 24]

                             THE
                        BOY MECHANIC
                           BOOK 2

                 1000 THINGS FOR BOYS TO DO

                      HOW TO CONSTRUCT

  DEVICES FOR WINTER SPORTS, MOTION-PICTURE CAMERA, INDOOR
        GAMES, REED FURNITURE, ELECTRICAL NOVELTIES,
             BOATS, FISHING RODS, CAMPS AND CAMP
               APPLIANCES, KITES AND GLIDERS,
                     PUSHMOBILES, ROLLER
                       COASTER, FERRIS
                            WHEEL

                             AND

      HUNDREDS OF OTHER THINGS WHICH DELIGHT EVERY BOY

                   WITH 995 ILLUSTRATIONS

             COPYRIGHTED, 1915, BY H. H. WINDSOR

                           CHICAGO
                    POPULAR MECHANICS CO.
                         PUBLISHERS



       *       *       *       *       *

Transcriber's Note:

This etext differs from the original as follows. Two minor typographical
errors were found and corrected. In the chapters on making fly-fishing
rods (pages 59-71), several lists of materials or dimensions that were
printed as running text have been reformatted as lists for clarity. The
text is unchanged.

       *       *       *       *       *

[Illustration: After the First Station has been Selected, It is Marked by
a Pile of Stones, a Stake, or, If Precise Work is to be Done, a Tack in
the Top of a Stake. The Table is Then Set Up over This Station Point and
Leveled So That the Surface of the Paper will Be Truly Horizontal
(Inset: UNCLE JOHN'S FARM Scale 1/16" = 1' Jimmy Smith--Surveyor) ]

[Illustration: The Boy Surveyor]




Plane-Table Surveying By Harold G. McGee


    [In the training of a boy for a trade or profession there is
    none so profitable for outdoor work as that of a surveyor. This
    article sets forth how to accomplish surveying and the making of
    simple maps with the use of commonplace tools that any boy can
    make.--Editor.]

Surveying and map making have always been two of the most interesting
things a civil engineer has had to do. And, like George Washington, many
of the men we look up to today as successes in different lines worked as
surveyors in their younger days. Surveying takes one out of doors, and is
apt to lead him into the unknown and unexplored byways of the earth.

Though modern surveyors often use precise and expensive instruments,
creditable surveys can be made with simple and inexpensive apparatus. Of
such apparatus, two of the simplest are the plane table and the camera.
Since one must know the principles of plane-table surveying before he
can do camera surveying, this paper will describe the plane table alone,
leaving the camera for another chapter.

A plane table is simply a drawing board mounted on a tripod so that it can
be set up and worked upon in the field. One kind of plane table, which is
used in the army for reconnaissance, does not even have a tripod; it is
simply strapped to the arm of the man who is using it.

Plane-table maps vary greatly in scale and the area they represent.
Landscape artists' plans may show only single city lots, while some
topographic maps cover hundreds of square miles on a single sheet. For
maps of a small farm, a park, or a residence block in the city, a plane
table is almost ideal, since plane-table maps are made with rather simple
apparatus and do not require much actual measuring on the ground. Most
objects are located without ever going to them, or even sending a rod-man
to them.

[Illustration: Just a Few Weeks After George Washington's Sixteenth
Birthday, in 1748, Lord Fairfax, Owner of a Large Estate in Virginia, Took
Him into His Employ as a Surveyor]

Besides the plane table itself and a sheet of paper, only a small
carpenter's level, a tape to measure a few distances with, and some spikes
for markers, a hard lead pencil, a ruler, and a few needles are absolutely
necessary for this sort of a map.

[Illustration: Three Stations are Used for Setting the Plane Table in
Succession to Locate the Various Objects

TABLE AT STA. A - TABLE AT STA. B - TABLE AT STA. C ]

To start a plane-table map, a station must first be selected from which as
many as possible of the objects to be located on the finished map can be
seen. Ordinarily, the objects one would locate are corners of buildings,
fence corners, intersections of roads, corners of lots, banks of streams,
possibly trees, and section and quarter-section corners in the country.
A railroad, a lake, a mountain, or anything which forms a noticeable
landmark in any particular locality, ought to be on the map. In mapping
a territory which has never been surveyed before, the first surveyor may
name the hills and streams.

After the first station has been selected, it is marked by a pile of
stones, a stake, or, if precise work is to be done, a tack in the top of
a stake. The table is then set up over this station point and leveled so
that the surface of the paper will be truly horizontal. Generally, too,
the board is "oriented," that is, placed so that two of its edges point
north and south and two east and west. It is then clamped so that it will
not move while working on it.

To begin the map, a point on the table is chosen to represent the station
on the ground over which the table is set. This point is marked by
sticking a fine needle into the paper, vertically. A small triangle should
be drawn around the needle hole in the paper and labeled "Sta. A," so
that it will not be lost in the maze of points which will soon cover the
sheet. By sighting past this needle toward some object which is wanted
on the map, like the corner of a house, its direction can be marked by
setting another needle on the far side of the table, in line with the
first and the given object. Then, if a ruler or straightedge be placed
against these two needles and a fine line drawn connecting them, this line
will show the exact direction of the object from Sta. A. All the other
objects which are wanted on the finished map and can be seen from Sta. A
are located by direction in the same way.

The first points to have their direction thus marked ought to be the
next stations to be occupied. If all the objects to be located can be
seen from three stations, or even two of three stations, three stations
will be sufficient. The distance to one of them from Sta. A should be
carefully measured and laid off to scale along its direction line on the
map. Its place on the map should be marked exactly as the first station
was, substituting B for A. It is wise, after every few sights at other
objects, to take a sight along the line AB to make sure that the board
has not turned. A good map is impossible if the board twists.

To measure the distance between stations, a 50 or 100-ft. tape, or some
accurate substitute, is necessary. An ordinary piece of iron telegraph
wire, 105 ft. long, is a good substitute. A point, about 2-1/2 ft. from
one end, is marked with a little lump of solder. A chisel dent in this
solder will mark one end of the 100-ft. section. Then, with a borrowed
tape or a good rule, measure off and mark every 10 ft., just as the first
point was marked, until the entire 100 ft. have been laid off. The last
10 ft. should be divided into feet. In all this measuring and marking,
the wire must be stretched out taut and straight. The extra 2-1/2 ft. at
each end are used for making handles. By estimating the tenths of a foot,
measurements can be made with such a tape, or "chain," as an old-time
surveyor might call it, just as accurately as they can be laid off on the
map.

[Illustration: An Alidade, Consisting of Two Sights and a Straightedge,
Takes the Place of the Two Needles]

[Illustration]

Two men are required for measuring, or "chaining," a head and a rear
chainman. The rear chainman holds the 100-ft. end of the tape on the
station point, while the head chainman takes his end forward toward the
station to which they are measuring. When he has gone nearly the length
of the tape, the rear chainman calls "halt." The head chainman stops and
draws the tape up tight, while the rear chainman holds his division end on
the starting point. Then the head chainman sticks a spike into the ground
to mark the place where his division end comes, calls out "stuck," and
starts on toward the object point.

Large spikes make good marking pins, especially if they have little red
or white strips of cloth tied to them. Surveyors use 11 markers. One is
stuck into the ground at the starting point and is carried forward by the
rear chainman, who also picks up the markers at each 100-ft. point as soon
as the head chainman calls "stuck." In this way, the number of markers
which the rear chainman has in his hand is always the same as the number
of hundreds of feet which the last set marker is from the starting point.

In measuring between two points, care must be taken to draw the tape out
taut and straight, its two ends must be level with each other, and it must
be exactly in line with the two points between which the measurement