Evening star. [volume] (Washington, D.C.) 1854-1972, 1891-03-14
CHARTS OF THE COAST
How They Are Engraved and Turned
Out by the Coast Survey.
ACCURACY A NECESSITY.
Transferring Maps to Copper Plates-Print-
ing the Charts and Preparing Them With
Final Corrections for Publication-Agents
Employed by Uncle Sam to Distribute Them.
THERE Is A GREAT DEAL THAT IS OF


estuaries that go to make up the irregularities
of the country's shore line, as a STAR reporter
discovered in recent visit to the coast survey
bureau.
To begin with, Of course, elaborate surveys
must be made and maps produced, on which
not only the features Of the land are repre-
| sented, but also the depths Of the coastal
waters, by soundings recorded in numbers.
When these drawings are finished they are
| sent into the coast survey Office and are placed
in the hands of highly skilled workmen, whose
task it is to engrave them on copper
plates. Usually several hands are sue
cessively employed upon a single plate
before it is completed, because the task
is long one and so difficult that each
expert usually makes one particular
kind of execution his speciality. has not the
patience to do sand, which is shown by dots
put in so thickly with the steel point under a
magnifying glass that 10, 900 Of them are con-
much as one man can accomplish in day-and
prefers to make lettering. while B finds 1t more
to his taste to put figures for soundings In their
proper places than to show hills by fine lines
that. well done, will make a mountain stand
right up from the fiat paper seemingly and
even exhibit the shape of the elevation with
accuracy. 1t is all matter Of copying, but it
takes a great deal of study and practice to per-
form it correctly and as it should be.
DRAWING AND TRANSFERRING IN SECTIONS.
The map is transferred from tho original
drawing piece by piece, taking section of not
more than few inches square at time. until
the whole is complete. A little sheet of very
thin transparent fish glue is laid down over the
part Of the drawing to be copied and fastened
securely. Then the engraver, seeing the lines
of the drawing clearly through the fish glue.
traces them upon the fish glue sheet with a fine
steel point that cuts slightly into the substance.
After oil the lines beneath have been traced in
removed from the drawing. When it is held
up to the light the small piece of map is seen
to be accurately copied upon the fish glue.
Thereupon the operator rubs the side of the
film on which the tracing has been made with
pencil dust, which catches in the little scratches
made by the steel point, SO that it remains
there after the surface Of the film has been
gently rubbed of.
TRANSFERRED TO THE COPPER PLATE.
Next, the film is laid in its proper place upon
the smooth plate Of copper, with the traced
side down, and is held firmly in position while
the back of the film is rubbed with blunt in
strument. When this has been done the film is
removed and there remains upon the copper
plate perfect reproduction in pencil lines Of
the original section of map. 1t Is only neces-
sary for the workman to go over these lines
with his gravers that cut into the metal, in or
der to complete that part of his task after
| which he goes ahead with another section in
like manner. until the map has been transferred
entire to the copper. Such lettering has to
be put on the map, in the shape of title. notes
Of information, names Of places, and so on, is
not traced. bot is drawn directly on the copper
with craving tools specially made for the pur-
pose. after careful measurements have been
made to determine the exact spaces the words
are to occupy. The plates employed are of the
very finest selected copper, hammered so as to
make them hard.
HOW THE PLATE IS PRINTED.
Now, the plate is ready to print the charts
from and it is taken into the printing room for
that purpose. First it is gone all over with
big roller full Of ink after which all the ink is
rubbed off it. first with sponges and then with
the bare hands, until it is perfectly clean. the
ink only remaining in the lines of the engrav-
ing. Even the rubbing of the plate in this way
is quite art. for if it is not rubbed Just right
the ink will be rubbed out of the lines and an
imperfect print will be produced. After the
| rubbing has been completed and the plate has
been made to shine as brightly possible it is
put into a powerful press that is worked by
| hand with sheet Of paper that has been pre-
| viously moistened, and presently the latter
comes out with the perfect map printed upon
| it, while, owing to the great pressure exerted,
| not particle of ink remains on the plate. Be-
fore the nextcopy can be struck off the plate has
| to be linked again, and SO on with every print.
| The charts thus produced are dried for twenty
| four hours in hot room. and from this process
| they come out rather rough, so that to make
them smooth again they are placed between
sheets of leather and subjected to a pressure Of
| $50 tons.
| Row CORRECTIONS ARE MADE.
| Then they are ready to 60 out Of the Office,
unless, as is very likely to be the case, there
are corrections to be made. Buoys are con-
stantly being changed, fresh wrecks are oc-
curing to endanger navigation and all sorts of
| other things are happening that must be re-
corded up to the very date that the chart is
published. For this purpose the light house
| board is continually in communication with
the chief photographer in the coast survey Of
! fee, communicating the very newest informa-
ton respecting buoys placed or removed, alter
ations in light house SERVICE, &c. Besides,
| there may be other emendations of moment
and all must be made ere chart can be finally
approved. A special department is devoted to
this work and the experts there give their q +
tention to erasing from each chart what
should be erased and putting in whatever is
needed. If the situation OF buoy has been
changed they scratch it out from the old spot
and put it into the new one with little ink
stamp. Where red danger buoys have to be
introduced they put them in with red ink, and
| one Young woman devotes all her time to
painting with red paint the red streass Of light
| thrown by certain light houses which show that
/ color To mariners on the siueb WHere tnere Is
| danger. Finally each chart issued is stamped
with the words, "Aids to navigation corrected
| to date for information received 20 March Il, -
or whatever the day may be. ALI such correc-
| lions as these are called temporary correc-
TONS and they are not entered upon the cop
per plate by changing it.
ALTERATIONS IN THE PLATE.
From time to time permanent corrections
come in, from resurveys otherwise, and
these necessitate alterations in the copper
plate. Ordinarily they are made by simply
hammering fiat the metal surface and
re-engraving ON the same spot whatever it is
desired TO put in. But sometimes it is neces-
sary to erase something by cutting away the
copper surface. which is made level again by
turning it over and beating it on an anvil from
the back. This latter 10 the way in which en-
gravers o. visiting cards wipe out old addresses
in order to put in new ones. It is the simplest
and easiest thing in the world to do, but they
would have their customers believe that it il
very difficult and they charge accordingly.
TO PREVENT PHOTOGRAPHS FROM SHRINKING.
There is q special apparatus in use at the
coast survey Office for preventing photographs
OF maps from shrinking unevenly, 90 as to of.
feet their accuracy Any photograph is ALWAYS
smaller than the negative, because the paper on
which it is printed, having been moistened
shrinks Unfortunately, in shrinking it does
not preserve its proportions, the shrinkage
across the grain being sonnet thing like twice a
great as with the grain. Next time YOU have 4
photograph taken get the photographer to make
one copy with the grain Of the paper turned