Weekly national intelligencer. [volume] (Washington [D.C.]) 1841-1869, 1848-12-23
THE ELECTRoTYPE DEPARTMENT OF THE
COAST SURVEY.


The following facts were gathered togerner b,
the writer while examining that department Of tn,
Coast Survey where are drawn, engraved, and print
ed the beautiful charts and maps OF that scientific
bureau
The eectroype process invented almost simultaneous
" in Great Britain and Russia in the year 1888 the palm
of precedence however, is generally awarded we believe,
German named JAcoBI, while in the employ OF the Empe
ror Of Russia and the idea said to have been suggested
his mind by the accidental dropping OF copper coin into
solution of copper and zinc when under the influence OF
pavaic battery The coin greatly enlarged, and wher
the two masses finally separated by way Of experiment
was discovered that counterpart impression of the coir
made upon the outside coating The process alluded
was first applied the copying Of small objects in relief such
as coins and medals The coin medal to be copied Cor
cast from it in mea soldered to wire forming the
gave pole Of gsvanic battery piece of copper of SINH
lar dimensions then attached to the positive pole and
placed opposite the Of the medal, and at moderate
distance from it. in solution Of suphae Of copper blue
yiol ahe battery being set in opeaton the copper Of the
plate the positive pole dissolved and transferred to the
negative pole where deposited the surface of the
medal conforming with the utmost mnuteness to every cavi
elevation. Separating the elecoype depcste from the
mould relief produced corresponding ntaglo,
and an intaglio 10 relief.
was soon seen this electroype process might be APP
piled with great advantage to the copying Of engavng
GLIDING those of maps and charts but the difficulty
the adhesion Of the eecoype plate the surface
the original thus destroying the prints Of the engraver
copper plate yields very limited number of impressions
before the Of the surface destroys the sharpness of the
engraved lines, defects in the plate render the whole
face blued Engraving steel is very expensive pro-
owing the slow progress made by thu grave the
L..I A.
rapidly into thin size, to which Init is below
that which necessary for large maps. II is of
great advantage retain the soft and easily worked
ply the number Of copies from the engraved plate
definitely.
This is effected through the electrotype process plate
relief is obtained by depoe the surface of he engrav
ed copper plate, and from this relief any nunbe Of copies
may be made which perfect fac SMILES of the original
engraved plate So perfect that scratches into the bur
nisher plate repeated the other and the very
finest engraved lines sharply copied There is differ
between impressions taken from the plate from
difference in wpng of the ink and other accidental variations
in printing, than between impression taken from original
plate and its eecotype copy under like circumstances of
printing.
This process has been applied the maps and charts of the
Coast Survey since 1896 One of the engravers the Office
Mr. Senar Sleber has under the immediate direction of the
Superintendent prof BAcHE completely mastered the pro-
and applied to all the maps and charts engav-
ed, that the originals preserved in most without
injury from printing The process may be regulated
produce metal of different degrees of oughness and hardness
and make the deposite slowly rapidly the fine
parts of the plates be copied the plates merely
to be increased in thickness to give the requisite Stiffness
Blank plates for engraving upon also made by this
At first the adhesion of the plates prevented by slight
slverng of the surface thin not TO interfere with the
perfection of the copy, and yet preventing the close contact
of the copper surface snecessay their firm adhesion Now,
slight oxidation Of the surface is effected by process first
used in the copy Of the ordnance maps Of Great Britain,
which the purpose This elecoypng, thus
applied, Is ond important branch of the minute
circumstances which influence the results requiring study
and intelligent experience to effective control Of the
process In has plate been lost in the survey
process by adhesion.
With regard TO the size Of the plates executed in the Office
of the Coast Survey, it may be stated that they vary from
eighteen to thirty eight inches in length, and fourteen hr
tyfour in width, though occasional plate Of smaller d.
mansions is executed The time employed in producing the
original engrayngs varies from six twenty months and
nine ten engrayers employed in the Coast Survey at
the present time To describe the maps and charts whihe
drawn, engraved and printed by the Coast Survey would be
superauous task, they repued 10 be the beau
u and the which have yet been executed
in this any other country.