I need not suggest to you how wide a field for thought and exploration
this subject of engraving opens to us, leading as it does directly into
the world of books, pictures and art. But at present we must confine
ourselves to the subject as applied to postage stamps, save for a brief
consideration of its origin and history.

The art of engraving owes its origin to the Florentine goldsmiths of the
fifteenth century. They were accustomed to ornament their work with
incised lines which were filled with black enamel. A design thus filled
with enamel was called a _niello_, a derivative of the word _nigellum_
(the most black). The brass and nickel signs with black letters, which
we find at the doors of business houses, are modern forms of _nielli_.
While making a _niello_, the artist naturally wished to see how the work
was progressing and if any alterations were required. It was not
desirable to put the enamel in the design because it was difficult to
remove. To avoid this an impression of the work was taken in clay, from
which a sulphur cast was made. The lines of the cast were filled with
lamp black. Thus a copy of the work was obtained which reproduced its
coloring and showed the condition of the engraving. A more simple
process was discovered later. This consisted in filling the lines of the
engraving with a thick ink and pressing a sheet of damp paper against
them. Sufficient pressure was used to force the paper into the lines and
take up the ink on its surface. This was the beginning of line engraving
and plate printing. The process was at first employed for the
preservation and duplicating of designs for goldsmith's engraving and
afterwards for the sake of the work itself. It was not until the next
century that the process assumed a leading place in the world of art. If
it were not going too far away from our subject we might study the early
engravers and their work with much profit and entertainment. But it is
our purpose to consider the subject only so far as it applies to postage