But, turning from the purely pictorial side, let us consider the material side of stamps and the various methods employed in producing them.  The design having been selected, it becomes necessary to reproduce it in some form suitable for making stamps in large quantities.  In a general way we may divide stamp printing into two classes:  printing from metal plates and printing from stone, or lithography.  The first class contains two grand sub-divisions.  In the first of these sub-divisions the lines to be reproduced are sunken below the surface of the plate.  This is known as taille douce or line engraving.  It is also called copper plate and steel engraving.  The copper plates for our visiting cards are familiar examples of this style of work and our national paper currency presents very beautiful and elaborate results of the process.

The second sub-division is known as typography or surface printing.  As its name indicates, the lines to be reproduced are at the surface of the plate, the other parts being cut away.  A newspaper is an example of typographical printing, the term being applied to designs made up from type, as well as to specially prepared plates.

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 stamps.