tives came to an end."

[Footnote 31: Altdorfer's _Beautiful Virgin of Ratisbon_, about
1520, (B. 51, vol. 8, p. 78) made use of five colors in some
impressions (Lippmann describes one with seven colors) but these
were used primarily for decorative, not naturalistic purposes.]

[Footnote 32: Laurence Binyon, _A Catalogue of Japanese & Chinese
Woodcuts in the British Museum_, London, 1916, p. xx,
introduction.]

In making his Ricci prints Jackson sought a method of color printing
that would overcome the deficiencies of Jacob Christoph Le Blon's
three-color mezzotint process. Le Blon, a Frenchman born in Germany, had
begun experimenting with color printing as early as 1705. His idea was
to split the chromatic components of a picture into three basic hues--
blue, red, and yellow-- in gradations of intensity so that varying
amounts of color, each on a separate copper plate, could be printed in
superimposition to reconstitute the original picture. This was based
upon a simplification of Newton's seven primaries. Later, Le Blon added
a fourth, black plate. Incredibly, this is the principle of modern
commercial color printing, the only difference being that Le Blon did
not have a camera, color filters, and the halftone screen at his
disposal and had to make the separations by hand. Le Blon came to London
in 1719, produced an enormous number of color prints, published his
_Coloritto, or the Harmony of Colouring in Painting_ in a very small
edition about 1722 (it is undated), and shortly thereafter failed
disastrously. About 1733 he returned to Paris, where he attracted a few
followers. Most of his prints have disappeared, only about fifty being
known at present.

[Illustration:
Trial proof of the key block of center sheet of _The Crucifixion_,
after Tintoretto. National Gallery of Art (Rosenwald Collection).]

[Illustration:
TRIAL PROOF of the key block of _Christ on the Mount of Olives_,
after Bassano. National Gallery of Art (Rosenwald Collection).]

The idea of full-color printing, then, was in the air, although later,
in the _Enquiry_, Jackson took pains to state that he had not been
following in the footsteps of the Frenchman, who, he claimed, had made
serious mistakes.

The Curious may think that this Tentamine was taken from the
celebrated Mr. _le Blond_; I must here take the Liberty to explain
the Difference.... Numbers are convinced already, that the pr