f being used with water as a diluent or with
oil,--thus being a kind of union of the earlier temperas and the oil
medium. This borax-glass vehicle was certainly a discovery, or
rediscovery, as he was inclined to think it, of our highly valued friend,
P. Rainier. We say re-discovery, remembering his playful assumption of a
motto, "Veterem revocavit artem." He was probably led to this use of a
glass composed of borax, by the vitrification of the pigments; and we
still suspect that, in some of the old Italian recipes, glass, with borax
as an ingredient, will be found. "_A peculiar kind of Venetian glass_,"
says Mr Eastlake, "used, when pulverised, as a dryer, contained a
considerable portion of lead; and if it acted chemically, may have derived
its siccative quality from that ingredient." The question here naturally
suggests itself, Why was a peculiar glass used for this purpose, when it
was perfectly well known that lead of itself would have been sufficient?
Again, in page 358, from the Mayerne MS., as quoting the authority of
Mytens; "This oil (mancop) does not dry of itself easily, but it is
usually ground with Venetian glass, and thus to the sun in a glass bottle.
This should be shaken every four days for three or four weeks: it should
then be carefully decanted for use, leaving the sediment with the glass."
It is a question if the glass was here solely used to facilitate the
sediment.

Vitrification would not depend upon the introduction of glass
only,--calcined bones, which, it is now known, were much used in vehicles,
will produce the same result. In a note, page 345, Mr Eastlake says that
he requested Mr Marris Dimsdale to analyse a fragment of a picture by
Cariani of Bergamo, (a contemporary and scholar, or imitator of
Giorgione;)--the result being, that "one portion ran fairly into a
vitrified state. Hypothetically," adds Mr Dimsdale, "I should say it had
burned bones in it." And again, "Every colour mixed with phosphate of
lime, (calcined bones,) vitrifies when exposed to strong heat. As Venetian
pigments vitrify, might not phosphate of lime have been used as a dryer?"

We cannot but suspect any medium under which the pigments will not
vitrify. The publication of Mr Eastlake's most important and valuable
volume, rather strengthens our reliance upon the various communications
made to us by Mr Rainier. For instance, many years ago, we used, at his
recommendation, sandarach, dissolved in spike oil, and then mixed w