impregnate them with mastic varnish for the purpose of excluding air
and moisture, as Mr. Laurie proposes, in order to preserve the colors
of oil paintings, it is perhaps well to bear in mind the principle
here alluded to as a possible solution of the difficulty.

I have dwelt rather long on this important question of the action of
light on dyed colors, but I have done so because I thought it would
most interest you. With the remaining portions of my subject I must be
more brief.

(_To be continued._)

* * * * *


To introduce free fat acids from an oil, it must be decomposed. This
may be done by the use of lead oxide and water or by analogous
processes. To clarify an oil, expose to the sun in leaden trays. Often
washing with water will answer the purpose.

* * * * *




COMPOSITION OF WHEAT GRAIN AND ITS PRODUCTS IN THE MILL.


Probably the most striking difference in the average mineral
composition of the grain of wheat is the very much lower proportion of