JUICES OF PLANTS. Papers stained with the juices of various plants are altered in colour by exposure to sunshine. Sir John Herschel, some years ago, communicated to the Royal Society the results of many interesting experiments made by him on the juices of plants. His method of proceeding was, to crush the petals of the flower to a pulp in a marble mortar, either alone, or with the addi tion of alcohol, and to express the juice by squeezing the pulp in a linen cloth ; it was then spread upon paper with a flat brush, and allowed to dry spontaneously in the dark. The tint communicated to the paper is not always that of the petal of the flower. The most sensitive colour met with was that of the Corchorits Japonica, the yellow tint of which is speedily bleached by sunshine. Paper stained with the blue tincture of the double purple groundsel is completely bleached by light. The juice of the Senecio nplendidue imparts a rich and deep velvety purple tint to paper, which is very insensitive to light.
We may add that the juice of the Ithus etriata, of South America, and of the Miss venenata, or poison tree, of North America, both communicate indelible black stains to paper. The latter has been used for marking linen.
Among the juices of plants are many important dyes, such as indigo, madder, saffron, &c., &c., many of which are bleached more or less by light. In the case of indigo, however, the expressed juice from the leaf of the indigo plant is originally colourless, but is darkened to a deep purple tint by exposure to air and light. This dye is very permanent.
KA°Lmr. Porcelain clay, used for decolorizing discolored nitrate baths, and other solutions. The best way of using it is to add' a little to the solution, shake well up together several times, and then let it stand to settle ; afterwards decant the clear liquid.
Kaolin is a fine pure white clay prepared by levigation from mouldering granite, and used for making vessels of porcelain. It contains nearly equal parts of alumina, or pure clay, and silica, together with about one per cent. of lime and oxide of iron. It is found in veins in primitive mountain districts, chiefly in China and Japan, Saxony, the neighbourhoods of Limoges and Bayonne in France, and M England in the counties of Devon and Cornwall. We have also found it in Jersey.