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tion of gum, glycerine, glue, etc., in making up the plaster, when the viscosity operates against crystallization. The treatment of plaster with alum and sulphuric acid, as snggested by him, and which is the most advantageous, diminishes somewhat its affinity for water, and thus causes it to set more slowly. The minimum of water can therefore be used in making it up, and, since it is perfectly anhydrous, it combines with a larger quantity of the water than the common gypsum, dries more rapidly, and becomes very hard. He also found that the caustic lime contained in plaster, resulting from the presence of carbonate in the gypsum, exercises a favorable influence upon its setting when mixed with water, since it combines with a portion of the water, producing an elevation of temperature and more rapid setting, and imparts a hardness doubtless due to its conversion into carbonate in the air. Common gypsum, containing 10 per cent. of lime, is said to give very excellent results, as it can be readily smoothed, and resists atmospheric influences better than plaster alone. Landrin has even prepared cements containing as high as 75 per cent. of lime.-13 C, November 1, 1874, 1369.

COLOR OF CHINESE BRONZES.

A chemical examination of some Chinese and Japanese bronzes of an unusually deep color, exhibited in Paris in 1869, has shown the existence of a much larger percentage of lead than occurs in the ordinary bronzes, proving that it is to this substance that the special composition and color of the bronze is due. Where zinc was present in considerable quantity, it seemed rather to counterbalance the effect of the lead. An alloy, composed of 5 parts of tin, 83 of copper, 10 of lead, and 2 of zinc, proved to be exactly like the Chinese bronze, and identical with it in fracture and polish. When heated in a muffle, it quickly assumed the peculiar dead-black appearance so greatly admired in Chinese bronzes.-21 A, Sept., 1874, 927.

ARTIFICIAL DECORATION AND HARDENING OF SANDSTONE.

The following process of artificially impregnating sandstone is said to be in successful operation at several German stone quarries. The stone operated upon is a porous sand

stone, which readily absorbs water to a certain depth, and the treatment consists in the successive introduction of a solution of an alkaline silicate and of alumina. The result is the production of an aluminous silicate within the pores of the stone, which gives to the surface a considerable power of resistance. The solutions employed are soluble glass and sulphate of alumina. After the process is completed, the stone may be polished like marble, which it greatly resembles. Heated to a high temperature, the exterior layer vitrifies, and may therefore be colored or decorated according to taste. The coloration may even be obtained by simply mixing the desired pigment with one of the solutions employed.

PRODUCTION OF PATINA, of differeNT COLORS, ON BRONZE.

The attention of Christophle and Bouilhet has been specially devoted for several years to the difference in the color of bronzes, and the method of reproducing them. Their investigations were controlled by the conclusion, reached after numerous experiments, that the patina of bronze can only be permanent when it results from natural chemical reactions, and is not developed by varnish or corroding agents. As a result, they exhibited brown, red, orange-yellow, and black colors. They state that they were obtained upon the surface by reactions which cause the production of suboxide of copper in two molecular modifications, and also of sulphide of copper. The objects allow of a coating of varnish. for protection, the chief condition of its successful application being the slowness with which it is done. The process, it is claimed, is practical and trustworthy, and it will reproduce the same three colors at any time. Addition of lead to the alloy is not necessary to produce the black patina, which under such circumstances has been found to be brittle and wanting in permanence.-14 C, CCXIII., 1874, 447.

PÂTE SUR PÂTE, A METHOD OF DECORATING PORCELAIN. The following is from an account of this method of decoration given by Professor De Luynes, of the Conservatoire des Arts et Métiers, Paris. A faint drawing is first made on the article, completely formed in unbaked porcelain. All the details are then represented by means of a colored

mass, diluted with water to the consistency of paste. The composition of the latter must be similar in nature to that of the porcelain, and its degree of contraction must be the same, so that the subsequent heating does not cause them to separate. The oxides employed as pigments must be so refractory as to resist the temperature of the porcelain oven, and not be converted in it into colorless silicates, or a dead coloring. The selection of pigments is therefore very limited. The colored páte is laid on by the artist with a brush, and he regulates the distribution by the drawing, and the manner of laying it on by the number and thickness of the coatings, according to the relation that the color of the mass and its thickness must have to each other in the finished article. The appearance of relief is produced partly by the brush, and partly by a variation in the number of coatings, and by the manner of laying them on, and may be still further heightened by the employment of an instrument with which a true relief is given. The article is subsequently subjected to all the processes of undecorated porcelain. While articles produced by this method, by the aid of some of the best artists, have been greatly admired, and although it may combine all the excellences necessary to the production of works of art, they must necessarily be very expensive, on account of the long and minute labor required of the artist, and the risk to which the article is subsequently subjected in the baking.—13 C, Nov. 1, 1874,

1368.

STARCHING LINEN.

The following is recommended by a German journal: Make a liquid paste with good fine wheat starch and cold water, and then stir in boiling water until a stiff paste is formed, and immediately add white wax, or stearin, say about one ounce of wax to a pound of starch (the exact proportions, however, in any case can only be determined by experience). If it is desirable that the linen should be very stiff, powdered gum-arabic may be added to the cold water with which the starch is mixed. The strained starch should be thoroughly rubbed into the articles after they have been well wrung out, after which they should be placed be tween dry cloths and passed through the mangle, and then

rubbed on an ironing-board in one direction with a soft rag, to distribute any lumps of starch. Collars, etc., should be ironed dry, with a hot iron and considerable pressure. The sticking of the iron may be prevented by drawing it, while hot, over wax, and wiping it with a rag dipped in salt.-15 C, XXIV., 1874, 380.

PASTE FOR PHOTOGRAPHS.

Paste prepared as follows is highly recommended by Tunny for photographs: Mix thoroughly 630 grains of the finest Bermuda arrowroot with 375 grains of cold water, in a capsule, with a spoon or brush, then add 10 ounces more water and 60 grains of gelatin in fine threads. Boil, with stirring, for five minutes, or until the liquid becomes clear, and when cold stir in well 375 grains of alcohol and 5 to 6 drops of pure carbolic acid. Keep in well-closed vessels, and before use work up a portion carefully with a brush in a dish. It is said to keep for a considerable time.-15 C, XXIII., 1874, 357.

MUCYLINE, A COMPOSITION FOR OILING WOOL.

The so-called mucyline, for oiling wool, consists of sebacic acid, 19.8 lbs. ; potash soap, 19.8 lbs. ; glycerine, 11 lbs.; sulphate of zinc, 154 grains; and water, 55 lbs. The scbacic acid is carefully mixed with the glycerine, or instead of it with a vegetable or animal mucilage, and the soap is then added. The mixture is then diluted with 104 quarts of water at 176°, in which the sulphate of zinc has been dissolved, and the rest of the water is then added very gradually, with continual kneading of the mass. The very tough, homogeneous paste thus formed can be kept for two weeks, or even longer, and the mucyline, which is a liquid of a density 1.025, may be prepared from it, by adding to 35.2 lbs. of it 39.6 lbs. of water, either cold or warmed to 68°-77°, according to the season, and filtering the liquid or allowing it to settle.—32 C, April 10, 1875, 174.

WATER-PROOFING COMPOSITION FOR BOOTS.

A mixture made as follows is said to render leather water-proof and pliable, as well as far more durable, and at the same time does not prevent its taking ordinary blacking:

Take three parts of green cart-grease, one of lard, and half a part of common comfrey. Chop the latter quite fine, and boil to a thick paste with water, and free it from fibres by straining. If the leather is very hard, more comfrey should be taken. Before the application of the mixture, the boots should be rendered pliable by moistening them with warm water, and after they are thoroughly coated with it, especially the soles and seams, they should be allowed to dry slowly in the sun or near the stove. The operation should be repeated every two weeks, at least upon the soles and seams. -26 C, IV., 1875, 37.

RAPID BLEACHING OF LINEN,

According to the experience of some, time may be saved by bleaching linen by the following process: Rub the linen as it comes from the loom, in a dry condition (best on a table), with a brush, with a lather of soap made by boiling 1 lbs. of soap for a piece of coarse linen, or 1 lb. for a piece of fine, and allowing it to cool; then cover the linen in a tub with a cloth. Prepare a lye, for a piece of linen, by boiling half a bushel of good sifted beech-wood ashes in rain or spring water, and filtering it through a lye-basket; bring it to boiling in a clean kettle, and pour it upon the linen. Cover the vessel well, so that the warmth and moisture may be retained as long as possible, and allow it to stand overnight. Spread the linen on the grass in the morning, see that no spots become dry during the day, and cover at night again with the boiling lye. Turn the linen out the second day, and expose as before, without allowing it to become dry, and steep it overnight in weak hot soap-suds in a well-covered vessel. Wash out the dissolved dirt in the morning, and expose again, without allow ing it to dry before evening, and then treat in the usual way until it is as white as may be desired; six to eight days often being sufficient. If necessary, however, the soaping and steeping may be repeated as before, when only two days additional bleaching will be required.-9 C, July, 1874, 102.

RAPID BLEACHING PROCESS.

The following processes are given by the Muster-Zeitung: The washed material is steeped from six to twelve hours, ac