we are indebted for it in its present improved state to the ingenuity and researches of Deville, whose method is a modification of Wöhler's. He received from the present Emperor Napoleon the funds necessary for making his experiments on a large scale, and in a satisfactory manner, and he first published an account of them in 1854. 339 found to be quite pure, it is heated with nails or ironturnings, in an earthen or cast-iron vessel, which, when the permanent gases have passed off, is closed; after which, the heat being continued, a slight pressure results that causes the chloride of aluminium to melt and come in contact with the iron. This changes the volatile perchloride of that metal into the protochloride, which is comparatively fixed, and the chloride of aluminium, completely purified, crystallises in the vessel itself in large transparent and colourless prisms, and a distillation in hydrogen finishes the process. To Obtain the Sodium.-Its preparation is founded on the reaction of an alkaline carbonate on carbon; and carbonate of soda, wood charcoal, and carbonate of lime are required in the following proportions :— Carbonate of soda · 717 175 108 1000 It occurred to him that, on account of its smaller equivalent, and the commercial value of its salts, sodium would be better for the purpose of obtaining aluminium than potassium, which had been employed by Wöhler. Other advantages, besides, were found to follow from its adoption. The manufacture of sodium is easier, and even safer, than that of potassium; and when the process goes on well, those carbon compounds which are so annoying with potassium, do not make their appearance, nor is its reduction accompanied by the explosive substancesprobably compounds of hydrogen-which are so dangerous in the reduction of potassium. Moreover, the use of potassium in obtaining aluminium is not very safe, -it inflames so easily, and often produces such violent explosions; while sodium can be employed without fear, The carbonate of soda should be obtained from crystals since it may be raised in the atmosphere to a higher dried and pulverised fine; the carbon and chalk should temperature than its point of fusion. Indeed, we have also be reduced to powder, and the whole, as soon as reason to believe that it is inflammable only in a state of possible after having been mixed, should be made into a vapour, though still at a temperature below its boiling-paste with very dry oil, and then calcined at a red heat point; and if it is kept very carefully from water, there in an iron mercury bottle, that it may occupy a small will be little likelihood of its taking fire. space, and thus a larger quantity of potassium be obtained To get pure aluminium by Deville's method, we requirejected to a high heat in an iron mercury bottle, which is by the subsequent process. The calcined mass is subpure alumina, pure chloride of aluminium, and metallic not so rapidly destroyed as might be expected, and ought sodium; for any impurities present in these will be conto last for three or four operations. It is kept comparacentrated in the aluminium, and affect its properties very tively cool by the resulting oxide of carbon, and by the much, nor, if once combined with it, can they ever be sodium assuming an aëriform state, and the heat required entirely removed. We shall first, therefore, describe is not near so great as might be supposed. An iron tube leads from the bottle, which is inside the furnace, to a receiver, which is outside, and has an aperture for the escape of the gases. The carbonic oxide formed from the chalk assists in carrying the vapour of sodium rapidly into the receiver, and thus prevents it from decomposing any of the gas by which it is necessarily surrounded,an effect that would be facilitated by its finely divided state as vapour. The receiver, also, is thus kept hot enough to unite the metallic globules without a wasteful after process. One-seventh of the weight of the mixture which has been used, or one-fourth of the weight of the carbonate of soda, should be obtained in sodium. If the mixture employed has been such as to melt, it will have prevented a free disengagement of the gases. how these are to be had. To Obtain Pure Alumina.-Eight and a-half parts, by weight, of the sulphate of alumina of commerce for every required part, by weight, of pure alumina, are dissolved in an equal weight of water, and precipitated by a concentrated and boiling solution of acetate of lead in slight excess, and the smallest possible quantity of tartaric acid is added to the liquor, which is separated by decantation, to prevent the precipitation of alumina. The acetate of alumina is then supersaturated with ammonia, and the ammoniacal solution, after being treated with hydrosulphuret of ammonia in a closed vessel, is placed in a stove having a temperature of from 122° to 140° F. This determines the precipitation of the sulphurets of iron and lead, which are removed first by decantation, and then by filtering, but without washing the filters. The clear and slightly-yellow liquor, which consists of acetate and tartrate of alumina combined with ammonia, and some hydrosulphuret of ammonia, is rapidly evaporated and carbonised in an earthen crucible. The residual mixture of alumina and carbon is made into a paste with oil, and strongly calcined to expel the sulphur, due to a little sulphuric acid which remains in the alumina, the whole of it not having been separated by the acetate of lead. To Obtain the Aluminium.-From 3000 to 5000 grains of chloride of aluminium are placed in a tube of glass or porcelain, about one and a-half inches interior diameter, and are insulated by two plugs of asbestos. Hydrogen, purified and dried by being transmitted through sulphuric acid and chloride of calcium, is sent through the tube; and while it is passing, the chloride of aluminium is gently heated by a few coals, to drive by the action of the air on the chloride, and also the away any hydrochloric acid which may have been formed chlorides of sulphur and silicium which are invariably To Obtain Pure Chloride of Aluminium.-present in small quantities. Sodium, previously crushed Some of the mixture of alumina and carbon, just mentioned, is introduced into a porcelain tube that has been fitted with another tube, and is heated to redness in a current of dry chlorine. Chloride of aluminium sublimes, and is removed from the tubes in compact masses, which are composed of very beautiful crystals, that are either colourless or slightly tinged with yellow. If, however, from the impurity of the materials, this chloride is not between two pieces of dry filtering paper, and placed in a boat, is then introduced into one end of the tube while it is still full of hydrogen, and is melted. The chloride is at the same time heated so as to make it rise in vapour, that it may come in contact with the sodium, and be decomposed; and when the sodium has disappeared, and the chloride of sodium that has been formed is saturated with chloride of aluminium, the process is complete. An incandescence which occurs is easily regulated. The boat being taken from the tube, the mixed chlorides, in which the globules of aluminium are suspended, are removed by dissolving in water, and the globules, covered up in a porcelain crucible either with mixed chlorides of aluminium and sodium or with common salt, are fused together by a strong heat. This process answers still better on the large scale; but, instead of the porcelain tube and boat, two cast iron cylinders connected by a smaller tube of iron are employed. The anterior cylinder contains the chloride of aluminium; the posterior, sodium in a tray; and the iron tube, kept at a temperature of from 400 to 500° F., scraps of iron to separate any of that metal which may rise with the vapour of chloride of aluminium, by changing it from volatile per- to fixed proto-chloride. On Aluminate of Baryta and Pure Alumina Salts for Industrial Purposes, by M. GAUDIN. ON commencing my researches I believed, with all other chemists, that aluminate of baryta was insoluble like the aluminates of lime, magnesia, or zinc. The circumstances which led to the rectification of this erroneous impression are sufficiently interesting to deserve being made known. A manufacturer, ignorant of the most simple rules of chemistry, had a fixed idea that chloride of barium could be transformed into baryta simply by the action of aqueous vapour. He engaged my services to put his idea to the proof. This task appeared to me all the more difficult from the fact that, chloride of barium being fusible at red heat, it would be necessary to force Ersted, who was the first to form chloride of the vapour through a liquid; however, I procured some aluminium, is said to have obtained that metal by heat-earthen syphons, hoping, meanwhile, to find a solution ing the chloride with an amalgam of potassium, rich in the latter, and driving off the mercury from the resulting amalgam of aluminium by heat. Aluminium may also be procured from cryolite, a mineral which exists abundantly in Greenland, though it is found only in small quantities elsewhere. It is a double fluoride of aluminium and sodium, and may be produced artificially by adding hydrofluoric acid in excess to calcined aluminium and carbonate of soda, so as to produce Then evaporating, and fusing the result. Both the native and factitious cryolite give aluminium with sodium, and with the galvanic current. The latter, with a mere mixture of aluminium and fluoride of sodium, would afford only sodium and fluorine. It occurred to Rose that, on account of the deliquescence and volatility of the chlorides of the alkaline metals, and the necessity, when they are employed, of preventing any excess of atmospheric air, it would be better in the reduction of aluminium to use a fluoride of that metal combined with an alkaline fluoride; and he proposed to use cryolite, but was deterred by its scarcity at that period. To obtain aluminium in this way, finely powdered cryolite and sodium are placed alternately in layers in cast iron crucibles, the whole being covered with a good thickness of chloride of potassium as a flux. The crucible is then carefully closed with a porcelain cover, and raised to a red heat for half an hour; after which, the calcined matter having been softened with water, it is broken down in a porcelain mortar. The larger globules of aluminium are easily separated mechanically; the smaller, by dissolving away the mass in which they are imbedded with nitric acid without heat. The globules are fused, as before, under the mixed chlorides or common salt. Without this the slight coating of oxide on their surface would prevent their union. When common salt alone is used a higher temperature is required. The aluminium obtained from cryolite almost always contains silicium, and even iron; and the product is not abundant, since 10 of cryolite and 4 of sodium give only o'5 of aluminium. Kose attempted also to procure aluminium by placing the mixed chloride of aluminium and sodium in alternate layers with sodium; but the results were not satisfactory. (To be continued.) to this problem by experimenting upon chloride of barium mixed with an infusible matter, serving as a support, and capable of playing the part of an energetic acid, and displacing hydrochloric acid. This I had no difficulty in finding; I used from the first calcined alumina, which, under this treatment, served as aluminic acid, and by this means I sought to produce an insoluble aluminate of baryta susceptible ultimately of decomposition, by prolonged boiling, into hydrates of alumina and baryta. Aqueous vapour, passing through a granular mixture of alumina and chloride of barium heated to redness, produces, in fact, an abundant disengagement of hydrochloric acid; and the fritt treated by boiling water, and filtered, gives a colourless, limpid, and highly alkaline liquid, precipitating abundantly with sulphuric acid and sulphates. This I believed to be the baryta I was, searching for; but was surprised to find that the liquid yielded an abundant precipitate with weak nitric and hydrochloric acids. The liquid held aluminate of baryta in solution, and this aluminate, though less soluble, should henceforth be classed with aluminates of soda and potash, just as baryta itself is less soluble than soda and potash. In fact, the aluminates of soda and potash diluted with water produce no precipitate with soluble salts of baryta. Aluminate of lime, on the contrary, is so insoluble that lime water poured into a solution of aluminate of baryta determines in it, after a few seconds, a brilliant precipitate of aluminate of lime; so that, by adding to the fritt, before boiling it, milk of lime in excess, the filtered liquid issues a solution of hydrate of baryta perfectly free from alumen. Chlorine of barium being too expensive, I substituted for it, in a series of successive experiments, sulphate of baryta, a mixture of sulphate of baryta, Provençal ferruginous alumina, and charcoal, previously submitted to the action of aqueous vapour in excess. The fritt, treated by boiling water, also produced a limpid, colourless solution, yielding no indications of iron or of sulphocyanide of potassium, or sulphide of barium tested by acetate of lead, resembling, in this respect, soluble aluminate of baryta. By operating in this way, the sulphuric acid of the attacked sulphate of baryta is drawn away by the vapour in the form of sulphide of carbon, sulphur, sulphurous acid, and sulphuretted hydrogen gas. Crystallised sulphur is often deposited in the receiver, together with a large quantity of milky water, a real milk of sulphur which filters through paper perfectly, without any change in appearance. CHEMICAL NEWS, June 21, 1862. On the Colour-tests of Strychnia. This milk of sulphur, which is perfectly free from alkali, may one day, perhaps, be employed in place of flour of sulphur, if not for agricultural purposes, on account of the difficulty of transport, at least in medicine, because, being sulphur in a nascent state, it doubtless possesses great energy of action. It is almost impossible to obtain pure salts of alumina with mineral acids for base, because hydrate of alumina being precipitated from alum, free from iron, this alumina necessarily includes a portion of the saline liquid in which the precipitate takes place; little balls are formed, from the interior of which no washings will eliminate the saline liquid. It is otherwise with soluble aluminate of baryta; for, by adding to it the exact amount of sulphuric acid required to precipitate the baryta in the state of sulphate, all the alumina is precipitated at the same time; then, by the addition of an excess either of sulphuric, nitric, hydrochloric, or acetic acid, the sulphate of baryta remains on the filter, while the pure salts of alumina pass through it in the form of a limpid solution, which, when suitably evaporated, yields. aluminous salts free from all foreign bodies.- Comptes Rendus. PHARMACY, TOXICOLOGY, &c. On the Apparent Difficulty of Detecting Strychnia in the Presence of Morphia-Discovery of a more Powerful Reagent for Strychnia, by JOHN HORSLEY, F.C.S., Analyst for the County of Gloucester. THE first part of the title of this paper has reference to that of Dr. Reese, contained in the CHEMICAL NEWS for June 7. It is very true, as stated by Dr. Reese, that morphia in excess has the power of preventing the effect of chemicals upon strychnia, as ordinarily practised; but the difficulty of detecting it is more apparent than real, all that is necessary being (if the two alkaloids have really been extracted from a dead body) to adopt the method of precipitation of strychnia by the addition to the concentrated aqueous or neutral solution of a few grains of neutral chromate of potash, as suggested by me at the British Association for 1856, aiding the formation of the golden-coloured crystalline precipitate by brisk agitation for a minute or so with a glass rod, then carefully decanting the supernatant liquor containing the morphia (the chromate of which is longer forming); or it may be passed through a very small filter, and the chromic salt of strychnia collected for experiment with strong sulphuric, the merest particle of the salt being sufficient. Under the microscope, the crystals of chromate of strychnia are in the form of little golden-coloured stars; but the corresponding salt of morphia is that of little round granules, with a dark ring on the outside. As a matter of course, these latter, when touched with sulphuric acid, turn green, and so, when in excess, have the effect of masking the reaction of strychnia, which remains passive. As regards the new reagent, that is, the nitroprusside of sodium,-which I used quite by chance the other day, and was astonished at the result, a comparison between it and the bichromate of potash is immensely in favour (where no other alkaloid but strychnia is present) of the nitroprusside, the extreme limit of detection being 1000ooth; indeed, 75,000 is quite marked, but the bichromate scarcely reaches 3000. There is also a greater degree of intensity as well as persistency of colour, nor is there any disposition to that greenness as observed in 341 the reduction of chromic acid; and, as far as I can see, it is entirely free from objection, and commends itself as the test par excellence. It is useful as a precipitant of strychnia, the crystals being in the form of very long spiculæ, and sometimes needles, which strike a splendid colour with sulphuric acid. I arrived at the test figures thus:-1 grain of strychnia was first dissolved in 100 of water. Of this solution, I drop was added to 999 of water; a fragment of nitroprusside was then thrown in, and agitated till dissolved. Of this mixture, drop was let fall into a small whiteware dish, and dried at a steam heat, and on cooling the colour was developed by drawing across the spot a glass rod dipped in sulphuric acid. On the Colour-tests of Strychnia, as Modified by the Presence of Morphia, by ROBERT P. THOMAS, M.D., Professor of Materia Medica in the Philadelphia College of Pharmacy. DURING the last few years the attention of the profes sion has been attracted to the consideration of the various means which have been recommended for the detection of strychnia in cases of poisoning by that powerful agent; and some of the ablest minds in Europe, and of this country, have contributed the results of their labours to the common stock of knowledge on this important point. Having received a thorough investigation from such hands, and its relations traced in almost every possible combination or association, and the test of its presence-both physiological and chemical-having been proved to be alike clear and distinctive, it would appear probable that little more could be added towards the perfection of its history. Nevertheless, a question of great moment has recently arisen, as to the possibility of detecting it at all, if the poison should be associated with an equal, or a greater quantity of morphia, or a salt of morphia in the presence of an organic fluid. The property, referred to morphia when combined with organic matter, of preventing the detection of strychnia by colour-tests, will, if confirmed, afford a satisfactory explanation of the difficulty experienced by Drs. A. S. Taylor, and G. Owen Rees, in their examination of the viscera of J. P. Cook, as elicited on the celebrated trial of William Palmer for his murder, in May, 1856. They could not detect a trace of strychnia, notwithstanding the symptoms antecedent to Cook's decease pointed unequivocally to this alkaloid as the fatal agent. If not decomposed, it must have been masked by the presence of morphia, as Mr. Bamford, the attending physician, administered half a grain of this narcotic each night for three successive nights previous to his decease. The circumstances of this trial, and the experiments, described in the papers referred to, furnish an imperative reason for a further investigation of the subject; as the suicide or murderer can destroy all traces of his work, by simply combining an excess of morphia with a poisonous dose of strychnia. The former will not delay the fatal action of the latter, but, on the contrary, will rather aid it. With the view of determining the important question, whether strychnia is actually decomposed when treated with test-agents in the presence of morphia, or whether it is merely masked by such presence, I have performed more than a hundred experiments, of which an account of a few of the most valuable and satisfactory is now submitted. Premising that, in the examination of minute portions of strychnia, success or failure depends entirely upon the care given to the details. In all of my experiments I employed crystals of the pure alkaloids and of their salts. The "colour-tests" referred to in this paper, are those furnished by bichromate of potassa, or by the ferricyanuret of potassium (red prussiate of potassa), when added to a portion of strychnia previously dissolved in a drop of strong sulphuric acid. The discrepancies in the results of the published experiments of different observers depend, I think, in a great measure, on their diverse modes of procedure, and therefore I feel justified in giving a precise account of The Mode of Testing.-In every instance the material to be tested was employed in the solid form, such as the pure alkaloids or their salts. If it existed in solution, it was reduced to a solid consistence by evaporation in a test capsule, spontaneously, or by a very gentle heat. Having thus procured a solid substance, a small portion of it was placed upon a white plate, a drop of strong pure sulphuric acid was added, and trituration was carefully made with a glass rod until the substance was dissolved. Then a small quantity of powdered bichromate of potassa, or of powdered ferricyanuret of potassium, was deposited on the plate, near the acid mixture but not touching it, and to the powder a minute drop of water was added-just enough to partly dissolve it-and then, with a pointed glass rod, a little stream was drawn from each of the solutions in such a direction as to cross each other. Immediately at the point of intersection the play of testcolours was beautifully manifested. When the bichromate was employed, the sequence of colours was blue or violet, instantly changing to purple, then gradually becoming red, and finally greenish-yellow. When the ferricyanuret was used, the colour was a rich bluishpurple, changing rapidly to a light rose-red. It is important to proportion the sulphuric acid to the amount of alkaloid, avoiding an excess beyond what is necessary to its perfect solution; and, therefore, it is better to take the acid out of the bottle by a pointed glass rod, rather than to drop it from the lip. The first series of experiments was instituted for the purpose of determining how far pure morphia or one of its salts, when combined with strychnia, would prevent the manifestation of the colour-tests. Experiment 1.-Accordingly, equal weights of the pure alkaloids were rubbed together in a mortar and tested; next, one part of strychnia to three parts of the sulphate of morphia; then one of strychnia to four of the acetate of morphia; then one of strychnia to eight, and, finally, one to twenty parts of the sulphate of morphia. In each case the result was entirely satisfactory; the colour-tests flashing out with more or less distinctness, in proportion to the relative quantity of morphia, as soon as the margins of the two solutions on the plate came in contact. As intimated above, one solution was made by rubbing the powdered bichromate with a drop of water, the other by triturating a portion of the morphia and strychnia with a drop of sulphuric acid, being careful to use just sufficient acid to insure a perfect solution. I did not consider it necessary to carry this experiment any further, because, in a case of poisoning in which the morphia should be twenty times greater than the strychnia, the fatal result and the attendant symptoms would probably be more characteristic of the action of the former than of the latter, and our experiments would be devoted to its detection, (To be continued.) June 21, 1862. INTERNATIONAL EXHIBITION. CLASSES III. AND IV. (Continued from page 327.) Substances Used as Food, and Animal and Vegetable Ir any sceptical oilman entertains a doubt of the pos- The articles in Classes II., III., and IV. in the French exhibition are placed in a particularly bad light,—so bad that in some instances it is difficult to see the things in the cases. Those, however, in Class III. which can be seen, look remarkably good, and it is hard to pick out any for especial praise. The truffles, for which our neighbours are famous, appear in great numbers, but do not look inviting. In 327 there are lobsters preserved in their shells, which look very fresh and good. The tobaccos exhibited by English houses do not call best looking, we should select that shown by Mr. of these we have had no opportunity of judging, and CHEMICAL NEWS, Royal Institution of Great Britain. In Class IV. there is one article in which English manufacturers hold an indisputable pre-eminence, and that is soap. If proof of this were needed, it is to be found in this exhibition. The case which will perhaps attract most attention is that of Messrs. Williams and Son (953). This firm exhibits all kinds of soap,-the fine curd used by silk dyers for ungumming silk, the coarser sorts used by cloth millers and wool spinners, and the various kinds used for household purposes. The interest of the case, too, is increased by samples illustrative of the manufacture, showing, for example, the quantity of kitchen-stuff, water, and alkali which go to make up a pound of mottled soap, and the tallow, rosin, and alkali for a pound of common yellow. Knight and Sons (924) and Cowan and Sons (917) exhibit fine blocks of various kinds. The last-mentioned firm also exhibit (501) a series illustrating the manufacture of animal charcoal from bones, showing first the extraction of the grease for making soap, and the subsequent steps for the preparation of the charcoal for sugar refining, a process they carry on in conjunction with soap making. In 916 and 943 are also shown fine specimens of soaps, nor should the display of the West of England Soap Company (950) be passed without notice. Fancy soaps are also well represented in the cases of Mr. Cleaver (1168) and Messrs. Yardley and Statham (1195). If the English visitor wishes to gratify his national pride, he may take a glance at the specimens in this class exhibited in the French department. He will there find several samples of the article whose acquaintance he may possibly have made on the occasion of some visit to Paris,-a hard, chalky, uncomprising substance, which no efforts would induce to make a lather, and which left a smell on his hands and face that the amount of water provided for his use could never rinse away, a smell that is but too plainly perceptible in this Exhibition at some distance from the cases in which the soap is exhibited. Spain shows what we presume is genuine Castile soap, but which is no further remarkable. Next to soap come candles, and on this article we may also congratulate our countrymen. The case of Price's Patent Candle Company (936) is one of the most elegant in this department, and the articles displayed fully sustain the reputation of the Company. The visitor will notice the specimens of palm oil in different stages of treatment, and the beautiful results obtained by the distillation process. He may perhaps be a little puzzled at Case 911, in which Mr. Bauwens exhibits palm oil distilled by sub-heated steam, the exact meaning of which term we should be glad to have explained. Case 926, shown by Messrs. Langton and Co., will be sure to attract notice for the beautiful specimen of spermaceti it contains, and which is alone worth going to the Exhibition to see. The case is further noticeable for samples of spermaceti in different stages of preparation, which will give an unlearned visitor a clear notion of the method used for separating the pure substance and the oil from the head and body matter. The case of Messrs. Ogleby and Co. is hardly less remarkable for the beauty of the spermaceti, here crystallised in a form resembling the young, soft antlers of a stag, or the extremities of the branches of a sumach tree. The specimens of stearic acid in this beautiful. also very Paraffin, too, is well represented. In 918 Messrs. Field and Co. show specimens looking very bright and hard. Several other cases contain samples of great excellence, and we should hope this article would soon be in common use. Wax candles are exhibited by a few houses, in some instances beautifully coloured, and of elegant and fantastic case are 343 forms; but the use of these candles, we presume, is passing away before the cheaper and equally well-looking articles, with higher illuminating power, which modern science has called forth. PROCEEDINGS OF SOCIETIES. ROYAL INSTITUTION OF GREAT BRITAIN. A Course of Six Lectures on Some of the Chemical Arts, with LECTURE III. (Thursday, May 22, 1862.) Processes. IN my last lecture I brought before you various colours produced by coal-tar which had recently been employed in the art of calico printing. I also at the same time mentioned to you that the discovery of these colours from coal-tar was likely very materially to alter the whole art of calico printing, which, in its present aspect, involves some beautiful applications of science. You will readily understand that, after we have gone over the preliminary processes connected with this art. was "Robes "Calico printing" is a generic term. Although the term "calico" is used in it, it embraces all the arts of making dresses with coloured patterns, whether they are manufactured from silk, from woollen, from linen, fron, cotton, or from any mixture of those materials. It is, therefore, merely a generic term, describing the ordinary dresses which receive designs by means of impression and not by mere dyeing. The name "calico printing originally derived from Calicut, in Hindostan, where the art of impressing cotton with colours was carried out to a great extent, although the same art had been employed long before in Egypt as regards linen. The skill of the printer consists in placing as many colours as possible upon the tissue, and deriving them from one dyeing material; for all his supplementary processes are merely confessions of his inability to produce all the colours which he desires from one material. Pliny gives us a description of the manner in which the ancient Egyptians practised the art, and his account is so excellent that I could not possibly give you a better explanation of the art of the present time. I therefore quote it in full. and white veils," says Pliny, "are painted in Egypt in a wonderful way. They are first imbued, not with dyes, but with dye-absorbing drugs, by which they seem to be unaltered, yet when they are immersed for a little while in a boiling caldron they are found to become painted. Yet, as there is only one colour in the caldron, it is marvellous to see many colours imparted to the robes in consequence of the influence of the excipient drug. Nor can A caldron which would merely the dye be washed out. confuse the colour of cloths previously dyed is thus made to impart several pigments from a single dye stuff, painting as it boils." You will find as I proceed in the description of the art that this latter term of Pliny's, "painting as it boils," is a true description of the art as now practised. Since the time of the ancient Egyptians the practice of calico printing has made enormous strides, and yet it would be impossible in the present day for any one to write a more concise or accurate description of the art even as now practised, than Pliny has done of the condition of the art of the old Egyptians. Although the principles upon which the art was carried out were known in former times, yet its resources have vastly improved. |