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troduction of machinery, great efforts were made on the part of the employers to render themselves independent of hand labour; and the result has been the gradual introduction of cylinder printing. Without entering into the intricate details of the steps by which the art of engraving has been carried to its present high degree of perfection, I shall simply give an outline of the successive improvements alluded to.

Engraving. The first kind of roller used was made by bending a sheet of copper into a cylinder, soldering the joint with silver, and then engraving upon the continuous surface thus obtained.

The second improvement consisted in producing the pattern on copper cylinders obtained by casting, boring, drawing and hammering. In this case, the pattern is first engraved in intaglio upon a roller of softened steel, of the necesssary dimensions. This roller is then hardened and introduced into a press of peculiar construction, where, by rotatory pressure, it transfers its design to a similar roller in the soft state, and the die being in intaglio, the latter, called the "mill," is in relief. This is hardened in its turn, and by proper machinery is made to convey its pattern to a full-sized copper roller. This improvement alone reduced the cost of engraving on copper rollers many hundreds per cent.; and, which is of far greater importance, made practicable an infinite number of intricate engravings which could never have been produced by hand labour applied directly to the roller.

A further improvement was made by tracing with a diamond on the copper roller, covered with varnish, the most complicated patterns by means of eccentrics, and then etching.

The combination of mill engraving with the tracing and etching processes naturally followed, adding immensely to the resources of the engraver and printer in production of novel designs.

Another development of this art is the tracing of patterns on the surface of rollers, which has been effected

by machines constructed on the principle of the pentagraph. Although this invention dates from 1834, still it is only of late years that it has been successfully applied.

But if mechanical art has greatly assisted the engraver, chemistry has rendered him equally important services, by enabling him to abandon costly and cumbrous modes of impressing by force the designs on the cylinder, substituting for them a great number of etching processes. By some of these processes, as by every other addition to the resources of the engraver, an entirely new and beautiful class of engraving is produced, unattainable by any other known means.

A very recent improvement is highly interesting in a scientific point of view. It is the application of galvanism to the diamond tracer. By combining the galvanic action with the eccentric motion, most beautiful and delicate engravings can be produced. This is effected by tracing the pattern with a varnish on a zinc cylinder, which is so placed in the engraving machine, that as a needle passes over its surface, and comes in contact with the zinc, the galvanic current is established, and by simple machinery, causes the diamond to trace the corresponding pattern on the copper roller. The communication is so rapid and so precise, that this invention of Mr. Gaiffe, of Paris, bids fair to produce very important results. Galvanism is also made use of, for producing effects on roller surfaces by depositing copper thereon.

To give an idea of the extraordinary influence which the introduction of machinery and improvements in engraving have had in cheapening the cost of printed calicoes, I may state, that large furniture patterns, such as are required for Turkish, Egyptian, and Persian markets, into which 16 colours and shades enter, would have cost formerly from 30s. to 35s. per piece, because they would have required 16 distinct applications of as many different blocks, and would have occupied more than a week in printing, whereas the same piece can now be printed in one single operation, which

takes three minutes, and costs 5s. or 6s. So rapid is the progress of one branch of manufacture in connection with another, that it has only recently been possible to produce the rollers capable of performing this operation, that is to say, cylinders of copper 43 inches in circumference, by 44 inches long. For light styles of printing, the time required to print a piece of 36 yards is not more than one minute.

CHEMISTRY. But the discovery which has exercised more influence than any other on the progress of calico printing, is the application of chlorine gas as a bleaching agent. Previously to the employment of this gas (chiefly as bleaching powder) the imperfect bleaching of a piece of calico required six weeks; and as it had to be exposed to the action of the atmosphere, a large surface of land was required. Further, at that time, bleachers had to use potashes imported from Canada; whereas, at the present time, thanks to the progress of chemical knowledge, not only is soda-ash manufactured in this country, but by the application of bleaching powder, calicoes are much better bleached in 24 hours than they were formerly by a six weeks' exposure to the atmosphere; and even when an extra cleaning and whiteness is required, as for madder goods, only two days are necessary. The aid of machinery renders possible the continuous process; that is to say, several hundred pieces of grey calico are sewn together, end to end, and made to pass from one operation to another, without any pause, until they are bleached. So rapid and economical is this method that the cost of bleaching a piece of calico does not exceed one or two pence. Chlorine, again, renders a great service to the calico printer, by enabling him, after his madder goods have been produced and soaped, to obtain fine whites without the necessity of exposing them for several days in the meadows to the action of the atmosphere. In fact the discovery of garancine and alizarine, and their application to calico printing, have facilitated the production of

madder styles, at very low cost, as the whites of such goods require no soaping, and only a little bleaching or cleaning powder.

Cotton has this peculiarity, as distinguished from wool and silk, that it will not fix any organic colour, excepting indigo, without the interposition of a mordant, which is generally a metallic oxide or salt. The two most important discoveries in connection with this necessity of calico printing were; first, that made in 1820, by Mr. George Wood, of Bankbridge, who found out the means of preparing calicoes with peroxide of tin, which enabled printers to produce a large variety of prints called steam goods; and secondly, that of Walter Crum, Esq., F.R.S., who, in a paper presented to the British Association, at Aberdeen, in 1859, showed that the tedious process of ageing madder mordants for three or four days, might be dispensed with, by passing the goods during a quarter of an hour through a moist atmosphere, at a temperature of 80 to 100 degrees, where the mordants absorb the required quantity of moisture, and then rapidly undergo the chemical changes necessary to fit them for producing the black, purple, lilac, red, pink, and chocolate colours, which the madder root will yield immediately in the dyebeck, according to the nature of the mordant previously fixed in the cloth.

As it is impossible, in the brief space of an hour to convey an idea how various colours are produced on prints, I shall confine my remarks to illustrating the interesting fact that abstruse science has brought to light various substances, which have lately proved valuable accessories to the resources of the calico printer. Thus, Dr. Prout, some thirty or forty years ago, made the curious discovery, that uric acid possessed the property of giving a beautiful red colour, when heated with nitric acid and then brought into contact with ammonia. The substance thus obtained was further examined by Messrs. Liebig and Wohler, in a series of researches which have been considered as amongst the most

important ever made in organic chemistry; and this substance they called Murexide. In the course of these investigations, they also discovered a white crystalline substance called Alloxan. For twenty years both these substances were only to be found in the laboratory; but in 1851 Dr. Saac observed that alloxan, when in contact with the hand, tinged it red. This led him to infer that alloxan might be employed to dye woollens red; and further experiments convinced him that if woollen cloths were prepared with peroxide of tin, passed through a solution of alloxan, and then submitted to a gentle heat, a most beautiful and delicate pink colour resulted. Subsequently murexide was employed and applied successfully by Mr. Depouilly, of Paris, to dyeing wool and silk, and to printing calicoes, by the aid of oxide of lead and chloride of mercury as mordants; but the great obstacle to its extensive use was the difficulty of obtaining uric acid in sufficient quantity for its manufacture. The idea

8000 occurred to chemists to extract it from guano; and this is the curious source whence the chief supply of uric acid is obtained, and which enables Edmund Potter, Esq., and other printers, to produce the colour called Tyrian purple.

Another example will be found in the successive scientific discoveries which have led to the production of the recently popular colour, Mauve. Lichens, which have been the subject of extensive researches on the part of Robiquet, Heeren, Sir Robert Kane, Dr. Schunck, and especially of Dr. Stenhouse, have yielded to those chemists several new and colourless organic substances, which, under the influence of air and ammonia, give rise to most brilliant colours, and amongst these are orchil and litmus. Dr. Stenhouse, in a most elaborate paper, published by the Royal Society in 1848, pointed out two important facts; first, that the colour-giving acids could be easily extracted from the weed by macerating it in lime water, from which the colouring matters were easily separated by means of

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