"I am ready to preach, argue, write, but I will not constrain any one; for faith is a voluntary act. Call to mind what I have already done. I stood up against pope, indulgences, and Papists; but without violence or tumult. I brought forward God's word; I preached and wrote, and there I stopped. And whilst I laid me down and slept, or chatted with Amsdorff and Melancthon over our tankard of Wittemberg beer, the word I had preached brought down the power of the pope to the ground, so that never prince or emperor had dealt it such a blow. For my part, I did next to nothing; the power of the word did the whole business. Had I appealed to force, Germany might have been deluged with blood. But what would have been the consequence? Ruin and destruction of soul and body. Accordingly, I kept quiet, and let the word run through the length and breadth of the land. Know you what the devil thinks, when he sees men resort to violence to spread the gospel through the world? Seated behind the fire of hell, and folding his arms with malignant glance and horrid leer, Satan says, 'How good it is in yonder madmen to play into my hands!' But only let him see the word of the Lord circulating, and working its way unaided on the field of the world, and at once he is disturbed at his work, his knees smite each other, he trembles, and is ready to die with fear."-From D'Aubigné.

ALUM.

ALUM is a substance occasionally used in domestic economy and in medicine, but is more extensively employed in the arts. It is a substance well known to all our readers; and from this circumstance, as also from its many uses, we may with propriety introduce a few remarks on its chemical constitution, properties, and manufacture.

Alum is composed of that substance which we call alumina, sulphuric acid, and potash; the last-mentioned principle being sometimes replaced by another alkali, ammonia. The alum of commerce is said to yield by analysis the following substances in the proportions affixed-sulphuric acid, 34.33; alumina, 10-86; potash, 981; water, 45.00. Pliny, and other of the ancient writers, speak of alum; and it might, consequently, be supposed, that they were acquainted with the substance so called by us. There

is, however, abundant evidence, that the alum of the ancients was a natural substance, and, in fact, a vitriolic mineral. Mr. Barlow, speaking on this subject, says, "The alum of the ancients was a natural formation; and we accordingly find no account of alum and vitriol works, in any Greek or Roman author, except what is mentioned by Pliny, who states, that blue vitriol was made in Spain by the process of boiling; and this circumstance he considers as the only one of its kind, and so singular, that he was of opinion no other salt could be obtained in the same manner. Besides, every thing related by the ancients of their alum agrees perfectly with natural vitriolic substances." The same writer further remarks, "The celebrity which the ancient alum had, as a substance extremely useful in dyeing and medicine, was entirely forgotten, when the alum of the moderns became known; but this celebrity was again revived, when it was discovered that real alum could be made from vitriolic minerals, or that where the latter are found, there are generally minerals which abound with it. In many of these places alum works have, in the course of time, been erected; and this circumstance has served, in some mea→ sure, to give rise to the opinion that the alum of the ancients and that of the mo→ derns are the same salt; because, where the former was found in ancient times, the latter has since been procured by a chemical process."

At what period the manufacture of alum was discovered cannot now be de→ termined, but there is historical evidence, that for some centuries past it has been produced in the east, and brought by merchants into Europe. It is probable that it was first manufactured at Roccha, in Syria, and hence called Roch alum. From this place, as also from Foya Nova, near Smyrna, it was brought by the Ge noese into Europe, for the use of the dyers. This was probably in the early part of the fifteenth century; and soon after that period the alum works of La Tolfa, about six miles from Civita Vecchia, were established, and the pope pro→ tected them, by prohibiting the importation from eastern countries.

In the reign of Elizabeth, sir Thomas Chaloner established alum works at Whitby, in Yorkshire, for which he was excommunicated by pope Pius 11., who was anxious to enjoy all the advantages to be derived from the trade. The hard

small quantity of very cold water, the colouring matter is disposed of, or at least after the process has been once or twice repeated.

There is now but one process more to fit the substance for the market, and that is crystallization. The alum, properly washed, is placed in a leaden pan, with sufficient water to dissolve it at a boiling heat. When in a liquid state from heat, it is poured into a kind of cask, where it is left to cool slowly, and crystallize. In eight or ten days the crystallization is completed, and the vessel in which the substance is contained is taken to pieces, and the apparently solid mass of alum removed. The centre of the mass, however, contains the mother water, which is made to run into a cistern, where it is again used in subsequent manufactures. The large mass of alum, being broken into pieces, is dried, and is then fit for the market.

The uses of alum in the arts are very great. It is of much service in the preparation of some of the finer sorts of skins, such as those of the hare, rabbit, and kid. By its means they may be rendered durable, flexible, and more incorruptible than those skins which are prepared in the tan-yard. To dyers it is invaluable, as it forms the basis of some of their principal mordants, or liquors used to fix their colours on cloth. One of the principal of these we will endeavour to describe; and as its preparation is peculiar and interesting, we will detail it.

The acetate of alumina, which is the mordant most used, is prepared from the sulphate of alumina, or alum of commerce. The alum is dissolved in water, and a similar portion of the sugar or acetate of lead. When both the solutions are clear, they are mixed together, and a chemical decomposition takes place. A white precipitate will be immediately formed, and this, upon analysis, would be found a sulphate of lead, and on account of its density, quickly subsides, leaving a clear liquid, which is the acetate of alumina, and the mordant most commonly used by the dyer. It is principally employed in fixing the vegetable colours upon woollens and other cloths.

Alum has the property of hardening casts of plaster of Paris, and is extensively used for this purpose by those persons who make plaster statues, by house decorators in their ornaments formed of plaster and linseed oil, and by dentists, to harden their surgical models.

We have already stated, that alum is

composed of sulphuric acid, and the earth called alumina, combined with either the alkali, potash, or soda, which is merely added to render the sulphate of alumina capable of crystallization. The earth alumina is a most important ingredient in the manufacture of many colours, especially in the various lakes. These are nothing more than a combination of the colouring matter of the cochineal madder, or some other animal or vegetable substance, with alumina. This may be proved by a very elegant experiment. Let a few grains of cochineal be powdered, and a small quantity of water being placed thereon, add a few grains of the carbonate of potash; raise the temperature of the mixture to the boiling point, in a test tube, or some other convenient glass vessel. Add a small quantity of the solution of alum, and a red carmine-coloured precipitate will be formed, which is, in fact, the lake of commerce. theory of this formation is so interesting, that we shall venture to explain it to our readers. When the solution of alum is mixed with the cochineal and carbonate of potash, the sulphuric acid of the alum combines with the potash of the carbonate, forming a sulphate of potash. An escape of carbonic acid takes place at the same time, and the alumina which is liberated from its combination with the sulphuric acid, combines with the colouring matter of the cochineal, forming a red sediment, which is the lake of commerce. After this precipitation has taken place, the liquid will be of a pale straw colour.

The

In closing this paper, we may mention, for the amusement of the young reader, a method of producing some delicate and interesting ornaments, by the crystallization of the substance of which we have been speaking. If a small osier frame basket, made as open as possible, be twisted round with worsted, and then immersed in a hot strong solution of alum, it will, when cold, be covered with brilliant and well-formed crystals of that substance, and the basket itself will appear as if made of spar, or some other transparent mineral. A pink crystal may be formed, by adding a small portion of archil, or mahogany dye, and a brilliant yellow by turmeric. Of course, any other form may be adopted as well as the basket, and the specimens are not only interesting as pretty ornaments, but also exhibit, to the person who observes the process, the actual workings of nature.

H.

ENGRAVED DRAWINGS.

A NEW process has lately been discovered, by which the means of multiplying drawings are obtained, without the aid of the engraver.

The plate used for drawing upon being blackened, and having a white ground spread evenly over it, that the artist may see his effect, as if he were drawing on paper, every line or dot cut through the white ground will lay bare the black plate beneath, and thus the work will appear as though it were drawn with ink, or a blacklead pencil.

The kind of tool recommended is to all appearance, and in its mode of use, exactly like a common lead pencil. For very bold and free drawing a HHH drawing pencil, sharpened to the point required, will answer the purpose.

The design being thus traced by the artist, either elaborately or otherwise, the plate is subject to the electrotype process, and from it is taken a perfect cast, which must, of necessity, when printed from, transfer to paper a fac-simile of the original drawing.

This branch of art is called by the patentee, Mr. Palmer, of Newgate-street, Glyphography. It appears adapted not APRIL, 1843.

only to professed artists, but to amateurs in general; for a skilfully-sketched portrait or landscape may be multiplied at pleasure, by the parlour fireside, as they have the means of taking the proofs themselves.

One advantage is thus stated by the patentee:

"To engravers in general, the wide field of surface printing has hitherto been entirely closed; and, as regards the present state of that branch of art, there is such a determined demand for 'black and white' effect, that the beautiful sweetness of tone and finish which the line engraver carefully introduces into his work, is rarely, if at all, in requisition. Indeed, owing to the extra labour and skill that are requisite to execute with delicacy cross-hatching upon wood, it is very much, if not altogether, neglected by many engravers. Hence, there is an excess of half-tone or middle tint, as many of our large wood cuts abundantly prove, in their miserably cold and poor effect; which, of necessity, leads the artist to introduce strong contrasts of black and white,' by way of relief. Cross-hatching in wood engraving is, we know, much depreciated, on account of

L

the labour of its execution; but a line engraver is aware that, even on copper, large half-tones or shades, formed by a single line, would spoil his plate, by their inexpressive coldness and want of character. Now, although the bold effect produced by the contrast of 'black and white' may, to a certain extent, be desirable in cuts that are introduced in pages of type, against which they have to maintain impression; yet, there is no reason, (except the requisite labour,) why the softer tones, and more finished effects of line engraving should not be closely imitated in frontispieces and whole page illustrations engraved on wood. By the glyphographic process, this labour is dispensed with; and, although in surface printing we can scarcely expect to equal the delicacy of highly wrought line en

graving, yet the artist may, by aid of this invention, take a decided position between the average merit of wood engraving and elaborate copperplate engraving; besides securing a faithful copy. of his design, to the most minute touch."

The process exhibits an ingenious application of galvanic or voltaic power, for an account of which the reader is referred to the Visitor for 1840 and 1841. The patentee, who has published, at a trifling cost, full particulars of the art, for artists and amateurs, engages to announce, from time to time, for the benefit of all who use his plates, every improvement that may arise, in materials, tools, or methods of using them. The engravings at the commencement and close of these remarks, show the effect produced by the art in its present state.