ARTICLE X.

Some Improvements of Lamps. By James Smithson, Esq. FRS. (To the Editor of the Annals of Philosophy.)

SIR,

It is, I think, to be regretted, that those who cultivate science frequently withhold improvements in their apparatus and processes, from which they themselves derive advantage, owing to their not deeming them of sufficient magnitude for publication.

When the sole view is to further a pursuit of whose importance to mankind a conviction exists, all that can do so should be imparted, however small may appear the merit which attaches to it.

Of the Wicks of Lamps.-The great length of wick commonly put to lamps for the purpose of supplying the part which combus tion destroys, is, on several accounts, extremely inconvenient. It occupies much space in the vessel, and requires an enlargement of its capacity; it is frequently the occasion of much dirt, &c. This great length of wick is totally unnecessary.

Fig. 1.

Fig. 2.

Fig. 3.

Fig. 4.

a

It is advantageously supplied by a tube containing a bit of cotton wick about its own length, or some cotton wool, fig. 1, and at the end of which is placed a stout bit of wick or cotton wool, fig. 2.

This loose end receives a supply of oil from the cotton under it with which it is put into contact, and when it becomes burned, it is easily renewed.

A loose ring of wick may in like manner be applied to the argand lamp. This removes the necessity of the long tube into which the wicks, now used, descend, and thus greatly contracts this lamp in height.

Of Wax Lamps.-Oil is a disagreeable combustible for small experimental purposes, and more especially when lamps are to be carried in travelling. I have, therefore, substituted wax for it. I experienced, however, at first, some difficulty in accomplishing my object.

The wicks of my lamps are a single cotton thread, waxed by

drawing through melted wax. This wick is placed in a burner made of a bit of tinned iron sheet, cut like fig. 3, and the two parts a a raised into fig. 4.

This burner is placed in a china cup, about 1.65 inches in diameter, and 0-6 in. deep. Fragments of wax are pressed into this cup. But great care must be taken that each time the lamp is lighted, bits of wax are heaped up in contact with the wick, so that the flame shall immediately obtain a supply of melted wax. This is the great secret on which the burning of wax lamps depends.

. When the wick is consumed, the wax must be pierced with a large pin down to the burner, and a fresh bit of waxed cotton introduced.

. I employ a wax lamp for the blowpipe. This has, of course, a much larger wick, and this wick has a detached end to it, as above described.

Extinguishing Lamps.-The best way of doing this is to extinguish the ignited part of the wick by putting sound wax on to it, and then blowing the flame out. This preserves the wick entire for future lighting again.

This mode applied to candles is much preferable to the use of an extinguisher, or douters, to which there are many objections.

ARTICLE XI.

On Works in Niello and the Pirotechnia of Venoceio Biringuccio Siennese. By the Rev. J. J. Conybeare.

(To the Editor of the Annals of Philosophy.)

DEAR SIR,

Bath Easton, Oct. 14, 1822,

IN Mr. Ottley's interesting and learned History of Engraving, vol. i. pp. 262 and 270, two accounts are given of the process used in the execution of the ornamental work termed Niello: the former, very short, and evidently inaccurate, from Vasari; the latter from a modern virtuoso (the Count Seratti), whose statement, although more correct, is unsupported by any reference to earlier authorities, not to mention that Seratti himself is (as Mr. Ottley with justice remarks) somewhat wanting both in accuracy and in judgment. It is sufficiently known that the Niello (independently of the esteem in which it was once held, and the real merits and beauty of the works executed in it by Finiguerra and others) has been yet more ennobled by having given birth to the invaluable art of transferring impressions from engraved plates to paper. The following description, therefore, of the mode which seems to have been usually adopted for the compo

sition of the enamel (if we may so call it), as well as for its insertion into the cavities produced by the graver, may not, perhaps, be unacceptable to your readers. It has the merit of coming from an author who lived before the art was yet obsolete, and who seems himself to have been a practical man of considerable intelligence for his day.

"The Niello," he informs us, "is composed by taking one part of pure silver, two of copper, and three of pure lead, which must be fused together, and in that state poured into a longnecked earthenware matrass, half filled with levigated sulphur, the mouth of the vessel is immediately to be closed, and the contents left to cool. The mass which results, when levigated and washed, is ready for the purposes of the artist. The cavities made by the burin having been filled with it, the plate is to be held over a small furnace fed with a mixture of charcoal and wood, taking care to distribute the enamel carefully with a proper instrument. As soon as its fusion has taken place, the plate is to be removed, and when sufficiently cooled is to be cleared by the file, and polished by fine pumice and tripoli."

To the four ingredients here enumerated, the receipt given by Seratti adds a fifth, borax, the use of which is not immediately apparent. A small portion might, perhaps, be put into the crucible containing the alloy, to cover it, and facilitate its fusion, but it could scarcely enter into the composition of the enamel itself.

The Pirotechnia of Biringuccio, from which the above is extracted, is a book of somewhat rare occurrence, and, for that reason, perhaps, has not been noticed as it deserves by those who have employed themselves in tracing the progress of mineralogy and metallurgy. It was first printed at Venice in the year 1540, and, therefore, preceded by 20 years the more splendid volume of G. Agricola, which on subjects immediately connected with mining is unquestionably more copious and instructive. Biringuccio, however, embraces a much wider range, and his work is certainly better calculated to illustrate the state of knowledge at the era of its composition than that of his German successor. The good Italian too manifests, if not so much of erudition, a far more lively play of the imagination. His work is divided into 10 books. The first treats of metals; the second, of semimetals, with some earthy and saline substances; the third, on the assay and reduction of metallic substances; the fourth, on the assay and refining chiefly viû humidû; the fifth, on alloys; the sixth, seventh, and eighth, on the art of casting metals, treating largely on all that concerns bell and cannon founderies; the ninth, on distillation; on the arts of the workers in gold, copper, iron and tin-wiredrawing, gilding; the manufacture of metallic specula; of crucibles, of pottery, and of mortar; the tenth, on nitre, gunpowder, artillery, and fireworks. This abridged table of contents will suffice to give a general

notion of the work. I subjoin a brief statement of such passages as, on a cursory perusal, appeared interesting:

B. 1. Under the chapter "Luoghi de la Miniera," he speaks slightingly of the "charlatanerie" of those who pretend to discover mines by any other than natural indices; his directions, as far as they go, are very sensible. He mentions the custom of baptizing or dedicating the mine by the name of the deity, or of some patron saint. He recommends the driving an adit from the bottom or side of the hill in preference to the older usage of digging downwards from the point where the ore comes to day (algiorno). He mentions a productive mine of copper and lead below Inspruck. C. Dell'Oro. He opposes strongly the dreams and impositions of the alchemists. C. Dell. Argento. Quotes G. Agricola (quere, from what work?) as relating the discovery of a mass of silver ore, in one of the Saxon mines, sufficiently large to make a table and a seat, or stool (tripode). He seems to have been acquainted with the red and grey silver ores, and with the usual modes of roasting and reducing them. C. Del Rame. Italy is in this metal "richissima; " mentions the peacock and grey copper ores, especially the richness of the latter. C. del Piombo. He notices its acquiring weight (from 8 to 10 per cent.) by calcination, which he attributes to the loss of some aerial principle of levity, and illustrates the case by affirming that a dead body weighs more than a living one, in consequence of having lost the animal spirits (spiriti che sustengano la vita). C. De lo Stagno. He confesses never to have seen any tin ores. C. Del Ottone. He speaks almost with rapture of an extensive manufactory of brass carried on at Milan. C. Dell. Argento Vivo. He again ridicules the alchemists with some humour; mentions native cinnabar, and the method of obtaining mercury from its ores by distillation. C. Del Solfo. Mentions the use of sulphur in bleaching. C. Del Antimonio. Speaks of its use in various alloys, and as an external application in medicine. C. Della Margassita. He suspects each of the imperfect metals to have its own marcasite, consisting of sulphureous matter, and the seeds of the metal (materia seconde et menstrui delle concettioni de metalli). The residuum after roasting is good only to colour porcelain or glass, and to cheat the alchemists. Argues against its being entirely "fumosita," (a substance capable of sublimation?) but appears to entertain the belief of his age, that mineral veins grow like organized bodies. C. Del Vetriolo. Describes the manufactory of Roman vitriol, the strongest form of which non Vetriolo ma Cuperosa si chiama." C. Dell Alume di Roccha. Gives a detailed and practical account of its manufactory. Mentions the district of La Tolfa as not likely to be exhausted before "l'ultimo giorno del mondo." C. Del. Arsenico, Orpimento et Risagallo. Mentions the alloys of arsenic with copper, brass, and lead. Its ores come from the Hellespont and Cappadocia. Notices the observation of "li prattici mine

66

rali," that arsenic is mixed with almost all metallic ores, and the opinion that in volatilizing it carries off whatever silver they may contain. C. Della Giallamina, Zaffara, et Manganese. This chapter contains the earliest mention with which I am acquainted of manganese. Its use, both in tinging porcelain and glass, and in rendering the latter colourless, is noticed. The chapters on gems and glass contain little of interest. Those on the assay and reduction of metals are entirely practical, and show an intimate acquaintance with the detail of all the processes then in use. În treating of alloys, he mentions the superiority of English tin.

The alloy for bell metal he states to contain from 22 to 26 per cent. of tin; that for other purposes of casting from 8 to 12. Enters largely into detail on the casting both of artillery and bells. At p. 100, he mentions a singular mode of soldering large bells when damaged, by carrying the curved chimney of a furnace constructed for the purpose in the direction of the fissure, and cementing the edges thus softened by the addition of melted bronze. This is, I suspect, a process never adopted in our bell founderies.

Of the value of his further directions for casting, &c. I am not competent to judge; they appear tolerably full. At p. 109, he mentions, that in the manufactory of bronze, lead was occasionally substituted in part for tin, as being cheaper. C. del Far le Palle di Ferro. He states that cannon balls of cast-iron were first used in Italy, by Charles, King of France, in his attack on Naples, A. D. 1495. He mentions that some added antimony, others copper, and others arsenic, with the intent of rendering the metal more fusible, but objects that it is rendered at the same time more brittle. C. di Formare Rilievi. He appears to have been acquainted with all the modes of casting and modelling now in use. He much praises the ingenuity of a Siennese