who did not write till 1681, has introduced particularly into his dictionary matita rossa, nera, and also lapis piombino; and says that the last-mentioned is an artificial production, which gives a leaden colour, and is employed for drawing. It is evident therefore that the author here alludes to plumbago, which was then very common. But when Bottari says1 that artists first began to use red and black chalk in the time of Vasari, whereas lapis piombino only was employed before that period, he bas named plumbago, commonly used in his time, instead of the metallic pencil which was called stile. If I am not mistaken, the Italians have no proper appellation for black lead, but call it sometimes matita and sometimes piombino. [Great difficulty was formerly experienced in protecting the Borrowdale black-lead mine from robbery. At present, the treasure is protected by a strong building, consisting of four rooms upon the ground floor; and immediately under one of them is the opening, secured by a trap-door, through which workmen alone can enter the interior of the mountain. In this apartment, called the dressing-room, the miners change their ordinary clothes for their working-dress as they come in; and after their six hours, post or journey, they again change their dress, under the superintendence of the steward, before they are allowed to go out. In the innermost of the four rooms two men are seated at a large table, sorting and dressing the plumbago, who are locked in while at work, and watched by the steward from an adjoining room, who is armed with two loaded blunderbusses. In some years the net produce of the six weeks' annual working of the mine has, it is said, amounted to from 30,000l. to 40,000l. An inferior kind of plumbago is imported from Mexico and Ceylon; and a composition with which more common pencils are manufactured is made of a mixture of plumbagopowder, lamp black and clay. A useful and convenient application of the black lead in the form of minute cylinders which slightly projected from a cylindrical cone, and which was fitted to a pencil-case, was patented in 1822 by Mr. Mordan, and has come into general use the cylindrical form of the plumbago is produced by 1 In his observations on Vasari, iii. p. 310. passing square strips of it through holes in a ruby, somewhat in the manner of wire-drawing. It is stated that the supply of plumbago from the Cumberland mine is almost exhausted; fortunately, a process has been devised by which the same firmness and equality may be communicated to the powder by compression. This is effected by carefully washing and grinding the dust obtained in sawing plumbago into thin plates, sifting it through spaces less than the 300th part of an inch, and placing it under a powerful press, on a strong die or bed of steel, with air-tight fittings. The air is then pumped from the dust, and while thus freed from air, a plunger descends upon it and it becomes solidified. The power employed to perform this operation is estimated at 1000 tons, several blows having been given, each of this power. This process was invented by Mr. W. Brockedon, the talented draftsman of Alpine and Italian scenery.] SAL-AMMONIAC. Ir is not very probable that Dioscorides, Pliny, and others who lived nearly about the same time, were acquainted with sal-ammoniac, or mentioned it in their works; for no part of mineralogy was then so defective as that which is the most important, and which treats of salts. The art of lixiviating earths and causing saline solutions to crystallize was then so little known, that, instead of green vitriol, vitriolic minerals, however impure, were employed in making ink, dye-liquors, and other things. Places for boiling vitriol were not then established, and therefore Pliny beheld with wonder blue vitriol, which in his time was made only in Spain, as a thing singular in its kind, or which had not its like. On this account those salts only were known which occur in a native state, or which crystallize as it were of themselves, without any artificial preparation, as is the case with bay salt. But that neutral salt, formed of muriatic acid and ammonia, occurs very seldom in a native state, and almost exclusively among the productions of volcanoes. I do not, however, suppose that this volcanic sal-ammoniac was the first known, but that it was first considered to be sal-ammoniac after that salt had been long obtained by another method, and long used. But even if it should be believed that our sal-ammoniac was known to the ancients, how are we to discover it with certainty in their writings? This salt has little or nothing by which these writers could characterize it. Neither its external form nor taste is so striking that it could be described by them with sufficient precision. The use of it also could not at that time be so important and necessary, as to enable us to determine whether they were acquainted with it; whereas, on the other hand, green vitriol and alum can easily be distinguished among the materials for dyeing. Nay, if this salt had been then made, as it is made at present in Egypt, and if any allusion to it were found, one might readily conjecture that sal-ammoniac were really meant. But even though it must be admitted that traces of sublimation being employed occur in the writings of Dioscorides and others, who lived nearly at the same period, we are not authorized to suppose that the knowledge of it was sufficient for the preparation of this salt. Besides, there are two properties with which the ancients might have accidentally become acquainted, and which in that case would have been sufficient to make known or define to us this salt. In the first place, by an accidental mixture of quick-lime, the strong smell or unsupportable vapour diffused by the volatile alkali separated from the acid might have been observed. In the second place, it is very possible that the complete volatilization of this salt on burning coals may have been remarked; for it had been long known that common salt decrepitates in the fire. This excited wonder, and in examining other salts people were accustomed to observe whether they possessed that property also. Had any one, with this view, thrown a bit of sal-ammoniac on a burning coal, he must have seen with astonishment that instead of decrepitating it became entirely volatilized. For this experiment, however, very pure sal-ammoniac would have been necessary. Had a little common salt been mixed with it, decrepitation would not have been altogether prevented; and if the sal-ammoniac had been rendered impure by earthy particles, as is almost always the case with the volcanic, some earth at least would have remained behind on the coals. The name sal-ammoniacus is indeed old; but as those who, in consequence of the name, considered the alumen of the ancients to be our alum, and their nitrum to be our saltpetre, were in an error, we should be equally so were we to consider their sal-ammoniac to be the same as ours. Our forefathers believed that the ancient writers were acquainted with all minerals, as well as with all plants; and when they discovered a new one, they searched in old books till they found a name which would suit it, or which at any rate had not been given to another. Our sal-ammoniac, in all probability, acquired in the same manner its name, which is not often to be found in the writings of the ancients 1. When everything they have said of it is collected and impartially examined, no proofs will be found that under that name they understood our sal-ammoniac. On the contrary, one will soon be convinced that sal-ammoniacus was nothing else than impure marine salt. As the ancients were not acquainted with the art of separating salts, of refining and crystallising them, they gave to each variety or kind in the least different, which was distinguished either by the intermixture of some foreign substance or by an accidental formation, a particular name; and, considering the wants of that period, this method was not so bad. For among the impure saline substances, there were always some which were found to be fitter than others for certain purposes. On this account they distinguished with so much care misy, sory, chalcitis and melanteria, instead of which we use a substance contained in all these minerals, that is to say, green vitriol. Our apothecary shops however have at present the lixivious salt under the name of various plants, from which it is extracted, with different degrees of purity. When this is known, it will excite no wonder that the salammoniacus of the ancients was nothing else than our com 1 It is indeed a matter of indifference whether the name be derived from appos, arena, or rather from Ammonia, the name of a district in Libya, where the oracle of Jupiter Ammon was situated. The district had its name from sand. An H also may be prefixed to the word. See Vossii Etymol. p. 24. But sal-armoniacus, armeniacus, sal-armoniac, is improper. mon salt. Dioscorides and Pliny speak of it expressly as a kind of this salt; and Columella1, in a prescription for an eye-salve, recommends rock-salt, either Spanish, Ammonia cal, or Cappadocian. Pliny says that sal-ammoniacus was found in the dry sandy deserts of Africa, as far as the oracle of Ammon. It is stated, both by him and Dioscorides3, that this salt can be split or broken into smooth pieces; and the former adds, that the best are white and transparent; that it however has an unpleasant taste, but can be used in medicine. In like manner later physicians, when they wish to prescribe common salt, recommend in particular the ammoniac. Thus Aetius, who lived in the fifth century, remarks, that when fossil, or as we say at present native salt, is employed, ammoniac or Cappadocian ought to be chosen. From what is said by Pliny, it may with certainty be con-. cluded that this salt was dug up from pits or mines in Africa; for he relates, that it appeared wonderful that a piece of it, which in the pit was very light, became, on exposure to the open air, much heavier. Without repeating the explanation which he gives of this phænomenon, I shall only remark, that many kinds of rock-salt, taken from the mines of Wieliczka, experience the same change in the air; so that blocks which a labourer can easily carry in the mine, can scarcely be lifted by him after they have been some time exposed to the air. The cause here is undoubtedly the same as that which makes many kinds of artificial salt to become moist and to acquire more weight. In this case it is owing to some impurity, such as muriate of lime, which is called sal-ammoniacus fixus1, and which attracts from the atmosphere so much moisture, that it deliquesces in it to the so-called oil of lime. Synesius, who was born in Egypt in the fifth century, in the Pentapolitan town Cyrene, and who resided as bishop in Ptolemais, the capital of the district, says, in a letter wherein he describes many rarities of his native country, that what was called sal-ammoniacus 5, both according to its appearance and taste, was a salt of a good quality, fit for use; that it lay under a soft kind of stone which covered it like a crust, 2 Lib. xxxi. cap. 7, sect. 39. This name was first used by Js. Holland. 1 De Re Rust. vi. 17, 7. Lib. v. cap. |