CASTING THE ALLOYS.

The following general statements are based upon these tables:

We see that the peoples named forged their weapons and tools from very different alloys; pure copper at one extreme, bronze with 20 per cent. tin at the other. Experience had everywhere taught them that copper and bronzes poor in tin are too soft, while bronzes with an excess of tin could not be used for weapons and tools on account of being too brittle.

They had also learned that lead and zinc considerably lessened the strength and tenacity of weapon bronze, while small quantities of iron, nickel, and cobalt are, at least, not injurious. So all races, although we can prove that they tried very different mixtures, finally adopted very simple and tolerably constant alloys. The bronze weapons of all countries frequently contain from 6 to 16 per cent. of tin, but usually between 8 and 12, with slight contamination of iron and nickel. Few nations have allowed lead to be used, fewer yet some zinc.

For casting, the oldest races used the same kind of bronze as for weapons and tools. In many cases a few per cent. of lead were added to make the casting easier. The Romans used zinc in addition to lead in large quantity as a constituent of their alloys, and they made old bronze, bronze-brass, and brass. Afterward many nations of middle Europe used zinc alloys.

Small quantities of iron, nickel, and cobalt are found for well known reasons in nearly all bronzes as harmless impurities.

Traces ofsulphurare also found in them. This injures the quality of the alloy, and discloses the fact that such bronzes were not made from pure oxide ores, but from those containing sulphur pyrites. At the time when such bronzes were produced the mines had probably reached a considerable depth.

Some of the weapon bronzes made by the ancients contain traces ofphosphorus, an element as important in hard bronze as carbon is in steel.

The Semito-Hamitic races made excellent castings at a very early date. The Phœnicians may be mentioned as particularly skillful. It is reported that there were two immense bronze pillars that stood before the temple of Gades in the 11th century before Christ. The Tyrian founders also made a pillar for Solomon's Temple, and a metallic basin 10 ells in diameter and 5 deep. Similar large basins have been dug up in Assyria.

The art of casting statues is no less ancient. Small statuettes were cast solid; larger ones consisted of several pieces which were riveted together. In the later Grecian and old Roman days the art reached a high stage of perfection. Many cities had thousands of bronzes; gigantic pieces were constructed. The Colossus of Rhodes was 30 meters high and stood with outstretched legs astride the entrance to the smaller harbor. Ships could pass through it with sails extended. A statue of Jupiter in Tarent was 20 meters high, and one of Nero was erected in Pliny's time, 30 meters high, costing a million dollars.18

These facts give us a good idea of the technical ability of the old founders of bronze.

Analyses of antique bronzes give us some idea of their art of mixing and coloring. We presume that they soon abandoned the use of copper and pure bronze; the former yields porous casts and of a poor color; the latter material was, in later times, too costly. Lead was probably used at first for its fusibility only, but afterward it was certainly introduced for economical reasons. This cheap material was often added in very considerable quantity until they learned that leaden bronzes did not have a fine color either while fresh and clean, or when old and covered with patina.

We have also seen that zinc, as well as lead, was often added. As the color of zinc alloys was red to light golden yellow (red metal, brass), they tried to dispense with tin entirely, as its price was higher than that of zinc (cadmia, as it was called). But they soon became convinced that for fine statues, at least, a small quantity oftin was a necessity. Generally a zinc-brass was used for statues.

To prevent the metallic constituents from separating during fusion, the mass was kept thick and pasty by putting in old scrap bronze that had been often melted and contained oxides. The smelters also knew that the metals, particularly the tin, grew smaller every time it was melted, in consequence of oxidation, slagging, and evaporation.19The Romans therefore added, besides the scrap bronze, an eighth part of "silver lead,"i. e., a mixture of tin and lead.

Finally, in regard to the color of the castings, the ancients collected valuable experiences. Cadmia (zinc ore) was used to impart a golden color to the bronze.20Alloys rich in tin were used for mirrors, and arsenic was employed to make them white.21

The moulds originally employed were very primitive. For simple objects a corresponding hole was dug in the sand or clay soil. Complicated figures had to be formed in clay, and the metal was cast in the clay mould. If the mould was to serve for several castings, it had to be made of baked clay, stone, brick, or other durable material. Organic substances were mixed with the clay to prevent uneven shrinkage and cracking.

Hollow casting is more difficult; first a core is formed corresponding to the hollow in the figure; over this the figure is formed, and over that the mantle,i. e., the negative, or mould. The latter is taken off, the figure taken away from the core, the mantle replaced, and the metal poured into the space between the core and the mantle. In this case it is difficult to take off the mantle so clean and put it back so accurately that the parts will not be disturbed. To avoid this difficulty a wax model may be built on the core, and the mantle formed over this, and then when the mould is dry it can be heated and the wax melted out.

The Phœnicians and Egyptians must have used one or the other of these devices for their hollow castings.

The Greeks appear at first as pupils and imitators of the Phœnicians, but they soon surpassed their teachers in forms as well as skill. They knew how to make their moulds so perfect, and were able to place their cores so near the mantles, that the castings were as thin as cardboard. The master founders of to-day have not reached that perfection.

We have already seen that only very pure bronze is suitable for weapons and tools. It must be well "cooked," and all sulphur, lead, and tin must be completely removed by oxidation. The best results are obtained with from 8 to 12 per cent. of tin. A bronze having this composition is tenacious and has a hardness of at least 4.

But the ancients were able to make much harder wrought bronzes, as proved by our collections of weapons and tools.

Unfortunately we have no record of the devices employed; but as we are able to make just such products and with simple means, we may assume that the ancients employed essentially the same methods. In our experience the following conditions are essential for the manufacture of hard bronze:

1. A particular treatment.

2. A small amount of phosphorus.

It is well known that normal weapon bronze, unlike iron, is softened by rapid cooling, but is hardened by hammering and rendered more compact.22

By repeating this process, the bronze gains in hardness and strength, and sheet bronze becomes lamellar by hammering or rolling, and hence acquires a certain elasticity.23Besides, a slight admixture of iron or nickel seems advantageous, but a slight amount ofphosphorusis of the highest importance. The latter point may be somewhat enlarged on.

Ordinary bronze always containsoxidesof copper and tin, the quantity increasing with the number of times it is recast. This oxide makes it pasty, so that the different constituents do not separate, and the casting is homogeneous.24This admixture of oxide does no harm for castings in which strength is not demanded; but is of importance for weapon bronze; the strength of which is considerably diminished by the presence of the oxide.

In this respect a slight amount of phosphorus is an advantage by preventing the formation of oxides, and consequently the mixture remains a thin fluid until it begins to solidify. On the other hand the metals are liable to separate. This evil can be avoided if the alloy is allowed to cool nearly to solidificationbefore casting, and then cooled rapidly. Under these circumstances a homogeneous alloy is obtained that is nearly fifty per cent. stronger and about 200 per cent. more tenacious than bronze that contains oxides. The hardness and strength can be still further increased by chilling and hammering.

Besides the indirect influence of phosphorus, it also has thedirecteffect of hardening the bronze, because the compounds of phosphorus with copper and tin have a very considerable hardness. These facts, as well as the circumstance that we possess antique bronzes of extraordinary hardness, induced me, with the consent of Baron Sacken, to test the hardness of the bronze weapons in the Vienna Cabinet of Antiquities. Some hard pieces,25were sent to Prof. Ludwig, who followed the question with interest and agreed on the method of making the analyses. The results were satisfactory. The bronzes contained traces and up to one-fourth per cent. of phosphorus. Its presence had prevented the formation of oxides in these bronzes, and consequentlythe weapons were of extraordinary hardness. It now remains to ascertain how the ancients made these phosphorus-bronzes. It is evident that the phosphorus was not put directly into the metal, as is generally done at present. There is another method so simple that we can assume that the ancients employed it unintentionally. I refer to smelting the copper or bronze with charcoal and any salt of phosphorus. In this case the carbon would liberate phosphorus from the phosphoric acid, and it would be taken up by the melted metal.

The ancient metallurgists may have made use of the eruptive rocks that contain apatite, and with which copper ores are so often associated, for slag or flux, or the phosphates that occur in the gangue may have been smelted along with the ores; in both cases some phosphorus would get into the metal. Finally it is not impossible that the ancients did not put in phosphorus salts in some form. First of all I would mention certain vegetable and animal substances that are rich in phosphorus, especiallyblood,26which was a favorite with the old metallurgists and alchemists as having a powerful enchantment. In each of the cases referred to some phosphorus got into the metal, which thus acquired a considerable hardness that could be increased in the well known manner by chilling and hammering. Under certain circumstances weapons and tools were made almost as hard as steel.

We can easily comprehend how bronze with these excellent qualities could compete with steel at a time when rich ores were still abundant, and thus it checked and restrained the development of the iron industry.

Egypt.—The wrought metal of the Egyptians is a pure bronze with 6 to 14 per cent. of tin; 22 per cent. is an exceptional case; 1 per cent. of iron is not rare.

The Egyptian cast metal is a plumbiferous bronze, with 4 to 11 per cent. tin, and 7 to 12 of lead; in one case 16 per cent. tin; rarely 2 or 3 per cent. of zinc.

Assyria.—The Assyrian bronze is very pure. It consists of copper, 10 to 14 per cent. of tin, and traces of iron and nickel; in one case 18 per cent. of tin.

Greece.—Their wrought bronze for tools and weapons contains 10 to 12 per cent. of tin and traces of nickel and cobalt; in one case 18 per cent. of tin.

The cast bronze has in part the same composition as wrought bronze. (Statues were rarely cast from pure copper.) A small quantity of lead was sometimes added, especially in later times, for statues and coin. The later coins contained 5 to 7 per cent. lead, even 20 per cent. in exceptional cases. Macedonian coins were of quite pure bronze.

Italy.—Roman weapons (found at Hallstadt) contain 11 to 16 per cent. of tin, in some cases some zinc or lead, also nickel and iron as impurities. Roman hatchets found in Gaul contain 20 or 25 per cent. of tin. We have too few analyses to give us a correct view of the matter, but on the contrary we have numerous analyses of Roman castings.

Ornamental Roman bronze for flexible articles contains less tin and lead. For less flexible objects bronze-brass with 1 to 7 per cent. of tin, and 5 to 12 per cent. of zinc, was employed; and for brittle but brilliant objects, like buckles and mountings, an almost pure brass was used, with 15 to 24 per cent. of zinc and little or no tin. Lead is found in all these alloys in small quantities, rarely more than 1 per cent.

The statues contain from 6 to 10 per cent. of tin, 0 to 3 per cent. zinc (in one case 14), and frequently from 10 to 12 per cent. of lead (once even 20), so that Roman statue bronze may be called lead-bronze with zinc in it.

Coin metal varied its composition at different times. In the days of the Republic a lead-bronze rich in tin (5 to 12 per cent.) was used. Under the early emperors brass or impure copper came into use. After the time of Marcus Aurelius an improvement is noticeable; the metal then in use can be called stanniferous brass (1 to 4 of tin). Under the Byzantines, coins were again struck from impure copper.

These are the most important alloys of the Romans. In general we may say that the zinc alloys held an important place among the Romans.

Gaul.—For weapons they employed a very pure bronze with 2 to 15 per cent. of tin. Traces of nickel were rare. Cast bronze contained a few per cent. of lead.

Britain.—The weapon bronze contained from 7 to 14 per cent. of tin. Cutting weapons not infrequently contain 1 to 3 per cent. of lead, and traces of iron. Ornament bronze does not differ from weapon bronze. Traces of sulphur are not rare, which points to the use of pyritical ores.

Alps.—Swiss weapon bronze contains 8 to 13 per cent. of tin (in one case even 16 per cent.), not infrequently 1 per cent. of lead and traces of silver, very often ½ to 1 per cent. of nickel and traces of iron (once as much as 3 per cent. of iron). The Swiss ornamental bronze has the same composition.

Bavaria.—Wrought bronze contains 8 to 12 per cent. of tin (in tools 17 and even 25 per cent.), and often as much as 1 per cent. of lead, traces of nickel and cobalt. Ornamental bronze has the same composition. A few per cent. of zinc is also found.

Bohemia.—The wrought metal contains 5 to 11 per cent. of tin and traces of iron and sulphur, from which we conclude that their ores contained pyrites. Their cast metal also contains lead.

North Germany.—The wrought metal contains 8 to 16 per cent. of tin, with frequently 1 per cent. of nickel. A sword contained only 5 per cent. of nickel, an ax 24 per cent. These are exceptions. The ornament bronzes contain also a few per cent. of lead; exceptionally, a considerable quantity of zinc. The ornamental metal in the Rhine region, Nassau, and Hesse contains 5 to 15 per cent. of zinc with the same of tin. At one time a rich bronze is used, at another quite pure brass, and then a bronze-like brass.

Denmark.—The Danes employed the same metal for weapons that they did for ornaments. It contained 5 to 12 per cent. of tin, and most of it 1 per cent. of zinc, but never lead; in one case only 2 per cent. of tin. Nickel and cobalt often occur, ½ per cent. of each; iron in traces.

Russia.—The Russian weapon bronze contains from 9 to 16 per cent. of tin, and traces of nickel. Arrows contain a little lead, up to 5 per cent. Ornament bronze frequently contains in addition a few per cent. of zinc.

The ornamental bronze of the Baltic provinces is a brass containing 15 to 20 per cent. of zinc, 3 to 4 per cent. of lead, and 1 to 2 per cent. of tin.

In Russia, as in other countries, the brass alloys belong to a later epoch; in older times real bronze was chiefly used for ornaments as well as other purposes.—Translated from advanced sheets furnished by the author.

We have previously spoken of the largeSequoiæof California, which have justly a universal celebrity, and shall now render our remarks upon the subject completer.

If there is any sight that can throw us into mute contemplation and show us the littleness of our own nature, it is assuredly that of high mountains like Mont Blanc, or waterfalls like Niagara. But yet we do not at the first instant take in all the grandeur of these, but must make the tour of Mont Blanc, or pass under the falls of Niagara and study it at different points in order to obtain a just idea of such marvels. And so it is with regard to the vegetable curiosities of the Sierra Nevada, in California.

When points for comparison fail us, our eye, one of the most imperfect of instruments, never gives us an accurate idea of objects, and it is for this reason that we have placed upon the annexed figure a five-story Paris house, drawn to the same scale as the "Grizzly Giant," one of the most ancientSequoiæof the Mariposa Grove, in California. This true vegetable giant is 105 feet in diameter at the base, and 69 feet at 13 feet from the ground. It has, like many of theSequoiæthat surround it, been struck by lightning, but, in spite of that, its total height is still more than 300 feet. Some of its branches are more than six feet in diameter. Those who have seen our old oaks in the forest of Fontainebleau will be able to compare the effect of time and lightning upon such venerable relics, these in California being possibly contemporaries of the Roman Empire. A few of the trees have been razed to the base, and serve as floors for dancing halls, while others, that have fallen, have been cut lengthwise and serve as bowling alleys. What especially distinguishes the wonderful region in which theseSequoiægrow is the cleanness and beauty of the plains upon which they are found. In the virgin forests of South America, under the influence of a warm and damp atmosphere, the vegetation is so rank that, in order to open a passage, one is obliged to use an ax on the vines and thickets of interlaced plants. In California, on the contrary, theSequoiæ, which are situated at an altitude of from 5,000 to 7,000 feet above the Pacific Ocean, are easily accessible. The routes are almost traced by nature, dangerous animals are rare, the summer temperature is delicious there, and hotels are everywhere being erected, as in Switzerland, to serve as a retreat and promenading place for tourists.—La Nature.

THE "GRIZZLY GIANT," ONE OF THE CALIFORNIAN SEQUOIÆ.

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FOOTNOTES:1Royal Institution of Great Britain.2Comptes Rendusof the French Academy of Sciences.3It is often desirable to make one of the apertures twice the diameter of the rest; it causes a greater intensity to be given to one image, and that facilitates the calculation of time, while it furnishes points for the comparison of the movements of the lower limbs with those of the arms.4Ang. Guerout, inLa Lumiere Electrique.5Abbe Moigno, in his treatise on telegraphy, assigns the date of 1838 to this publication; but Mr. Zetsche (d.c.) gives it as 1811. We shall consider the latter as the true date; for, in 1838, there was no reason for publishing Soemmering's memoir, and especially for proposing improvements in his apparatus.6Abstract of a paper read before the New York Academy of Sciences.7Trans. Am. Med. Ass'n, 1880.8In fœtal syphilis it is assumed that the spermatozoa may be the carriers of the disease; but no microscropist has yet described a separate species of spermatozoon for such cases.9"The Philosophy of Mystery," London, 1841; cited by Hammond in his work on "Insanity."10See articles by Dr. Hammond in this journal for 1865 and in the "Journal of Psychological Medicine" for 1869, also his "Sleep and its Derangements," Philadelphia, 1872, and his "Treatise on Insanity," New York, 1883.11Yung, "Le sommeil normal et pathologique," Paris, 1883.12"Leçons sur l'appareil vaso-moteur," t. ii., p. 154.13"Principles of Psychology," vol. i., pp. 88, 89.14"Les causes du sommeil," "Revue scientifique," t. xix.15Yung,op. cit.16Magnetic iron and pyrites in basic rocks; tin stone in granite and porphyry.17Ancient authors report cases of this kind.18The largest bronze statue of modern times is the "Bavaria" in Munich, which is 20 meters high and weighs 80 tons. It consists of 12 pieces and cost about a quarter of a million dollars.19When a bronze is remelted six times the percentage of tin is reduced to half the original (Dumas). The evaporation of the metal can be shown by holding a cold plate on it while melted. Tin is immediately deposited on it.20They usually made a copper and zinc alloy, but it is possible that they also understood the art of embedding the casting in zinc ore (calamine) and heating strongly, whereby the surface of the metal was "cemented" and colored.21On examining a broken surface of an antique mirror, it will be seen that only the outside is white. It is probable that the finished mirror was embedded in some arsenical substance and heated, which cemented and colored the surface.22Uchatius makes his famous hard bronze by cooling and hydraulic pressure. Bronzes with 8 to 12 per cent. of tin are most benefited by this process. Bronzes with very little tin in them are but little affected by chilling and hammering (Riche). Alloys that are hard already, such as bronzes rich in tin and phosphorus, become too brittle and useless by repeated hammering.23When a cast sheet of inelastic bronze or brass is hammered or rolled, it "feathers."24The Romans preferred to put in some bronze that had been repeatedly cast.25One piece was scarcely scratched by feldspar, another by quartz. The Greek and Roman weapons in the Berlin Museum were tested as to hardness by Dr. Von Dechend at the suggestion of the Director-General, Von Schone. All of them were scratched by fluorspar; there were no hard bronzes among them. If the races ofclassicalantiquity were not acquainted with hard bronze, it is easy to see why they soon began to use iron, in contrast with the Semitic-Hamitic races.26Excrements were also much used by the alchemists and pharmacists of the middle ages.

1Royal Institution of Great Britain.

2Comptes Rendusof the French Academy of Sciences.

3It is often desirable to make one of the apertures twice the diameter of the rest; it causes a greater intensity to be given to one image, and that facilitates the calculation of time, while it furnishes points for the comparison of the movements of the lower limbs with those of the arms.

4Ang. Guerout, inLa Lumiere Electrique.

5Abbe Moigno, in his treatise on telegraphy, assigns the date of 1838 to this publication; but Mr. Zetsche (d.c.) gives it as 1811. We shall consider the latter as the true date; for, in 1838, there was no reason for publishing Soemmering's memoir, and especially for proposing improvements in his apparatus.

6Abstract of a paper read before the New York Academy of Sciences.

7Trans. Am. Med. Ass'n, 1880.

8In fœtal syphilis it is assumed that the spermatozoa may be the carriers of the disease; but no microscropist has yet described a separate species of spermatozoon for such cases.

9"The Philosophy of Mystery," London, 1841; cited by Hammond in his work on "Insanity."

10See articles by Dr. Hammond in this journal for 1865 and in the "Journal of Psychological Medicine" for 1869, also his "Sleep and its Derangements," Philadelphia, 1872, and his "Treatise on Insanity," New York, 1883.

11Yung, "Le sommeil normal et pathologique," Paris, 1883.

12"Leçons sur l'appareil vaso-moteur," t. ii., p. 154.

13"Principles of Psychology," vol. i., pp. 88, 89.

14"Les causes du sommeil," "Revue scientifique," t. xix.

15Yung,op. cit.

16Magnetic iron and pyrites in basic rocks; tin stone in granite and porphyry.

17Ancient authors report cases of this kind.

18The largest bronze statue of modern times is the "Bavaria" in Munich, which is 20 meters high and weighs 80 tons. It consists of 12 pieces and cost about a quarter of a million dollars.

19When a bronze is remelted six times the percentage of tin is reduced to half the original (Dumas). The evaporation of the metal can be shown by holding a cold plate on it while melted. Tin is immediately deposited on it.

20They usually made a copper and zinc alloy, but it is possible that they also understood the art of embedding the casting in zinc ore (calamine) and heating strongly, whereby the surface of the metal was "cemented" and colored.

21On examining a broken surface of an antique mirror, it will be seen that only the outside is white. It is probable that the finished mirror was embedded in some arsenical substance and heated, which cemented and colored the surface.

22Uchatius makes his famous hard bronze by cooling and hydraulic pressure. Bronzes with 8 to 12 per cent. of tin are most benefited by this process. Bronzes with very little tin in them are but little affected by chilling and hammering (Riche). Alloys that are hard already, such as bronzes rich in tin and phosphorus, become too brittle and useless by repeated hammering.

23When a cast sheet of inelastic bronze or brass is hammered or rolled, it "feathers."

24The Romans preferred to put in some bronze that had been repeatedly cast.

25One piece was scarcely scratched by feldspar, another by quartz. The Greek and Roman weapons in the Berlin Museum were tested as to hardness by Dr. Von Dechend at the suggestion of the Director-General, Von Schone. All of them were scratched by fluorspar; there were no hard bronzes among them. If the races ofclassicalantiquity were not acquainted with hard bronze, it is easy to see why they soon began to use iron, in contrast with the Semitic-Hamitic races.

26Excrements were also much used by the alchemists and pharmacists of the middle ages.

Transcriber's Note:Inconsistent spelling and hyphenation are as in the original.

Transcriber's Note:

Inconsistent spelling and hyphenation are as in the original.

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