Chapter V: Means of Protection and Preservation of Stone (2)

As Preyer puts it, the activity of the cerebrum is a sort of respiration, while its repose is a sort of asphyxia of this organ. It is certain that every psychical act, every thought, involves a certain consumption of oxygen by the nervous substance. During waking, this gas is furnished to the brain in the blood. If the blood supply fails, those forms of activity which we denominate consciousness, attention, volition, and thought cease. This is easily proved by compression of the carotids. It is known that in the waking hours the muscles, as well as the nerves and the nerve-centers, as a consequence of that activity, produce substances easily oxidizable, among which is lactic acid. Some have even attributed the sense of fatigue which we experience after prolonged exertion to the presence of this acid in the blood.[15] According to Preyer, after the work of the day is done, and the quiet of sleep is sought, the waste materials of which we have spoken, and which he proposes to call _ponogènes_ (substances which cause fatigue), being accumulated in the tissues, little by little undergo decomposition, by taking oxygen from the blood. They thus divert a considerable quantity of this gas from the cerebrum, the cells of which, deprived of this element so indispensable to their activity, enter into a state of relative repose. These waste matters are, then, the physical cause of sleep, which will be the more profound and prolonged the more the blood is charged with the excrementitious products of function. Preyer has experimented on animals by injecting varying quantities of lactic acid into their blood, and has produced a deep somnolent condition which could not be distinguished from natural sleep. The use of lactate of sodium in the human subject has sometimes been attended with a like hypnotic effect. Further researches are needed before the question can be considered as settled.--_N. Y. Med. Jour._

* * * * *

PREPARATION OF CHLORHYDRINES.

The usual methods of preparing chlorhydrines are in part inconvenient, in part unsatisfactory in yield. A. Ladenburg therefore proposes the following process, using ethylen-chlorhydrine as an example:

Glycol is heated in a distillery apparatus to 148° C., and a _slow_ current of dry hydrochloric acid passed through it. The water formed and the glycol-chlorhydrine distill over and are collected in tubulated receivers. The temperature of the bath is gradually raised to 160° C., when all the glycol is completely decomposed, except a trifling residue. The distillate is mixed with two or three volumes of ether, and then freed from any hydrochloric acid present with potassium carbonate. The ethereal solution is drawn off, and completely dried over freshly fused potassium carbonate.--_Berl. Ber._

* * * * *

A NEW METHOD FOR THE DETECTION OF SUGAR IN THE URINE.

At a recent meeting of the Clinical Society of London, Dr. Oliver gave a demonstration of the method he employs for the detection of sugar in the urine by means of test-papers. The test-papers were charged with the carmine of indigo and carbonate of soda. When one was dropped into an ordinary half inch test tube, and as much water poured in as just covered the upper end, and heat applied, a transparent and true blue solution, resembling Fehling's in appearance, was obtained. (A transparent solution could not, at the meeting, be produced from the London water. The characteristic reaction with grape sugar was, however, unimpaired).

If with the paper one drop of diabetic urine had been added, shortly after the first simmer, a beautiful series of color changes appeared; first violet, then purple, then red, and finally straw color; while, on the other hand, one drop of non-diabetic urine induced no alteration of color. The colors returned in the inverse order on shaking the tube, which allowed the air to mingle with the liquid. Reheating restored the colors again.

Confirmation of the presence of glucose was obtained by dropping in a mercuric chloride paper, while the solution was still quite hot, after the complete development of the indigo reaction. Then there was produced immediately a blackish green precipitate. No such precipitation occurred when a drop of non-saccharine urine was under examination by the indigo test; then the blue solution was merely turned into a transparent green one.

This test, as Dr. Oliver pointed out, discovers (_a_) the normal sugar; (_b_) the varying proportions of sugar which fill in the gap between the normal amount and that which characterizes diabetes mellitus, as in liver derangements and vaso-motor disturbances; (_c_) diabetic proportions.

It possesses the following advantages over Fehling's test:

1. It will detect sugar in any proportion in the presence of albumen, peptone, blood, pus, or bile, and as readily as in ordinary diabetic urine.

2. It gives no play of colors with uric acid.

3. It possesses portability, cleanliness, and stability.

Moore's, Trommer's, and Boettger's bismuth tests are all inferior in delicacy.--_British Medical Journal._

* * * * *

CHEMICAL COMPOUNDS MADE BY COMPRESSION.

By M. W. SPRING.

The author has previously shown the possibility of uniting the fragments of solid bodies by the sole action of pressure. He also established at the same time the possibility of forming chemical compounds by means of pressure. Thus he obtained cuprous sulphide by compressing a mixture of sulphur dust and copper; mercuric iodide, by compressing mercuric chloride with potassium iodide, etc. Finally, by compressing in the same manner mixtures of the filings of different metals, he formed alloys having for equal compositions the same melting points as those obtained by fusion.

The last mentioned facts certainly establish the possibility of causing bodies to enter into chemical reaction by the mere agency of a mechanical energy. This result is closely linked with another obtained during the course of the same investigation: the polymerization of certain simple bodies, _e. g._, sulphur, by the action of pressure. The author had drawn a general conclusion from his experiments, and had announced that matter takes, below a given temperature, a state corresponding to the volume which it is compelled to occupy.

He has since undertaken a methodical study of the chemical reactions accomplished by the action of pressure. He had already shown the possibility of forming metallic arsenides by compressing mixtures of arsenic and of the filings of different metals (_Bulletin de l'Académie Royale de Belgique_, t. v., 1883), and he now communicates the results obtained by compressing mixtures of sulphur and of certain metals or non-metals. The results not merely confirm the author's former conclusions, but they throw a new light on the relations of organic and inorganic chemistry, and exhibit the so-called simple bodies as capable of assuming a peculiar constitution varying according to the conditions in which they are placed, and the actions to which they are submitted.

He used the metals in the state of fine filings immediately mixed with flowers of sulphur previously thoroughly washed. The mixtures were made in atomic proportions and were submitted to a preliminary pressure of 6,500 atmospheres. They then assumed the state of a hard compact mass, showing, on examination with the microscope, that the reaction of the sulphur and the metal had taken place wherever the elements were in contact. The mass obtained was then reduced into fine powder and compressed again from twice to eight times.

1. _Sulphur and Magnesium._--After six compressions there was obtained a gray mass with a feebly metallic surface luster. It dissolves in water at 50° to 60° with a slow escape of hydrogen sulphide, the liquid becoming of a golden yellow. A drop of hydrochloric acid occasions immediately a very strong escape of hydrogen sulphide, while free sulphur is deposited. Hence magnesium and sulphur combine under the action of pressure, forming magnesium sulphide and possibly a polysulphide.

2. _Sulphur and Zinc._--Three compressions yield a block deceptively similar to native blende with metallic luster. Dilute sulphuric acid dissolves the block slowly with an escape of hydrogen sulphide.

3. _Sulphur and Iron._--After four compressions a block is obtained which the file scarcely touches. Dilute sulphuric acid dissolves it easily with continuous escape of hydrogen sulphide. If the product of compression is heated in a closed tube no luminous phenomenon is observed, the body entering into tranquil fusion. Hence the potential heat of the free sulphur and iron has been realized during the compression.

4. _Sulphur and Cadmium._--Three compressions give a yellowish-gray homogeneous mass. The powder is yellow, but less pure than that of cadmium sulphide obtained by precipitation. Strong hydrochloric acid dissolves the mass with escape of hydrogen sulphide.

5. _Sulphur and Aluminum._--Result incomplete. After five compressions a mass is obtained which, in contact with moist air, gives off an odor of hydrogen polysulphide.

6. _Sulphur and Bismuth._--The combination takes place with great ease.

7. _Sulphur and Lead._--The combination is still more easy.

8. _Sulphur and Silver._--The action is slow; eight compressions are necessary.

9. _Sulphur and Copper._--Three compressions complete the combination. When the product of the compression is heated, there is no development of heat or light.

10. _Sulphur and Tin._--Three compressions give a block which yields a yellowish-gray powder, easily soluble in a hot solution of sodium sulphide. Stannic sulphide is therefore formed by the compression of sulphur and tin.

11. _Sulphur and Antimony._--After two compressions we obtain a gray-black mass having the color and luster of stibine. When powdered it dissolves with ease in hot hydrochloric acid, giving off hydrogen sulphide.

12. _Sulphur and Red Phosphorus; Sulphur and Carbon._--Result entirely _nil_; there is produced not the least trace of phosphorus sulphide nor of carbon sulphide.

CONCLUSIONS TO BE DRAWN FROM THESE FACTS.

The negative results just mentioned have an especial interest. It is established that red phosphorus has a higher specific gravity than white phosphorus, that of the former being 1.96, and that of the latter 1.82. The author's former researches (_Bulletins de l'Académie Royale de Belgique_, 49, p. 323, 1880) have shown that if sufficient pressure is applied to a body capable of assuming several allotropic states, it takes under pressure the state corresponding to its greatest density. It is consequently impossible to transform red phosphorus into white phosphorus by pressure. But we know, on the other hand, that red sulphur and red phosphorus may be mixed with impunity at common temperatures without combination ensuing; to produce combination the temperature must be raised to about 260°, the point of transformation of red phosphorus into white phosphorus.

It is thus established that red phosphorus must first be changed from its allotropic condition before entering into combination with sulphur. The pressure opposing this change renders also the act of combination impossible; red phosphorus appears to us like a body which has lost its chemical faculties.

Thus, the combination of an element with itself, _i. e._, its polymerization, has really the effect of extinguishing its energy, rendering it incapable of fulfilling certain functions. The chemistry of red phosphorus, more simple than that of white phosphorus, may be considered as the chemistry of a deadened body. The phosphorus which is found in combination with sulphur is phosphorus sulphides, and that which enters into combinations of other kinds, is certainly not phosphorus in the red state; it is even possible, if not probable, that it is not even white phosphorus, but a substance still unknown in the free state.

We arrive at a similar but more complete conclusion as to the nature of carbon. It is known that the affinity of carbon for sulphur and even for oxygen only becomes manifest at a temperature bordering upon redness. Is not this tantamount to saying that, in order to enter into combination with another body, carbon, like red phosphorus, must first change its allotropic condition? This view is supported by the following considerations: The specific heat of amorphous carbon, and, _a fortiori_, that of graphite and diamond, form exceptions to the law of Dulong and Petit; they are too small by more than one-half. They would be normal if the atomic weight of carbon were greater than it really is; in other words, free carbon were a polymer of combined carbon. Rose has found that at a temperature of about 500° the specific heat of carbon agrees with the law of Dulong and Petit. At this temperature carbon undergoes a beginning of depolymerization, _i. e._, its chemical affinities reappear, and it burns readily in oxygen. Do not these facts show a complete parallelism between the chemical history of phosphorus and that of carbon?

Crystalline carbon, and even free amorphous carbon, are without chemical activity at the ordinary temperature; but when, in consequence of a rise of temperature, they take another state, they are transformed into a new kind of carbon, constituting a fourth allotropic state, and endowed with a prodigious capacity of combination. If these conclusions are well founded, we may venture a step further and ask, if the carbon which enters into the composition, not of mere organic compounds, but of organized bodies, is not a carbon of still another allotropic state characterized by the appearance of new properties or forms of combination which find their expression in the vital phenomena.

In other words, a derivative of carbon, before forming part of a living body, must first undergo in its atoms a transformation similar to that which permits amorphous carbon to enter into the composition of organic compounds. In this order of ideas the carbon of organic chemistry would be merely a first deadened form of the carbon of biological chemistry, while free carbon is merely the defunct remains of the carbon of organic chemistry.--_Bulletin de la Société Chimique de Paris; Chem. News._

* * * * *

COPPER ALLOYS AMONG THE ANCIENTS.

By Prof. E. REYER, PH.D., of Vienna.

The earth's crust consists in part of eruptive rocks, in part of sedimentary rocks. Both of them have served from time immemorial for building purposes; but at a very early period they were the only source from which weapons and tools could be made. Subsequently metals became known, and were employed for this purpose.

Metals are rarely met with in a pure state, but generally in combination with oxygen or sulphur. If we examine the original material of which the earth was composed, and which is frequently injected through crevices in the earth's crust, and the superjacent sediment as eruptive rock, we find it to be a mixture of different substances of a complex nature. It contains silicon, aluminum, iron, calcium, magnesium, potassium, and sodium. None of these are in a free state, but are combined with oxygen. Silicon, the lighter metals, and heavy iron do not exhibit their true metallic character, having all been changed into stone-like compounds, "calcified by contact with vital air," as the old chemists expressed it.

Of the heavy metals that are of such importance to civilization I have only mentioned iron, for this alone, in its compounds, takes any considerable part in the rock formations. Other heavy metals are met with in smaller quantities in the rocks. They are scarcely taken into account by geologists who consider the earth as a whole, but it is these rare guests that are of the greatest importance to civilization.

The metals are met with as silicates in the eruptive masses; they are also found as oxides or sulphides, scattered through different eruptive rocks in small granules.[16] Besides these, the "ores," which are workable metallic compounds, are here and there concentrated in crevices or fissures, which exist in eruptive as well as in sedimentary rocks.

_Iron_ is met with as oxide in the eruptive rocks, in fissures, and finally in thick strata and deposits within the sediment; whole mountains consist of iron ore.

_Tin_ occurs as oxide (tin stone), scattered through eruptive masses rich in quartz, also in fissures.

_Copper_, combined with sulphur, is found distributed through dark eruptive rocks, poor in silica, and also in fissures in those regions.

_Gold_ and _silver_ are mixed in smaller quantities with ores of other metals.

All these are continually exposed to atmospheric agencies toward which they act very differently. The oxidized ores of iron and tin do not change their character. The sulphur compounds, at least when near the surface, are oxidized, and hand in hand with this process goes the partial reduction of certain metals to the metallic state. Gold and silver, and to a less extent copper, are subject to this change; they are unmasked and are exposed to day light, not as stones, but as brilliant, malleable metals. Finally, the heavy ores and metallic particles are loosened from the rocks by the destructive action of water, floated off, elutriated, and washed. In undisturbed mountain ranges the mineral treasures lie in masses before our eyes.

The native shining and malleable metals (gold, silver, and copper) naturally first attracted the attention of man. They may have used the separate nuggets for ornaments as they found them, or after hammering them together into plates. This was surely the first step in the use of metals. It can scarcely be supposed that this use of soft native metals contributed much to the progress of mankind, and it is highly probable that in those early times the noble metal had but little value. The shining particles, as long as the natural supply lasted, seemed like worthless tinsel. Copper, which can be made into tools and vessels, as well as soft, poor weapons, was more highly prized. Such materials were not, indeed, suitable and able to take the place of stone tools and weapons; nevertheless, this working of metals served as preparation for the more complicated work of later times. Man learned to hammer and shape metals, and he found out that the operation was much facilitated by heating the metal.

The discovery of iron meteorites may have had some value. In these the smith first became acquainted with the properties of a hard metal. But I would not attach too much importance to this. The art of working metals is not the possession of a people that have a few meteoric knives. In my opinion the metallurgical preparation of the hard metals from their ores is alone decisive on this point.

The volks' sagas frequently mention some god or hero, who discovered and taught metallurgy, yet there is scarcely any doubt that the "god," in most cases, was human ingenuity led by chance.

We have already seen that only certain metals are found native, while the hard metals under normal conditions remain in the form of oxide or mineral. They have a strong affinity for the oxygen of the air, and can only be separated and converted into metals by powerful chemical agents. There is _one_ substance which has a still more powerful attraction for oxygen than those metals. This is ignited carbon, which, in its fight with the metallic oxides, robs them of their oxygen.

Carbon has been separated from the carbonic acid of the air by the life-giving force of the sun, and vegetable life dependent upon it. But the isolated element waits impatiently for the impulse that will enable it to unite with the vital air under flame and heat. Men that know how to utilize this process of nature possess the means of resurrecting those metallic treasures which, without its powerful assistance, would remain forever hidden from their eyes. But accident, as we have said, pointed out the way.

In numerous places visited by primeval man, as hunter and fisherman, and afterward as nomad, conflagrations broke out. Not unfrequently whole forests were burned, either intentionally or not. It could not be otherwise than that the earth's surface would get red hot in such places, and if a strong wind favored it, this would suffice to open these treasures. The glowing charcoal would rob the ores of their oxygen and leave the pure metal as melted drops or cakes.[17] Copper, tin, and iron ores could have been reduced in this way; mankind not only knew the result but also the method of reducing metals.

This process took place not once merely, but thousands of times in various parts of the earth, and thus, in my opinion, metallurgy may have become known to different races of people and at different times.

A simple trench in the ground, in which a heap of glowing coals and some pieces of ore could be subjected to a strong draught of air, suffices, under favorable circumstances, for the preparation of the metal; the oldest metallurgists had scarcely any more complete means at hand for their work.

In such primitive furnaces the well known and soft metals would naturally be worked first, and afterward copper, tin, and iron would be obtained from their ores. A variety of substances that occur together in nature would be smelted together in mixtures, and different metals would naturally be mixed and a great variety of products obtained.

CHARACTERISTICS OF COPPER ALLOYS.

The oldest civilized races used bronze for a long space of time as their chief useful metal, although some neighboring races understood the metallurgy of iron. These facts, which are in glaring contradiction to the present condition of things, require some explanation.

First it must be mentioned that _iron_ frequently contains injurious contaminations, sulphur, phosphorus, etc., and that it must have been very difficult for these primitive metallurgists to remove these contaminations, and to introduce the proper quantity of carbon into the iron. We must also consider that even a good, pure steel would be a useless product unless it was worked by a skillful and experienced smith. Finally, iron is much more rapidly destroyed by oxidation than bronze. These negative considerations certainly favored the rule of bronze for a long time.

The following facts must be fixed in mind regarding the manufacture of bronze in olden times:

1. In many districts copper and tin ores are found near together (as in Cornwall), so that under these circumstances bronze could have been obtained by smelting both at once, and together.

2. In olden times only the upper horizon of copper deposits were worked in all districts. In these, as we know, the ores are mostly oxides (with native copper). Such ores are easily worked and yield largely.

3. In regard to the mixing of metals, the metallurgists everywhere must have soon learned by experience that the metal remained soft and red when too little tin was added, while too much tin made it light colored and lustrous, but, at the same time, very brittle. Hence, we find that among all peoples the alloys used for weapons contain from 6 to 16, or, more closely, 8 to 12 per cent. of tin. These mixtures have been found to do the best.

4. Bronzes, as we shall see below, by slight admixtures and certain treatment, can be made so tough and hard that they will compare with moderately hard steel.

So we see: The metal was useful, and there was an excess of rich and easily worked ores. Under such conditions, of course, the age of bronze would flourish a long time.

Zinc ores frequently occur on copper beds, and yet zinc is rarely found in quantity worth mentioning in the bronzes of the ancients. There are two reasons for this:

1. Near the surface of the earth zinc occurs as calamine (silicate of zinc), which is a gray, unattractive, earthy looking mineral, not heavy enough to be taken for a metallic ore, and would naturally be thrown away and not put in the furnace.

2. If some zinc ore did get into the furnace, part of it would be volatilized and part oxidized by subsequent smelting.

In later times, however, we find zinc ores used a good deal. We can distinguish three types of zinc alloys:

1. Copper with 10 to 20 per cent. zinc produces a red metal, red brass, which is similar to bronze that is poor in tin.

2. Copper with 20 or 30 (and even 40) per cent. of zinc, gives a yellow metal (yellow or ordinary brass), which has more of a golden color than bronze with much tin, but quite brittle.

3. Statuary metal, which is made of copper with quite a good deal of zinc and little tin (often lead) can be called brass containing tin.

All three types may be used for casting (ornaments, statues, and coin), but are not useful for tools or weapons, because they have not sufficient strength.

After discussing the natural association of ores, and the most important alloys of copper, we will turn to the analyses of antique alloys. I have found it necessary to divide them into two groups:

1. Alloys from which the weapons and tools were _forged_. These are pure and genuine bronzes. I shall designate them as malleable metals or weapon bronzes.

2. Alloys from which ornaments, vessels, statues, and coin were _cast_. Some of these contain lead, some zinc, and some are varieties of our brass. I shall designate these as cast metals or ornamental alloys. Those substances present in some quantity were evidently put in _intentionally_, and I have classed them as admixtures, while the unintentional ones in small quantities I have designated as impurities.

I.--WEAPON BRONZES.
_________________________________________________________________
| | |
Country. | Essential | Admixtures. |Impurities.
| constituents. | |
__________|___________________|______________________|___________
| | |
Egypt |Copper+ 6 to 14 tin| .. |Iron.
Assyria | " +10 to 14 " | .. | ..
Greece | " +10 to 12 " | .. |Fe. Ni. Co.
Italy | " +11 to 16 " |Lead and Tin. |Ni. Fe.
Gaul | " + 2 to 15 " | .. | ..
Britain | " + 7 to 14 " |1 to 3 per. ct. lead. |Iron
Alps | " + 8 to 12 " |Trace to 1 p. c. lead.|Fe. Ni.
Bohemia | " + 5 to 11 " | .. |Fe. S.
N. Germany| " + 8 to 16 " | .. |Nickel.
Denmark | " + 6 to 12 " |To 1 p. c. zinc. |Ni. Co.
Russia | " + 9 to 16 " |Lead |Ni.
__________|___________________|______________________|___________

II.--CAST METAL FOR ORNAMENTS.
_________________________________________________________________
| | |
Country. | Essential | Admixtures. |Impurities.
| constituents. | |
__________|___________________|______________________|___________
| | |
Egypt |Copper+ 4 to 11 tin|7 to 17 lead. |Traces
Assyria | " +10 to 14 " | .. |Pb. Fe. Ni.
Greece | " + 6 to 12 " |Lead. |Fe. Ni.
Italy | " + 1 to 7 " |Zinc, lead. |Fe. Ni.
Gaul | " + 5 to 15 " |Lead | ..
Britain | " + 5 to 15 " |2 p. c. lead. |Nickel.
Alps | " + 4 to 12 " |Zinc. |Pb. Fe. Ni.
Bohemia | " + 4 to 11 " |Lead. | ..
N. Germany| " + 6 to 17 " |Pb. rarely zn. |Ni.
Denmark | " + 5 to 12 " |1 p. c. zn. |Fe. Ni. Co.
Russia | " + 7 to 16 " |Pb. zn. |Ni.
__________|___________________|______________________|___________

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 of _sulphur_ are 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 of _phosphorus_, an element as important in hard bronze as carbon is in steel.

CASTING THE ALLOYS.

The Semito-Hamitic races made excellent castings at a very early date. The Phoenicians 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 of _tin 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.[19] The 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.[20] Alloys 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 Phoenicians 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 Phoenicians, 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.

HARD BRONZES OF THE ANCIENTS.

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.[23] Besides, a slight admixture of iron or nickel seems advantageous, but a slight amount of _phosphorus_ is of the highest importance. The latter point may be somewhat enlarged on.

Ordinary bronze always contains _oxides_ of 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.[24] This 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 solidification _before 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 the _direct_ effect 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,[25] were 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 consequently the 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, especially _blood_,[26] which 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.

SUMMARY OF ALLOYS USED BY THE ANCIENTS.

_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_.

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THE BIG TREES OF CALIFORNIA.

We have previously spoken of the large _Sequoiæ_ of 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 ancient _Sequoiæ_ of 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 the _Sequoiæ_ that 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 these _Sequoiæ_ grow 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, the _Sequoiæ_, 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._

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