Chapter IV: Part 4

I found also, that lumps of clay, or marl, of two inches, refrigerated so as to be held in the hand in 45 minutes; those of two inches and a half in 58; and those of three inches in 75, which being compared with the time of refrigeration of iron bullets of the same diameters, gives 46 to 80 for two inches, 58 to 102 for two inches and a half, and 75 to 127 for three inches, which nearly form the ratio of 9 to 5; so that for the refrigeration of clay, more than half the time is required than for iron.

It is necessary to observe, that globes of clay heated white, lost more of their weight than iron bullets, even to the ninth or tenth part of their weight: whereas marl heated in the same fire, lost scarcely any thing, although the whole surface was covered over with scales, and reduced into glass. As this appeared singular, I repeated the experiment several times, increasing the fire, and continuing it longer than for iron; and although it scarcely required a third of the time to redden marl, to what it did to redden iron, I kept them in the fire thrice as long as was requisite, to see if they would lose more, but I found very trifling diminutions; for the globe of two inches heated for eight minutes, which weighed seven ounces, two drachms, and thirty grains, before it was put in the fire, lost only forty-one grains, which does not make a hundredth part of its weight; and that of three inches, which weighed twenty-four ounces, five drachms, and thirteen grains, having been heated by the fire for eighteen minutes, that is nearly as much as iron, lost only seventy-eight grains, which does not make the hundredth and eighty-first part of its weight. These losses are so trifling, that it may be looked upon, in general, as certain that pure clay loses nothing of its weight in the fire; for those trifling diminutions were certainly occasioned by the ferruginous parts which were found in the clay, and which were in part destroyed by the fire. It is also worthy of observation, that the duration of heat in different matters exposed to the same fire for an equal time, is always in the same proportion, whether the degree of heat be greater or smaller.

I have made similar experiments on globes of marble, stone, lead, and tin, by a heat only strong enough to melt tin, and I found, that iron refrigerated in eighteen minutes, so as to be able to hold it in the hand, marble refrigerated to the same degree in twelve minutes, stone in eleven, lead in nine, and tin in eight. It is not, therefore, in proportion to their density, as is commonly supposed, that bodies receive and lose more or less heat, but in an inverse ratio of their solidity; that is, of their greater or lesser _non fluidity_; so that, by the same heat, less time is requisite to heat or cool the most dense fluid.

To prevent the suspicion of vainly dwelling upon assertion, I think it necessary to remark upon what foundation I build this theory; I have found that bodies which should heat in ratio of their diameters, could be only those which were perfectly permeable to heat, and would heat or cool in the same time; hence, I concluded that fluids, whose parts are only held together by a slight connection, might approach nearer to this perfect permeability than solids, whose parts have more cohesion. In consequence of this, I made experiments, by which I found, that with the same heat all fluids, however dense they might be, heat and cool more readily than any solids, however light, so that mercury, for example, heats much more readily than wood, although it be fifteen or sixteen times more dense.

This made me perceive that the progress of heat in bodies cannot, in any case, be made relatively to their density; and I have found by experience, that this progress, as well in solids as fluids, is made rather by reason of their fluidity, or in an inverse ratio of their solidity. I mean by _solidity_ the quality opposite to fluidity; and I say, that it is in an inverse ratio of this quality that the progress of heat is made in both bodies; and that they heat or cool so much the faster as they are the more fluid, and so much the slower as they are more solid, every other circumstance being equal.

To prove that solidity, taken in this sense, is perfectly independent of density, I have found, by experience, that the most or least dense matters, heat or cool more readily than other more or less dense matters, for example, gold or lead, which are much more dense than iron and copper, heat and cool much quicker; while tin and marble, which are not so dense, heat and cool much faster than iron and copper; and there are likewise many other matters which come under the same description; so that density is in no manner relative to the scale of the progress of heat in solid bodies.

It is likewise the same in fluids, for I have observed, that quicksilver, which is thirteen or fourteen times more dense than water, nevertheless heats and cools in less time than water; and spirit of wine, which is less dense than water, heats and cools much quicker; so that generally the progress of heat in bodies, as well with regard to the ingress as egress, has no affinity with their density, and is principally made in the ratio of their fluidity, by extending the fluidity to a solid; from hence I concluded, that we should know the real degree of fluidity in bodies, by heating them to the same heat; for their fluidity would be in a like ratio as that of the time during which they would receive and lose this heat; and that it would be the same with solid bodies. They will be so much the more solid, that is to say, so much the more _non fluids_, as they require more time to receive and lose this heat, and that almost generally to what I presume; for I have already tried these experiments on a great number of different matters, and from them I have made a table, which I have endeavoured to render as complete and exact as possible.

I caused several globes to be made of an inch diameter with the greatest possible precision, from the following matters, which nearly represent the Mineral kingdom.

M. Tillet, of the Academy of Sciences, made the globe of refined gold at my particular request, and the whole of them weighed as follows:

oz. d. gr.

Gold 6 2 17
Lead 3 6 28
Pure silver 3 3 22
Bismuth 3 0 3
Copper-red 2 7 56
Iron 2 5 10
Tin 2 3 48
Antimony melted, and which had
small cavities on its surface 2 1 34
Fine 2 1 2
Em 1 2 24-1/2
White marble 1 0 25
Pure clay 0 7 24
Marble common of Montbard 0 7 20
White gypsum, improperly called
Alabaster 0 6 36
Calcareous white stone of the quarry
of Anieres, near Dijon 6 6 6
Rock chrystal: it was a little too
small, and had many defects. I
presume that without them it
would have weighed 0 6 22
Common glass 0 6 21
Pure earth, very dry 0 6 16
Oker 0 5 9
Porcelain of the Court de Lauraguais 0 5 2-1/2
White chalk 0 4 49
Cherrywood, which although lighter
than most other woods, is that
which takes in the least fire 0 1 59

I must here observe, that a positive conclusion must not be made of the exact specific weight of each matter from the preceding table, for notwithstanding the precaution that was taken to render the globes equal, yet, as I was obliged to employ different workmen, some were too large, and others too small. Those which were more than an inch diameter were diminished, but those of rock chrystal, glass and porcelain, which were rather too small, we suffered to remain, and only rejected those of agate, jasper, and porphyry, which were sensibly so. This precision in size was however not absolutely necessary, for it could very little alter the result of my experiments.

Previously to ordering these globes, I exposed to a like degree of fire, a square mass of iron, and another of lead of two inches diameter, and found, by reiterated essays, that lead heated and cooled in much less time than iron. I made the same experiment on red copper, and that required more time to heat and cool than lead, and less than iron. So that of these three matters, iron appeared the least accessible to heat, and, at the same time, that which retained it the longest. From which I learn that the law of the progress of heat in bodies was not proportionable to their density, since lead, which is more dense than iron or copper, nevertheless heats and cools in less time than either. As this object appeared important, I was induced to have these globes made, and to be more perfectly satisfied of the progress of heat in a great number of different matters, I always placed the globes at an inch distance from each other, before the same fire, or in the same oven, 2, 3, 4, or 5, together with a globe of tin in the midst of them. In most of my experiments I suffered them to be exposed to the same active fire till the globe of tin began to melt, and at that instant they were all removed, and placed on a table in small cases. I suffered them to cool without moving, often trying whether I could touch them, and the moment they left off burning, and I could hold them in my hands half a second, I marked the time which had passed since I drew them from the fire. I afterwards suffered them to cool to the actual temperature, of which I endeavoured to judge by means of touching other small globes of the same matters that had not been heated. Of all the matters which I put to the trial, there was only sulphur which melted in a less degree of heat than tin, and notwithstanding its disagreeable smell I should have taken it for a term of comparison, but being a brittle matter which diminishes by friction, I preferred tin, although it required nearly double the heat to melt.

Having heated together bullets of iron, copper, lead, tin, gres, and Montbard marble, they cooled in the following order:

_So as to be held in the hand _To actual temperature._
for half a second._
Min. Min.
Tin in 6-1/2 In 16
Lead in 8 In 17
Gres in 9 In 19
Common marble in 10 In 21
Copper in 11-1/2 In 30
Iron in 13 In 38

By a second experiment with a fiercer fire, sufficient to melt the tin bullet, the five others cooled.

_So as to be held in the hand._ _To actual temperature._
Min. Min.
Lead in 10-1/2 In 42
Gres in 12-1/2 In 46
Common marble 13-1/2 In 50
Copper 19-1/2 In 51
Iron 23-1/2 In 54

By a third experiment, with a less degree of fire than the preceding, the same bullets with a fresh tin bullet, cooled in the following manner.

_So as to be held in the hand._ _To actual temperature._
Min. Min.
Tin in 7-1/2 In 25
Lead in 9-1/2 In 25
Gres in 10-1/2 In 37
Common marble 12 In 39
Copper 14 In 44
Iron 17 In 50

From these experiments, which I made with as much precision as possible, we may conclude, first, that the time of refrigeration of iron, so as to be held in the hand, is to that of copper : : 53-1/2 : 45, and so to the point of temperature : : 142 : 125.

2dly, That the time of refrigeration of iron, so as to be held in the hand, is to that of the first refrigeration of common marble : : 53-1/2 : 35-1/2 and their entire refrigeration : : 142 : 110.

3dly, that the time of refrigeration of iron, to that of gres, so as to be held in the hand, is : : 53-1/2 : 32 and : : 142 : 102-1/2, for their entire refrigeration.

4thly, That the time of refrigeration of iron to that of lead, so as to be held in the hand, is : : 53-1/2 : 27 and 142 : 94-1/2 for their entire refrigeration.

In an oven hot enough to melt tin, although all the coals and cinders were drawn out, I placed, on a piece of iron wire, five bullets, distant from one another about nine lines, after which the oven was shut, and having drawn them out, in about 18 minutes they cooled,

_So as to be held in the hand._ _To actual temperature._
Min. Min.
Melted tin in 8 In 24
Silver in 14 In 40
Gold in 15 In 46
Copper in 16-1/2 In 50
Iron in 18 In 56

In the same oven, but with a slower heat, the same bullets with an other bullet of tin, cooled,

_So as to be held in the hand._ _To actual temperature._
Min. Min.
Tin in 7 In 20
Silver in 11 In 56
Gold in 12-1/2 In 40
Copper in 14 In 43
Iron in 16-1/2 In 47

In the same oven, but with a still less degree of heat, the same bullets cooled,

_So as to be held in the hand._ _To actual temperature._
Min. Min.
Tin in 6 In 17
Silver in 9 In 26
Gold in 9-1/2 In 28
Copper in 10 In 31
Iron in 11 In 35

Having placed in the same oven five other bullets, placed the same and separated from each other, their refrigeration was in the following proportions.

_So as to be held in the hand._ _To actual temperature._
Min. Min.
Antimony in 6-1/2 In 25
Bismuth in 7 In 26
Lead in 8 In 27
Zinc in 10-1/2 In 30
Emery in 11-1/2 In 38

In the same oven, and in the same manner, another bullet of Bismuth was placed, with six other bullets, which cooled,

_So as to be held in the hand._ _To actual temperature._
Min. Min.
Antimony in 6 In 23
Bismuth in 6 In 25
Bismuth in 6 In 25
Lead in 7-1/2 In 28
Silver in 9-1/2 In 30
Zinc in 10-1/2 In 32
Gold in 11-1/2 In 34
Emery in 13-1/2 In 39

There was put in the same oven a bullet of glass, another of tin, one of copper, and one of iron, and they cooled,

_So as to be held in the hand._ _To actual temperature._
Min. Min.
Tin in 8 In 27
Glass in 8-1/2 In 22
Copper in 14 In 42
Iron in 16 In 50

Bullets of gold, glass, porcelain, gypsum, and gres, were heated together, and cooled,

_So as to be held in the hand._ _To actual temperature._
Min. Min.
Gypsum in 8 In 24
Porcelain in 8-1/2 In 25
Glass in 2 In 26
Gres in 10 In 32
Gold in 14-1/2 In 45

Bullets of silver, common marble, hard stone, white marble, and soft calcareous stone of Anieres, near Dijon, were heated like the former, and cooled,

_So as to be held in the hand._ _To actual temperature._
Min. Min.
Soft calcareous
stone in 8 In 25
Hard stone in 10 In 34
Common marble in 11 In 35
White marble in 12 In 36
Silver in 13-1/2 In 40

The whole of these experiments were made with the utmost care and attention, not only by myself but in the presence of several persons, who also endeavoured to judge of the first degree of temperature by holding the bullets for half a second in their hands, and the relations of which are more exact than those of the actual temperature, because that being variable the result must sometimes vary also.

With a view to avoid that prolixity which would necessarily attend the continual repetition in a comparative statement of the refrigeration of these different bodies, we have connected them in a general table, and taking 10,000 for the standard of comparison, their differences may be seen at one view.

A TABLE

OF THE

_Relations of different Mineral Substances._

IRON, with

First Entire
Refrig. Refrig.

Emery 10000 to 9117 -- 9020
Copper ---- to 8512 -- 8702
Gold ---- to 8160 -- 8148
Zinc ---- to 7653 -- 6020
6804
Silver ---- to 7619 -- 7423
Marble White ---- to 6774 -- 6704
Marble common ---- to 6636 -- 6746
Stone calcareous hard ---- to 6617 -- 6274
Gres ---- to 5596 -- 6926
Glass ---- to 5576 -- 5805
Lead ---- to 5143 -- 6482
Tin ---- to 4898 -- 4921
Stone calcareous soft ---- to 4194 -- 4659
Clay ---- to 4198 -- 4490
Bismuth ---- to 3580 -- 4081
Chalk ---- to 3086 -- 3878
Gum ---- to 2325 -- 2817
Wood ---- to 1890 -- 1594
Pumice-stone ---- to 1627 -- 1268

EMERY, with

Copper 10000 to 8519 -- 8148
Gold ---- to 8513 -- 8560
Zinc ---- to 8390 -- 7693
7458
Silver ---- to 7778 -- 7895
Stone calcareous hard ---- to 7304 -- 6963
Gres ---- to 6552 -- 6517
Glass ---- to 5862 -- 5506
Lead ---- to 5718 -- 6643
Zinc ---- to 5658 -- 6000
Clay ---- to 5185 -- 5185
Bismuth ---- to 4949 -- 6060
Antimony ---- to 4540 -- 5827
Oker ---- to 4259 -- 3827
Chalk ---- to 3684 -- 4105
Gypsum ---- to 2368 -- 2947
Wood ---- to 1552 -- 3146

COPPER, with

Gold 10000 to 9136 -- 9194
Zinc ---- to 8571 -- 9250
7619
Silver ---- to 8395 -- 7823
Marble common ---- to 7639 -- 8019
Gres ---- to 7333 -- 8160
Glass ---- to 6667 -- 6567
Lead ---- to 6179 -- 7367
Lead ---- to 6179 -- 7367
Tin 10000 to 5746 -- 6916
Stone calcareous tender ---- to 5168 -- 5633
Clay ---- to 5652 -- 6363
Bismuth ---- to 5686 -- 5959
Antimony ---- to 5130 -- 5808
Oker ---- to 5003 -- 4697
Chalk ---- to 4068 -- 4368

GOLD, with

Zinc 10000 to 2474 -- 9304
8422
Silver ---- to 8936 -- 8686
Marble white ---- to 8101 -- 7863
Marble common ---- to 7342 -- 7434
Stone calcareous hard ---- to 7383 -- 7516
Gres ---- to 7368 -- 7627
Glass ---- to 7103 -- 5232
Lead ---- to 6526 -- 7500
Tin ---- to 6324 -- 6051
Stone calcareous soft ---- to 6087 -- 5811
Clay ---- to 5811 -- 5077
Bismuth ---- to 5658 -- 7043
Porcelain ---- to 5526 -- 5593
Antimony ---- to 5395 -- 6348
Oker ---- to 5349 -- 4462
Chalk ---- to 4571 -- 4452
Gypsum ---- to 2989 -- 3293

ZINC, with

Silver 10000 to 8904 -- 8990
10015
Marble white ---- to 8305 -- 8424
7194
Gres ---- to 6242 -- 7333
5838
Lead ---- to 6051 -- 7947
4940
Tin ---- to 6777 -- 6240
5666
Stone calcareous soft ---- to 5536 -- 7719
4425
Clay ---- to 5484 -- 7458
4373
Bismuth ---- to 5343 -- 7547
4232
Antimony ---- to 5246 -- 6608
4135
Chalk ---- to 3729 -- 5862
2618
Gypsum ---- to 3409 -- 4261
2298

SILVER, with

Marble white 10000 to 8681 -- 9200
Marble common ---- to 7912 -- 9040
Stone calcareous hard ---- to 7436 -- 8580
Gres ---- to 7361 -- 7767
Glass ---- to 7230 -- 7212
Lead ---- to 7154 -- 9184
Tin ---- to 6176 -- 6289
Stone calcareous soft ---- to 6178 -- 6289
Clay ---- to 6034 -- 6710
Bismuth ---- to 6308 -- 8877
Porcelain ---- to 5556 -- 5242
Antimony ---- to 5692 -- 7653
Oker ---- to 5000 -- 5668
Chalk ---- to 4310 -- 5000
Gypsum ---- to 2879 -- 3366
Wood ---- to 2253 -- 1864
Pumice-stone ---- to 2059 -- 1525

WHITE MARBLE, with

Marble common 10000 to 8992 -- 9405
Stone hard ---- to 8594 -- 9130
Gres ---- to 8286 -- 8990
Lead ---- to 7604 -- 5555
Tin ---- to 7143 -- 6792
Stone calcareous soft ---- to 6792 -- 7281
Clay ---- to 6400 -- 6286
Antimony ---- to 6286 -- 6792
Oker ---- to 5400 -- 5571
Gypsum ---- to 4920 -- 5116
Wood ---- to 2200 -- 2857

COMMON MARBLE, with

Stone hard 10000 to 9483 -- 9665
Gres ---- to 8767 -- 9273
Lead ---- to 7671 -- 8590
Tin ---- to 7424 -- 6666
Stone soft ---- to 7327 -- 7959
Clay ---- to 7272 -- 7213
Antimony ---- to 6279 -- 8333
Oker ---- to 6136 -- 6393
Chalk ---- to 5581 -- 6333
Wood ---- to 2500 -- 3279

HARD CALCAREOUS STONE, with

Gres 10000 to 9268 -- 9355
Glass ---- to 8710 -- 8352
Lead ---- to 8571 -- 7931
Tin ---- to 1095 -- 7931
Stone soft ---- to 8000 -- 8095
Clay ---- to 6190 -- 6897
Oker ---- to 4762 -- 5517
Wood ---- to 2195 -- 4516

GRES, with

Glass 10000 to 9324 -- 7939
Lead ---- to 8561 -- 8950
Tin ---- to 7667 -- 7633
Stone soft ---- to 7644 -- 7193
Porcelain ---- to 7364 -- 7059
Antimony ---- to 7333 -- 6170
Gypsum ---- to 4568 -- 5000
Wood ---- to 2368 -- 4828

GLASS, with

Lead 10000 to 9318 -- 8548
Tin ---- to 9107 -- 8679
Clay ---- to 7938 -- 7643
Porcelain ---- to 7692 -- 8863
Oker ---- to 6289 -- 6500
Chalk ---- to 6104 -- 6195
Gypsum ---- to 4160 -- 6011
Wood ---- to 2647 -- 5514

LEAD, with

Tin 10000 to 8695 -- 8333
Stone soft ---- to 8437 -- 7192
Clay ---- to 7878 -- 8536
Bismuth ---- to 8698 -- 8750
Antimony ---- to 8241 -- 8201
Oker ---- to 6060 -- 7073
Chalk ---- to 5714 -- 6111
Gypsum ---- to 4736 -- 5714

TIN, with

Clay 10000 to 8823 -- 9524
Bismuth ---- to 8889 -- 9400
Antimony ---- to 8710 -- 9156
Oker ---- to 5882 -- 7619
Chalk ---- to 6394 -- 6842
Gypsum ---- to 4090 -- 4912

STONE CALCAREOUS SOFT, with

Antimony 10000 to 7742 -- 9542
Chalk ---- to 7288 -- 7312
Gypsum ---- to 4182 -- 5211

CLAY, with

Bismuth 10000 to 8870 -- 9416
Oker ---- to 8400 -- 8571
Chalk ---- to 7701 -- 8000
Gypsum ---- to 5185 -- 8055
Wood ---- to 3437 -- 4545

BISMUTH, with

Antimony 10000 to 9349 -- 9572
Oker ---- to 8846 -- 7380
Chalk ---- to 8020 -- 9500

PORCELAIN, with

Gypsum 10000 to 5301 -- 6500

ANTIMONY, with

Chalk 10000 to 8431 -- 7391
Gypsum ---- to 3833 -- 5476

OKER, with

Chalk 10000 to 8954 -- 8889
Gypsum ---- to 6364 -- 9062
Wood ---- to 4074 -- 5128

CHALK, with

Gypsum 10000 to 6667 -- 7920

GYPSUM, with

Wood 10000 to 8000 -- 5260
Pumice-stone ---- to 7099 -- 4560

WOOD, with

Pumice-stone 10000 to 8750 -- 8182

Notwithstanding the assiduity I used in my experiments, and the care I took to render the relations exact, I own there are still some imperfections in the foregoing table; but the defects are trivial, and do not much influence the general results; for example, it will easily be perceived, that the relation of zinc to lead being 10,000 to 6,051, that of zinc to tin should be less than 6,000, whereas it is found 6,777 in the table. It is the same with respect of silver to bismuth, which ought to be less than 6,308, and also with regard of lead to clay, which ought to be more than 8,000, but in the table is only 7,878. This difference proceeded from the leaden and bismuth bullets not being always the same; they melted, as well as those of tin and antimony, and, therefore, could not fail to produce variations, the greatest of which are the three I have just remarked. It was not possible for me to do better; the different bullets of lead, tin, bismuth, and antimony, which I successively made use of, were made in the same manner, but the matter of each might be somewhat different, according to the quantity of the alloy in the lead and tin, for I had pure tin only for the two first bullets; besides, there remains very often a small cavity in the melted bullet, and these little causes are sufficient to produce the little differences which may be remarked in the table.

On the whole, to draw from these experiments all the profit that can be expected, the matters which compose their object must be divided into four classes, viz. 1. Metals. 2. Semi-metals and Metallic Minerals. 3. Vitreous and Vitrescible Substances. And 4. Calcareous and Calcinable substances. Afterwards the matters of each class must be compared between themselves to discover the cause, or causes, or the order which follows the progress of heat in each, and then with each other, in order to deduce some general results.

First. The order of the six metals, according to their _density_, is tin, iron, copper, silver, lead, and gold; whereas the order in which they receive and lose their heat is tin, lead, silver, gold, copper, and iron; so that in tin alone it retains its place.

The progress and duration of heat in metals does not then follow the order of their density, except in tin, which being the least dense, is also that which soonest loses its heat; but the order of the five other metals demonstrates that it is in relation to their fusibility that they all receive and loose heat; for iron is more difficult to melt than copper, copper more than gold, gold more than silver, silver more than lead, lead more than tin; and therefore we may conclude that it is only by chance if the density and fusibility of tin be found so united as to place it in the last rank. Nevertheless, it would be advancing too much to pretend that we must attribute all to fusibility, and nothing to density. Nature never deprives herself of one of her properties in favour of another in an absolute manner; that is to say, in a mode that the first has not any influence on the second. Thus, density may be of some weight in the progress of heat; but we may safely affirm, that in the six metals it has very little comparatively with fusibility.

This fact was neither known to chemists nor naturalists; they did not even imagine that gold which is more than twice as dense as iron, nevertheless loses its heat near a third sooner. It is the same with lead, silver, and copper, which are all more dense than iron, and which, like gold, heat and cool more readily; for though the object of this, second memoir was only refrigeration, yet the experiments of the one that preceded it demonstrate, that there is ingress and egress of heat in bodies, and that those which receive it most quickly also lose it the soonest.

If we reflect on the real principles of density, and the cause of fusibility, we shall perceive, that density depends absolutely on the quantity of matter which Nature places in a given space; that the more she can make it enter therein, the more density there will be, and that gold, in this respect, is of all substances, that which contains the most matter relatively to its volume. It is for this reason that it has been hitherto thought, that more time is required to heat or cool gold than other metals; and it is natural enough to suppose, that containing double or treble the matter in the same volume, double or treble time would be required to penetrate it with heat; nay this would be true, if in every substance the constituent parts were of the same figure and ranged the same. But in the most dense the molecules of matter are, probably, of a figure sufficiently regular not to leave very void places between them; in others which are not so dense, and their figures more irregular, more vacuities are left, and in the lightest, the molecules being few, and most likely of a very irregular figure, a thousand times more void is found than plenitude; for it may be demonstrated by other experiments, that the volume of even the most dense substance contains more void space than full matter.

Now, the principal cause of fusibility is the facility which the particles of heat find in separating these molecules of full matter from each other; let the sum of the vacuities be greater or less, which causes density or lightness, it is indifferent to the separation of the molecules which constitute the plenitude; and the greater or less fusibility depends entirely on the power of coherence which retains the massive parts united, and opposes itself more or less to their separation. The dilatation of the total volume is the first degree of the action of heat; and in different metals it is made in the same order as the fusion of the mass, which is performed by a greater degree of heat or fire. Tin, which melts the most readily, is also that which dilates the quickest; and iron, which is the most difficult of all to melt, is likewise that whose dilatation is the slowest.

After these general positions, which appear clear, precise, and founded on experiments that nothing can contradict, it might be imagined that ductility would follow the order of fusibility, because the greater or less ductility seems to depend on the greater or less adhesion of the parts in each metal; nevertheless, ductility seems to have as much connection with the order of density, as with that of their fusibility. I would even affirm that it is in a ratio composed of the two others, but that would be only by estimation, and a presumption which is, perhaps not founded; for it is not so easy to exactly determine the different degrees of fusibility, as those of density; and as ductility participates of both, and varies according to circumstances, we have not as yet acquired the necessary knowledge to pronounce affirmatively on this subject, though it is most certainly of sufficient importance to merit particular researches. The same metal when cold gives very different results to what it does when hot, although treated in the same manner. Malleability is the first mark of ductility; but that gives only an imperfect idea of the point to which ductility may extend; nor can simple lead, the most malleable metal, be drawn into such fine threads as gold, or even as iron, which is the least malleable. Besides we must assist the ductility of metals with the addition of fire, without which they become brittle: even iron, although the most robust, is brittle like the rest. Thus the ductility of one metal, and the extent of continuity which it can support, depend not only on its density and fusibility, but also on the manner and space in which it is treated, and of the addition of heat or fire which is properly given to it.

II. By comparing those substances which we term _semi-metals_ and _metallic minerals_, which want ductility, we shall perceive, that the order of their density is emery, zinc, antimony and bismuth, and that in which they receive and lose heat, is antimony, bismuth, zinc, and emery; and which does not in any measure follow the order of their density, but rather that of their fusibility. Emery, which is a ferruginous mineral, although as dense again as bismuth, retains heat longer. Zinc, which is lighter than antimony or bismuth, retains heat longer than either. Antimony and bismuth, receive and keep it nearly alike. There are, therefore, semi-metals, and metallic minerals, which, like metals, receive and lose heat nearly in the same relation as their fusibility, and partake very little of their density.

But by joining the six metals, and the four semi-metals, or metallic minerals, which I have tried, we shall find the order of the densities of these ten mineral substances to be emery, zinc, antimony, tin, iron, copper, bismuth, silver, lead and gold. And that the order in which these substances heat and cool, is antimony, bismuth, tin, lead, silver, zinc, gold, copper, emery and iron, in which there are two things that do not appear to perfectly agree with the order of fusibility.

First, Antimony, which, according to Newton, should heat and cool slower than lead, since by his experiments it requires ten degrees of the same heat to fuse, of which eight are sufficient for lead; whereas by my experiments antimony is found to heat and cool quicker than lead. But it should be observed that Newton made use of the regulus of antimony, and that I employed only melted antimony in experiments. Now this regulus of antimony, or native antimony, is much more difficult to fuse than antimony which has already undergone a first fusion, therefore that does not make an exception to the rule. On the whole, I do not know what relation native antimony, or regulus of antimony, may have with the other matters I have heated and cooled; but I presume, from the experiments of Newton, that it heats and cools slower than lead.

Secondly, it is pretended, that zinc fuses more easily than silver, consequently it should be found before silver in the order indicated by experiments, if this order were in all cases relative to that of fusibility; and I own that this semi-metal seems, at the first glance, to make an exception to the law which is followed by all the others; but it must be observed, that the difference given by my experiments between zinc and silver is very trifling. The small globe of silver which I made use of was of the purest silver, without the least mixture of copper; but I had my doubts whether that of zinc were entirely free from copper, or some other metal less fusible; and therefore, after all my experiments, I returned the globe of zinc to M. Rouelle, a celebrated professor of chemistry, requesting him carefully to examine it, which having done, after several trials, he found a pretty considerable quantity of iron, or saffron of steel in it.

I have, therefore, had the satisfaction of seeing that not only my own supposition was well founded, but also that my experiments have been made with sufficient precision to evince a mixture. Thus zinc exactly follows the order of fusibility, like the other metals and semi-metals, in the progress of heat, and does not make any exception to the rule. It cannot therefore, in general, be said that the progress of heat in metals, semi-metals, and metallic minerals, is in the same ratio, or even nearly to that of their fusibility.

III. The Vitrescible and Vitreous Matters, which I tried, being ranged according to their density, are, pumice-stone, porcelain, oker, clay, glass, rock-chrystal, and gres, for I must observe, that although chrystal is not set down in the table of the weight of each matter but for six drachms 22 grains, it must be supposed one drachm heavier, because it was sensibly too small; and it was for this reason that I excluded it from the general table of relations; nevertheless, as the general result agrees with the rest, I can present the following as the order in which these different substances are cooled:

Pumice-stone, oker, porcelain, clay, glass, crystal and gres, is according to that of their density, for the oker is here before the porcelain only because, being a fusible matter, it diminished by the friction it underwent in the experiments, and, besides, their density differs so little that they may be looked upon as equal.

Thus the law of the progress of heat in vitrescible and vitreous matters is relative to the order of their density, and has little or no relation with their fusibility but by the heat required to fuse those substances being in an almost equal degree, and the particular degree of their different fusibility being so near each other that an order of distinct terms cannot be made; thus their almost equal fusibility making only one term, which is the extreme of this order, we must not be astonished that the progress of heat here follows the order of density, and that these different substances, which are all equally difficult to fuse, heat and cool more or less quick in proportion to the matter they contain.

It may be objected to me that glass fuses more easily than clay, porcelain, oker, and pumice-stone, which, nevertheless, heat and cool in less time than glass; but the objection will fail when we reflect, that to fuse glass it is requisite to have a very fierce fire, the heat of which is so remote from the degrees which glass receives in our experiments on refrigeration, that it cannot have any influence on them. Besides, by powdering clay, porcelain, and pumice-stone, and by giving them their analogous fusers, as we give to sand to convert it into glass, it is more than probable that we should fuse all the matters in the same degree of fire, and that, consequently we must look upon it as equal, or almost equal, with their resistance to fusion; and it is for this reason that the law of the progress of heat in these matters is found proportionable to the order of their density.

IV. Calcareous matters, ranged according to the order of their density, are, chalk, soft stone, hard stone, common marble, and white marble, which is the same as that of their density. The fusibility is not here of any weight, because it requires at first a very great degree of fire to calcine them; and although the calcination divides the parts, we must look upon the effect only as a first degree and not as a complete fusion. The whole power of the best burning mirrors is scarcely sufficient to perform it. I have melted and reduced into a kind of glass some of these calcareous matters; and I am convinced that these matters may, like all the rest, be reduced ulteriorly into glass, without employing for this purpose any fusing matter, and only by the force of a fire superior to that of our furnaces; consequently the common term of their fusibility is still more remote, and more extreme, than that of vitreous matters, and it is for this reason that they also follow more exactly the order of density in the progress of heat.

White gypsum, improperly called alabaster, is a matter which calcines like all other plasters by a more moderate heat than that which is necessary for the calcination of calcareous matters, and it follows the order of density in the progress of heat which it receives or loses, for although much more dense than chalk, and a little more so than white calcareous stone, it heats and cools more readily than either of those matters. This demonstrates that the more or less easy calcination and fusion produces the same effects relatively to the progress of heat. Gypsous matters do not require so much fire to calcine as calcareous, and it is for this reason that, although more dense, they heat and cool much quicker.

Thus it may be concluded, that, in general, the _progress of heat in all Mineral Substances is always nearly in a ratio of their greater or less facility to calcine, or melt_: but that when their calcination, or their fusion, are _equally difficult_, and _that they require a degree of extreme heat_, then the _progress of heat is made according to the order of their density_.

I have deposited in the Royal Cabinet the globes of gold, silver, and of all the other metallic and mineral substances which served for the preceding experiments, that if the truth of their results, and the general consequences which I have deduced, be doubted, there may be an opportunity of rendering them more authentic.

OBSERVATIONS ON THE NATURE OF PLATINA.

We have already seen, that of all the Mineral substances which I subjected to trial it was not the most dense, but the least fusible, which required the longest time to receive and lose heat. Iron and emery, which are the most difficult matters to fuse, are, at the same time, those that heat and cool the slowest. There is nothing except platina that is accessible to heat, which retains it longer than iron. This mineral, (which has not long been publicly mentioned) appears, however, to be more difficult to fuse; the fire of the best furnaces is not fierce enough to produce that effect, nor even to agglutinate the small grains, which are all angular, hard, and similar in form to the thick scale of iron, but of a yellowish colour; and although we can fuse them without any addition, and reduce them into a mass by a mirror, platina seems to require more heat than the ore and scales of iron which we easily fuse in our forge furnaces. In other respects, the density of platina being much greater than that of iron, the two quantities of density and non-fusibility unite here to render this matter the least accessible to the progress of heat. I presume, therefore, that platina would have been at the head of my table if I had put it to the experiment; but I was not able to procure a globe of it of an inch diameter, it being only found in grains[C]; and that which is in the mass is not pure, it being necessary, in order to fuse it, to mix it with other matters, which alter its nature. The Comte de Billarderie d'Angivilliers, who often attended my experiments, led me to examine this rare metallic substance, not yet sufficiently known. Chemists who have employed their time in platina, have looked upon it as a new, perfect, proper, and particular metal, different from all the rest: they have asserted, that its specific weight was nearly equal to that of gold; but that it essentially differed in other respects from gold, having neither ductility nor fusibility. I own I am of a quite contrary opinion; because a matter which has neither ductility nor fusibility, cannot rank in the number of metals, whose essential and common properties are to be ductile and fusible. Neither, after a very careful examination, did platina appear to me a new metal different from every other, but rather an alloy of iron and gold formed by Nature, in which the quantity of gold predominated over the iron; and I founded this opinion on the following facts:

[C] I have been assured, however, by a person of the first respectability, that platina is sometimes found in masses, and that he himself saw a piece that weighed twenty pounds, pure as it was extracted from the mine.

Of 8 ounces 85 grains of platina, furnished me by Comte d'Angivilliers, which I presented to a strong loadstone, there remained only 1 ounce, 1 dram, and 98 grains, all the rest was taken away by the loadstone; therefore, nearly six-sevenths of the whole was attracted by the loadstone, which is so considerable a quantity, that it is impossible to suppose that iron is not contained in the intimate substance of platina, but that it is even there in a very great quantity. I am convinced it contains much more, for if I had not been weary of these experiments, which took me up several days, I should have attracted a great part of the remainder of the 8 ounces by my loadstone, for to the last it continued to draw some grains one by one, and sometimes two. There is, therefore, much iron in platina, and it is not simply mixed with it, as with a foreign matter, but intimately united and making part of its substance; or, if this is denied, it must be supposed, that there exists a second matter in Nature which like iron may be attracted by the loadstone.

All the platina I have had an opportunity of examining, has appeared to be mixed with two different matters, the one black, and very attractable by the loadstone; the other in larger grains, of a pale yellow, and much less magnetic than the first. Between these two matters, which are the two extremes, are found all the intermediate links, whether with respect to magnetism, colour, or size of the grains. The most magnetic, which are at the same time the blackest and smallest, reduce easily into powder by a very slight friction, and leave on white paper the same marks as lead. Seven leaves of paper which were successively made use of to expose the platina to the action of the loadstone, were blackened over the whole extent occupied by it; the last left less than the first, in proportion as the grains which remained were less black and magnetic; the largest grains, which are yellow, and least magnetic, instead of crumbling into powder like the small black grains, are very hard, and resist all trituration; nevertheless, they are susceptible of extension in an agate mortar, under the reiterated strokes of a pestle of the same matter, and I flattened and extended many grains to the double or treble extent of their surface: this part of platina, therefore, has a certain degree of malleability, and ductility, whereas the black part appears to be neither malleable nor ductile. The intermediate grains participate of the qualities of the two extremes: they are brittle and hard, they break or extend under the strokes of the pestle, and afford a little powder not so black as the first.

Having collected this black powder and the most magnetic grains that the loadstone at first attracted, I discovered that the whole was iron, but in a different state from common iron. The latter reduced into powder and filings contracts moisture, and rusts very readily; in proportion as the rust increases, it becomes less magnetic, and absolutely loses this magnetical quality when entirely and intimately rusted; whereas this iron powder, or ferruginous sand found in the platina, is inaccessible to rust, how long soever it may be exposed to the air and humidity; it is also more infusible and much less dissoluble than common iron; but is, nevertheless, an iron which appears to differ only from common iron by a greater purity. This sand is, in fact, iron divested of all the combustible matter and all terrene parts which are found in common iron, and even in steel. It appears endowed and covered with a vitreous varnish which defends it from all injury. What is very remarkable, this pure iron sand does not exclusively belong to the platina ore; for I have found it, although always in small quantities, in many parts where the iron ore has been dug, and which consumed in my forges. As I submitted to several trials all the ores I had, before I used them in my experiments, I was surprised to find in some of them, which were in grains, particles of iron, somewhat rounded and shining, like the filings of iron, and perfectly resembling the ferruginous sand of the platina; they were all as magnetic, all as little fusible, and all as difficult of solution. Such was the result of the comparison I made on the sand of platina, and of the sand found in both my iron ores, at the depth of three feet, in earths where water easily penetrated. I was puzzled to conceive whence these particles of iron could proceed, how they had been defended against rust for the ages they were exposed to the humidity of the earth, and how this very magnetical iron had been produced in veins of mines, which had not the smallest degree of that quality. I called experience to my aid, and became at length satisfied upon these points. I was well convinced that none of our iron ores in grain were tractable by the loadstone, and well persuaded that all iron ores, which are magnetical, have acquired that property only by the action of fire: that the mines of the north, which are so magnetical as to be sought after by the compass, must owe their origin to fire, and are formed by the means, or the intermedium of water; from which I was induced to suppose that this ferruginous and magnetic sand, that I found in a small quantity in my iron mines, must owe its origin to fire, and having examined the place I was confirmed in this idea. This magnetical sand is found in a wood, where, from time immemorial, they have made, and still continue to make, coal furnaces. It is likewise more than probable that there were formerly considerable fires here. Coal and burnt wood produce iron dross, which includes the most fixed parts of iron that vegetables contain; it is this fixed iron which forms the sand here spoken of, when the dross is decomposed by the action of the air, sun, and rain, for then these pure iron particles, which are not subject to rust, nor to any other kind of alteration, suffer themselves to be carried away by the water, and penetrate with it some feet deep into the earth. What I here advance may be verified by grinding the dross well burnt, and there will be found a small quantity of this pure iron, which, having resisted the action of the fire, equally resists that of the solvents, and does not rust at all.

Being satisfied on this head, and having sufficiently compared the sand and dross taken from the iron ores with that of the platina, so as to have no doubt of their identity, it was not long before I was led to conclude, considering the specific gravity of platina, that if this pure iron sand, (proceeding from the decomposition of dross) instead of being in an iron mine, was found near to a gold one, it might, by uniting with that metal, form an alloy which would be absolutely of the same nature as platina. Gold and iron have a great affinity; and it is well-known that most iron mines contain a small quantity of gold; it is also known how to give to gold the tint, colour, and even the brittleness of iron, by fusing them together. This iron-coloured gold is used on different golden jewels to vary the colours; and this gold mixed with iron is more or less grey, and more or less tempered, according to the quantity of iron which enters the mixture. I have seen it of a tint absolutely like the colour of platina; and having enquired of a goldsmith the proportion of gold and iron therein, he informed me, that in a piece of 24 carats, there were no more than 18 gold, consequently a fourth part was iron, which is nearly the proportion found in the natural platina, if we judge of it by the specific weight; and this gold made with iron is harder and specifically less weighty than pure gold. All these agreements and common qualities with platina, have persuaded me, that this pretended metal is, in fact, only an alloy of gold and iron, and not a particular substance, a new and perfect metal different from every other, as chemists have supposed.

It is well known that alloy makes all metals brittle, and that when there is a penetration, that is, an augmentation in the specific gravity, the alloy is so much the more tempered as the penetration is the greater, and the mixture becomes the more intimate, as is perceived in the alloy called _bell-metal_, although it be composed of two very ductile metals. Now nothing is more tempered, nor heavier than platina, which alone ought to make us conclude that it is only an alloy made by Nature, a mixture of iron and gold, owing in part its specific gravity to this last, and, perhaps, also, in a great part, to the penetration of the two matters of which it is composed.