Page 10. "I examine the natural structure of some metals, I see certainly nothing more than that they are hard solidlyunited heavy bodies, which become liquid in the fire at different degrees of heat, and lose their former connectedness (or cohesion), and without being heavier take up a greater or less space than before. This is enough to enable us to conclude that the figure of the smallest particles of metals is changed by the fire, and that the fluid condition of the whole mass, and its altered specific gravity, are the necessary consequence of this alteration of figure. For when the mass of a body without change of weight takes up a greater or less space, it is certain that it can take place under no circumstances except a change of figure in the smallest portions of the bodies. A thousand small cubes may be put into a smaller space than the same number of spheres of the same mass and weight, and the heap made by the spheres is not so great as if they were converted into stars, and so on. When the specific gravity is altered, no matter by what means, the figure and situation of the smallest parts can no longer remain the same."

Page 20. "Besides change of figure, I know no sufficient reason for all that has been said; for if we completely banished the figure, and viewed the properties of the body as something substantial in matter, I know not how we could explain without contradiction the every-day experience; or we must, as Snellius with refraction, explain it by the will of God, which settles the matter at once; but if my understanding is to lay hold of the method by which anything acts, this explanation will not be satisfactory.

Page 28. "But we have remarked that any combination of bodies, on account of the figure of their parts, depends on static laws, and there it is proved that the motion of a weight is so much the slower the smaller the force is, in comparison with it. Let us apply this to the present case, and bodies will appear to us as so many weights, and their com

mon solvent as a force, which acts more slowly or more rapidly on one or the other. It follows, then, that the more rapidly a common solvent unites with a body, the greater must be its degree of combination, and we obtain therefore this law.

"The affinity of bodies with a common solvent is in the inverse ratio of the time taken to dissolve.

Page 31. "We have now a universal law, according to which the affinity of bodies or their rank in the series is decided, and we obtain at once this important advantage, that we not only know that the union of a common solvent is greater or less with any body, but also how much greater or less it is, because the difference of the time of solution shews the difference of the combination. Therefore amongst a number of bodies, the combination of one with a common solvent may be considered as a quantity which may be expressed by a fixed number, if we take the smallest in such a series as unity; and by this means we are able to give a correct explanation of all phenomena.

Page 46. “This important question, then, remains, why a solvent, when it is only moderately diluted, does not in the least attack certain metals, but as soon as another metal is dissolved in it, with which it naturally has a less affinity, a ready solution of the first takes place. Page 47. Because here the powers meet which assist each other.

Page 72. "The circumstances under which this metal (iron) is dissolved by vitriolic acid are these, that the acid must not be strong. When both unite, iron vitriol is formed, which loses the most of its acid in the fire, as well as by frequent solution in water. A small bored cylinder of Styrian steel of 102 grains was put into half an ounce of the spirit of vitriol, diluted with an equal quantity of water, exactly as with the zinc experiments; there remained 463 grains of steel, and 55 grains were dissolved in the half ounce of the spirit of vitriol.

"Therefore the relation of the hardest steel to the strongest vitriol is 175: 240.

"Application of the doctrine of affinity of bodies.* "This will best be shewn by examples.

"Is it possible by Beguin's spirit of sulphur (a sulphide of ammonium chiefly) to decompose the luna cornua, or to separate the muriatic acid entirely without loss ?"

"To settle this question we require only the following experiments. Muriatic acid has a smaller degree of affinity with silver than with the volatile salt. Sulphur, on the other hand, unites with silver in preference to the volatile salt. The silver is not separated from the muriatic acid by the volatile salt, on account of accidental circumstances, but this separation follows the moment any other body unites with the silver, if it has not the property of dissolving the silver. But sulphur is just such a body, and is, therefore, fitted for the purpose. If, then, the spirit of sulphur of Beguin is poured on finely powdered luna cornua, it is easily seen that the muriatic acid in the luna cornua must unite with the volatile salt in the spirit of sulphur, and the sulphur will unite with the silver. The new products that are formed by this separation, can consequently be nothing more than common sal ammoniac and sulphuretted silver.

Page 452. "Another similar question arises by which the proportions of the mixture must be considered. How much cinnabar must be mixed with the luna cornua, so as completely to separate the silver?

"The possibility of this decomposition may be shewn in the same way as in the first case. If no particular experiment is made, it depends on the comparison only of the following propositions. Half an ounce of luna cornua contains 180 grains of fine silver. Half an ounce of fine silver takes up 35 grains of sulphur. We may then calculate that for 180 grains of fine silver, 26 grains of sulphur are required. We know besides, * Page 450.

that cinnabar contains sulphur in the proportion of 65 to 240 of quicksilver, or 65 grains of sulphur united with 240 of quicksilver, are to be met with in 305 grains of cinnabar, therefore 26 grains of sulphur are contained in 1251⁄2 of cinnabar. This quantity of cinnabar, as regards its sulphur, will be sufficient for the decomposition of half an ounce of luna

cornua.

"But we must inquire if 125 grains of cinnabar contain as much quicksilver as will be sufficient to take in the muriatic acid which is saturated with the silver. Half an ounce of luna cornua contains 53% grains of muriatic acid of greatest concentration. In half an ounce of the caustic sublimate there are 58 grains of the strongest acid, which is saturated with 174 grains of quicksilver. From this proportion it is found that 53 grains of the strongest muriatic acid are required for 159 grains quicksilver. Now as there are in cinnabar 240 grains of quicksilver united with 65 grains of sulphur, 159 grains of quicksilver require 43 grains of sulphur. Both together give nearly 2021 grains of cinnabar. Consequently, from 125 grains of cinnabar, all the muriatic acid found in the luna cornua is not separated. We see from this that the muriatic acid of the lunar caustic rises in sublimation with the quicksilver out of the 202 grains of cinnabar as a caustic sublimate, whilst the silver remains united only with so much sulphur as it found in 125 grains of cinnabar."

His smallest parts of bodies are not atoms, but molecules rather, or particles, as they change their form.

He has made a theory of affinity, and attempted to represent the force by a number. To attempt to give the numerical or dynamical ratio of every body to each other was an object of the very highest kind, and we must look on him as one of those less fortunate men who, when search was required in every direction, has had the misfortune to have the wrong one assigned to him. He searched in the direction of time, and obtained a manifest fallacy; as bodies are constituted abstractly

he might be correct, but his theory cannot be introduced into science at present, and in the way he introduced it, it was entirely a mistake. But he has done great service in early times in seeking for the distinct constitution of bodies, and in asserting the constancy of combination; whilst he obtained numbers representing the constant relation of bodies to each other, he failed to see that they would be reciprocal. This failure at once removes him from the great discoverers, and places him among those honourable and valuable labourers in science whose names are read with respect by students, but who cannot be recognised by mankind generally, because the capacities of our minds are too small to retain more than the lives of a few of the most eminent.

The doctrine of reciprocal proportion must be taken from him, and he can now no longer hold a place in the history of the atomic theory other than as the author of an intelligent attempt which has entirely failed.

I feel sorry to leave him in this state, and a few kind words will do little good. I believe he would have preferred the truth; the honour he received was not required by him; the discovery was not claimed by him; he died in 1793, before it was known to be worth making. In his works he appears an honest, earnest man.