As for the Greek philosophers, there is not one of the doctrines for which our modern philosophers receive so much credit as their original inventors and discoverers, which has not been amply discussed by the Ionic school, the Italic school, or the Eleatic school. Let those who doubt this turn to Diogenes Laertes, or to the dialogues of Plato, in which Socrates is the chief speaker. If neither Laertes nor Plato will be regarded as sufficient authority, then turn to any modern critic worthy of the name who has undertaken to analyze the system of the Greeks. None can be regarded as better authority than Frederick Schlegel. "The doctrine of mechanical union," says the great German critic, "had been completely systematized by those early Greeks, Leucippus and Democritus, and in the later teaching of Epicurus had exercised an influence over both Greeks and Romans in a degree equal to its sway in the eighteenth century."* Referring to the doctrine of constant mutation, which we are informed is another wonderful discovery of our modern philosophers, Schlegel proceeds: "One section of these ancient philosophers, whilst differing on various points, had this in common, that they looked upon nature purely on the side of its perpetual change and motion. They held that all things were in a constant flux. They carried this assertion so far as to deny that anything was fixed and permanent they denied that anything was stable in existence," etc.†

So much, then, for the novelty and originality of those theories and doctrines which we are called upon to regard as so many conclusive evidences of the immense intellectual progress of the present day, and of the increasing profundity and acumen of our innumerable philosophers!—ED. N. Q. R.]

It is our object in this article to consider only the changes which have taken place in the science of Chemistry, a subject so wide in its scope that we have only space for a rapid glance at it alone. It seems strange to speak in these terms of that which, as a science, was born just a century ago. Nothing is

*Lectures on the Hist. of Lit., Ancient and Modern. Bohn's edition, p. 42. ↑ Ibid, p. 43.

more significant of the intellectual activity of the nineteenth century than to find a science of the widest affinities, and of facts innumerable, progressing through a number of intricate and apparently stable and satisfactory theories within the space of a hundred years. Text-books have proved quite unable to keep pace with its progress. The most of those now in existence are based on a condition of the science which has passed away. Their observed facts are alone reliable; their theories, their nomenclature, their conclusions, their general position, are calculated to mislead the student, and to teach him that which he will be obliged to unlearn if he wishes to continue his studies.

No chemist at the present day is half so sure of his position as were those of twenty or thirty years ago. Though the science has really assumed a much more stable and coherent form than it ever before attained, and though numerous facts fit readily into the existing hypotheses which no ingenuity could reconcile to the old standards, yet scientists have beheld so many fair-seeming edifices falling into ruin, and behold before them such a wide vista of approaching discovery that they are much less inclined than in the earlier days of the study to accept as facts any theoretical views.

One thing is granted. Many of the old theories are dead, no matter what fate may befall those which have taken their place. The discovered facts in chemistry are numbered by hundreds, and any theoretical arrangement which is capable of taking these disconnected facts, marshalling them into ranks, in which each fact finds its appointed place, and out of the confusion bringing an order which is full of the elements of beauty and grandeur, is likely to be far on the road towards truth, even though it be not the full truth itself. Such a position chemical theory has assumed, and we are enabled, through the employment of this instrumentality, to handle a multitude of facts which otherwise could not be brought into any coherent or manageable order.

It is not alone the chemistry of inorganics with which we have now to deal, referring organic chemistry to the action of a hypothetical vital force which removes it out of our

reach. The handling of the simple inorganic compounds was easy compared with the innumerable and highly complex organic combinations. But we can no longer consider them separately. The wall between them has been utterly broken down and trodden under foot by eager climbers up the hill of science. The temple of chemistry must now have niches for every fact, in both kingdoms of the science, ere it can be viewed as complete and firmly founded.

In speaking of Chemistry as being but a century old, reference is made simply to its scientific standing. As a collection of discovered facts it dates much further back. The ancient nations had considerable knowledge of its more evident details, and these were taken up and largely increased by Arabian investigators during the middle ages. European scholars took up their facts and continued to add to them," some little speculation being indulged in, but nothing approaching the coherence of a system being devised. The facts, as yet, were not sufficiently numerous and connected to permit the discovery of their relations. The only attempt at theory that attracted any special attention was that of Stahl, in his phlogistic theory of combustion. This hypothesis, which could only hold ground through the ignorance and partial habit of investigation of its adherents, was worked out with considerable ingenuity, and was adhered to with a persistence worthy of a better cause, by such men as Priestly, Cavendish, and Scheele, even after it had received its death blow at the hands of Lavoisier. Yet the first of these scientists, in his discovery of oxygen, furnished the lever for the overthrow of the theory to which he continued determinedly to adhere.

Lavoisier then was the true father of the existing science of chemistry. He first applied the balance to the products of combustion, and argued that the greater weight of these products was inconsistent with the belief in the loss of the supposed substance called phlogiston. On the contrary the substance had gained, while the air had lost to the same extent. There was plainly a combination instead of a decomposition.* *Opuscules, p. 247.

The discovery of oxygen added substantial force to his theory. It was soon found that this was the constituent of the air that disappeared in combustion, and the important fact, which stands at the threshold of the science of chemistry, was fully announced, that combustion is a process of combination between oxygen and the elements of combustible bodies, and that the light and heat emitted are the results of an elevation of temperature produced by the chemical action. This theory, which seems so simple to us, was then utterly strange and difficult of acceptance to scientists. It was enunciated just a century ago, and from that moment chemistry took rank with the sciences.

We will briefly glance at the further progress of chemical theory, before describing the happy generalizations which now combine its multitude of facts into a coherent, and in great measure, complete system. As to the succession in the discovery of important facts, we cannot attempt to enter this immense field. After the discovery by Lavoisier of the true principle governing combustion he turned his attention to the subject of the formation of salts, announcing the following definitions: An acid results from the union of a simple body, generally non-metallic, with oxygen. An oxide is a combination of metal and oxygen. A salt is formed by the union of an acid with an oxide. These simple propositions formed the

basis of a new system of chemistry.*

The principles thus announced as governing oxygen compounds were easily applied to compounds of the other chemical elements, and from them was gradually worked out the proposition which forms the distinguishing feature of the system of Lavoisier, and which long reigned dominant in the chemical world. This is, that all chemical compounds are binary. In all compounds the affinity acts between two elements, simple or compound. These are attracted together and unite through a certain opposition of properties, which is neutralized by the act of combining. We have here, in few words, the dualistic theory, which had its utility in the infancy

* Wurtz, p. 18.

of the science, and which long held sway in the minds of chemists.

To the above theory the newly established nomenclature, first suggested, in 1782, by Guyton de Morveau, was adapted. This skilfully devised language, so clear as to remarkably facilitate the study of the science, and so full of fertile expedients for the introduction of all its intricate facts, had for its basis the dualism of compounds. Thus, since the year 1790, in which it was fully adopted, the dualistic idea has been insinuated into the mind of the student, in the language of chemistry. We know enough of the power of words to know how greatly this must have aided in its retention.

At the same period a German philosopher, Wenzel, was announcing ideas pointing forward to the doctrine of chemical equivalents. Twenty years later Richter took up and developed this law. Yet their labors were allowed to fall into oblivion. They were too incomplete, and too far in advance of their time for acceptance.

But a greater mind than these, that of Dalton, forced similar views upon public attention, adding to the doctrine of definite equivalents that law of combination in multiple proportions, which forms in its entirety the most important discovery ever made in chemical science. Reviving the old Greek idea of atoms he gave it a fixed and definite meaning. He claimed that bodies are composed of small individual particles, which he called atoms. These are of definite size and weight for each element, and the process of combination means simply the union of atoms of different substances into compound atoms. The law of multiple proportions indicated that the atom of one substance might combine with one, two, three, or more, of another substance. This theory had its opponents to master, but it so clearly elucidated the prin cipal mysteries of the science, as then existing, that it was not long in forcing itself into general acceptance.

The next great discovery which aided largely in the progress of chemical science was that made by Gay Lussac, and worked out by him and A. Von Humboldt in 1805. This was the discovery of the fact that substances in a gaseous