IV. "Homer and Hesiod, whom we own great doctors of theology, V. "All eyes, all ears, all thought is God, the omnipresent soul, And free from toil, by force of mind he moves the mighty whole.” The only other point worthy of remark with regard to Xenophanes is that he seems to have been the first Greek speculator— certainly the first of whom any record is left-who distinctly noted those curious phenomena in the crust of the earth's surface indicative of an early disturbed state of the globe, which, when collected and systematized, have grown up into the interesting modern science of Geology. The passage in which this remarkable notice occurs is in that part of the work of Hippolytus (Refut. Hær., i. 14) which gives a review of the opinions of the Greek philosophers; and here he distinctly says that "shells, and the prints of fishes, and marine animals were found in the rocks at Syracuse, Malta, and Paros; and that this was evidently the result of a revolution of the Earth's surface, when everything was swathed in mud, and the living creatures of the sea left the impressions of their bodies in the soft beds, which afterwards became dry." The last philosopher whom our present scheme requires us to mention is Anaxagoras, the friend of Pericles, and the precursor of Plato in the complete emancipation of metaphysical speculation from physical symbols. No doubt Socrates in a well-known passage accuses this philosopher of not having consistently applied the intellectual principle of the world which he laid down (Plat. Phæd. 98 B.); but in declaring that the only adequate explanation of the cosmos was to be found in self-existent self-energizing vous or MIND, Anaxagoras certainly made a stride in advance, marking him out as well worthy of the commendation bestowed by Aristotle, that in this matter he spoke like a full-grown man as contrasted with the lisping and babblement of children. There is in fact only a very superficial difference of expression between the vous of Anaxagoras and the ELOHIM of Moses. "In the beginning GoD created the Heaven and the Earth." About the exact meaning of the word "create (Bara), of course our finite intellects always must dispute: if we could understand that word fully, we should be not men, but God: apart from this, however, the Baixos vous of Anaxagoras and Plato, which is the keystone of Christian faith as well as of the highest modern thinking, is simply another name for sós-GOD. We find, therefore, in the apn of Anaxagoras a natural and beautiful culmination which harmonizes in one significant watchword the philosophy of Greece, the faith of Christendom, and the instincts of a healthy humanity. Of the sophists as predecessors or contemporaries of Socrates it is not necessary to say anything in this paper. They were not so much founders of systems of philosophy as disputers about philosophy corresponding to a certain class of our literary men, who talk and write on all subjects without having any strong convictions on any subject; some of them, indeed, as Gorgias, professing only to be teachers of rhetoric, and others adding to that some superficial instruction in the principles of a worldly morality and a time-serving statesmanship. The philosophy that they taught was generally of a negative and destructive character; and the part which it played in the history of thought was mainly to bring out in full armed strength the rational ethics of Socrates, Plato, and Aristotle. Of course I am fully aware of the attempt recently made by Mr. Grote to plant these gentlemen on a higher and more dignified platform; but great as are the merits of this distinguished writer in reference to the political history of Grecce, I cannot but regard his chapter on the sophists as the product of a reactionary feeling, doomed to pass away with the generation which gave it birth. [J. S. B.] WEEKLY EVENING MEETING, Friday, April 28, 1871. SIR HENRY HOLLAND, Bart. M.D. D.C.L. F.R.S. President, WILLIAM ODLING, M.B. F.R.S. FULLERIAN PROFESSOR OF CHEMISTRY, ROYAL INSTITUTION, On the Revived Theory of Phlogiston. ... Observationem, quam produco, bono jure mihi vindico. Materia hæc ignescens, in omnibus tribus regnis, una eademque existit. Unde, ut e vegetabili in animale, abundantissime transmigrat, ita ex utrolibet_horum, in mineralia et ipsa metalla, promptissime omnium transfertur.-STAHLII, Experimenta, Observationes, Animadversiones, CCC Numero. IN 1781-83, Cavendish showed that when inflammable air or hydrogen, and dephlogisticated air or oxygen, are exploded together in certain proportions, "almost the whole of the inflammable and dephlogisticated air is converted into pure water," or as he elsewhere expresses it, "is turned into water." On June 24, 1783, the experiment of Cavendish was repeated on a larger scale and in a somewhat different form by Lavoisier, who not only confirmed the synthesis of the English chemist, but drew from it the conclusion-at first strongly contested, then rapidly acknowledged, and since never called into question--" that water consists of inflammable air united to dephlogisticated air," or that it is a compound of hydrogen and oxygen. This conclusion, so opposite to his own preconception on the matter, Lavoisier subsequently confirmed by an analysis of water. He found that iron, heated to redness and exposed to the action of water-vapour, became changed by an abstraction of oxygen from the water, into the self-same oxide of iron procurable by burning the metal in oxygen gas,-the other constituent of the water, namely, its hydrogen, being freely liberated. With the demonstration by Lavoisier of the composition of water began the triumph of that antiphlogistic theory, which he had conceived, in a necessarily imperfect form, so far back as 1772, or before the discovery of oxygen, and had brought to completion by the aid of every successive step in pneumatic chemistry, achieved by himself or by others. In 1785, the relationship to one another of hydrogen and water being then conclusively established, Berthollet declared himself a convert to the new theory of combustion put forward by his countryman. Fourcroy next gave in his adhesion; and soon afterwards De Morveau, invited to Paris expressly to be reasoned with by Lavoisier, succumbed to the reasons set before him. The four chemists then associated themselves together, and in spite of a strong though shortlived opposition both in England and Germany, succeeded in obtaining for La Chimie Française an all but universal recognition. The principal articles of the new or antiphlogistic theory of combustion propounded by Lavoisier are as follows:-That combustible bodies in burning yield products of various kinds,--solid in the case of phosphorus and the metals, liquid in the case of hydrogen, gaseous in the case of carbon and sulphur. That in every case the weight of the products formed by the burning is greater than the weight of the combustible burnt. That the increase of weight is due to an addition of matter furnished to the combustible by the air in which its burning takes place. That bodies of which the weights are made up of the weights of two or more distinct kinds of matter are of necessity compound; whereas bodies of which the weights cannot be shown to be made up of the weights of two or more distinct kinds of matter are in effect simple or elementary. That inasmuch as the weights of the products furnished by the burning of different combustibles are made up of the weights of the combustible burnt and of the oxygen consumed in the burning, these products are compound bodies--oxides in fact of the substances burnt. That inasmuch as given weights of many combustibles, as of hydrogen, sulphur, phosphorus, carbon, and the metals, are not apparently made up of the weights of two or more distinct kinds of matter, these particular combustibles are in effect elementary; as for the same reason is the oxygen with which in the act of burning they enter into combination. And, lastly, that combustion or burning consists in nothing else than in the union of combustible matter, simple or compound, with the empyreal matter, oxygen the act of union being somehow attended by an evolution of light and heat. And except that it would be necessary nowadays to explain how in certain cases of combustion, the combustible enters into union not with oxygen, but with some analogue of oxygen, the above precise statement might equally well have been made by Lavoisier in 1785, or be made by one of ourselves at the present day. Lavoisier's theory of combustion being known as the antiphlogistic theory, the question arises, What was the phlogistic theory to which it was opposed, and which it succeeded so completely in displacing? This phlogistic theory was founded and elaborated at the close of the seventeenth century by two German physicians, Beccher and Stahl. Having exercised a scarcely disputed authority over men's minds until the notorious defection in 1785, it preserved for some years longer a resolute though tortuous existence, and was to the last defended and approved by our own Priestley and Cavendish-who died, the former in 1804, and the latter in 1810. The importance attached to the refutation of this theory may be judged of from the circumstance that after the early experiments of Lavoisier on the composition and decomposition of water had been successfully repeated by a committee of the French Academy in 1790, a congratulatory meeting was held in Paris, at which Madame Lavoisier, attired as a priestess, burned on an altar Stahl's celebrated Fundamenta Chemia Dogmatice et Experimentalis, solemn music playing a requiem the while. And the sort of estimation in which the Stahlian doctrines have since been held by chemists is fairly illustrated by a criticism of Sir J. Herschel, who, speaking of the phlogistic theory of chemistry, says that it "impeded the progress of the science, as far as a science of experiment can be impeded by a false theory, by involving the subject in a mist of visionary and hypothetical causes in place of the true acting principles." Possibly, however, this much-abused theory may yet prove to contain an element of permanent vitality and truth; anyhow the study of this earliest and most enduring of chemical theories can never be wholly devoid of interest to chemists. To appreciate the merit of the phlogistic theory it is necessary to bear in mind the period of its announcement. Its originator, Beccher, was born in 1625, and died a middle-aged but worn-out man in 1682, a few years before the publication of the Principia.' His more fortunate disciple, Stahl, who was born in 1660 and died in 1734, in his seventy-fifth year, though afforded a possibility of knowing, seems equally with Beccher to have remained throughout his long career indifferent to the Newtonian principle that the weight of a body is proportionate to its quantity of matter-that loss of weight implies of necessity abstraction of matter, and increase of weight addition of matter. Whether or not the founders of the phlogistic theory conceived that change of matter in the way of kind, might equally with its change in point of quantity, be associated with an alteration in weight and it must not be forgotten what pains Newton thought it necessary to take in order to show the contrary-certain it is they attached very little importance to the changes of weight manifested by bodies undergoing the metamorphosis of combustion. It might be that when combustible charcoal was burned the weight of incombustible residue was less than the original weight of charcoal-it might be that when combustible lead was burned the weight of incombustible residue was greater than the original weight of metal-this was far too trifling an unlikeness to stand in the way of the paramount likeness presented by the two bodies. For the lead and charcoal had the common property of manifesting the wonderful energy of fire; they could alike suffer a loss of light and heat-that is, of phlogiston-by the deprivation of which they were alike changed into greater or less weights of inert incombustible residue. And not only were these primitive students of the philosophy of combustion unconscious of the fact and meaning of the relationship in weight subsisting between the consuming and the consumed body, but they were altogether ignorant of the part played by the air in the phenomena which they so boldly and successfully attempted to explain. Torricelli's invention of the barometer and Guericke's invention of the air-pump were both indeed made during Beccher's early boyhood; but years had to elapse before the consequent idea of the materiality of air could be domiciled, as it were, in human understandings. And not until more than a century after Torricelli's discovery of the weight of air,-not, indeed, until the time of the great pneumatic chemists Black, and Cavendish, and Priestley, and Scheele, was it ever imagined that the aerial state, like the solid or liquid state, was a state common to many distinct kinds of matter; and that the weight or substance of a rigid solid might be largely contributed to by the weight or substance of some constituent having its independent existence in the aerial or gaseous form. The notion that 100 lbs. of smithy-scales might consist of 73 lbs. of iron and 27 lbs. of a particular kind of air, and that 100 lbs. of marble might consist of 56 lbs. of lime and 44 lbs. of another kind of air, was a notion utterly foreign to the older philosophy. Air, it was allowed, might be rendered mephitic by one kind of contamination, and sulphurous by another, and inflammable by a third; it might even be absorbed in, and so add to the weight of, a porous solid, as water is absorbable by sand; but still air was ever indisputably air, essentially alike and unalterable in its mechanical and chemical oneness. This familiar conception had to be overcome, and the utterly strange notion of the largely aerial constitution of solid matter to be established in its stead, by the early pneumatic chemists, Black, and Cavendish, and Bergmann, before the deficiencies rather than positive errors of the phlogistic theory could be perceived. But long ere the foundation of modern chemistry had thus been laid, in 1756, by Black's discovery of fixed air or carbonic acid as a constituent of mild alkalis and limestone, those old German doctors, Beccher and Stahl, though ignorant of the nature of air and neglectful of the import of gravity, had yet found something to say about |