"THIS must have afforded much amusement to Mr SMELLIE, who was himself the author of that article; as my father soon learned from Mr SMELLIE; for he was so much piqued at Dr CULLENS unjust and ungenerous suspicion, that he spared no pains to discover the real author of that well written but severe article, which had given such offence, and been so rashly imputed to him. Mr SMELLIE, for good reasons, did not choose to be generally known as the author of it at that time; but I know that, in the course of some years afterwards, Dr CULLEN found him out, and was very angry at him accordingly. That discovery of Mr SMELLIE being the author of it, I have always understood, gave occasion to the complete alteration and softening of the article Æther in the second and all the subsequent editions of the Encyclopedia; so that nothing of it was allowed to remain that could give offence to Dr CULLEN."

It has been alleged that the circumstance which weighed most with Dr CULLEN in being angry on the subject, was, that certain godly ministers of Edinburgh had taken the a

larm at Dr CULLENS doctrine, and impressed an idea on some good ladies that it was unorthodox. Dr CULLEN therefore was apprehensive that it might injure his medical practice among the leading ladies of Edinburgh. We are far from wishing to impute any sinister motives to the reverend clergy who bestirred themselves on this occasion, to repress what they considered as heterodox doctrines. We know that the order is generally most respectable, and contains an uncommon number of learned, ingenious, and liberal men. But some well-meaning members of that numerous and respectable body are apt occasionally to embrace confined views in science and philosophy with a too hasty zeal, as was the case on the occasion here alluded to. The article respecting Ether is ingenious; and the publication in which it appeared having been long superseded by more extensive editions, it has been deemed worthy of being reprinted in this place. It gives a striking instance of Mr SMELLIES acute discernment, and strict philosophical induction; which otherwise is now in a manner hidden from the world in that obsolete edition of the Encyclopedia.

• ETHER, the name of an imaginary fluid, supposed by several authors, both ancient and modern, to be the cause of gravity, heat, light, muscular motion, sensation, and, in a word, of every phenomenon in nature. ANAXAGORAS maintained that æther was of a similar nature with fire; PERRAULT represents it as 7200 times more rare than air; and Hook makes it more dense than gold itself. Whoever has an inclination to know the various hypotheses concerning æther may consult SHEBBERE, PERRAULT, Hooks posthumous works, Act. Erud. Lips. 1716, BERNOUILLIS Cogitat. de gravitate ætheris, &c. &c.

BEFORE the method of philosophising by induction was known, the hypotheses of philosophers were wild, fanciful, ridiculous. They had recouse to æther, occult qualities, and other imaginary causes, in order to explain the various phenomena of nature: But since the days of the great Lord VERULAM, who may be styled the parent of genuine philosophy, a contrary course has happily been followed. He convinced the world, that all knowledge must be derived from experiment and observation; and that every attempt to investigate causes by any other means must be unsuccessful. Since his time, the best

philosophers have followed the tract which he pointed out. BOYLE, LOCKE, NEWTON, HALES, and a few others, in little more than one century, have improved and extended science far beyond what the accumulated force of all the philosophers since the creation had been able to effectuate: A striking proof both of the comprehensive genius of BACON, and of the solidity of his plan of investigation.

It must indeed be acknowledged, that there is a propensity in the human mind, which, unless it be properly restrained, has a direct tendency both to corrupt science, and to retard our progress in it. Not contented with the examination of objects which readily fall within the sphere of our observation, we feel a strong desire to account for things which, from their very nature, must, and ever will, elude our researches. Even Sir ISAAC NEWTON himself was not proof against this temptation. It was not enough that he had discovered the nature of light and colours, the application of gravity to the motions of the heavenly bodies, &c. he must go further, and attempt to assign the cause of gravity itself. But, how does he proceed in this matter? Not in the way of experiment,

which had led him to his former discoveries, but in the way of conjecture, which will never lead any man to truth. He had recourse to a subtile elastic æther, not much different from that of the ancients, and by it accounted for every thing he did not know, such as the cause of gravitation, muscular motion, sensation, &c.

NOTWITHSTANDING the reputation of Sir ISAAC, philosophers have generally looked upon this attempt as the foible of a great man, or, at least, as the most useless part of his works; and accordingly peruse it rather as a dream or a romance, than as having any connexion with science. But we are sorry to find that some late attempts have been made to revive this doctrine of æther, particularly in a dissertation De ortu animalium caloris, published in May 1768.

As the revival of an old doctrine becomes in some measure a new one, we shall plead no other apology for inserting a specimen of the method of reasoning employed in this dis

sertation.

THE author makes frequent use of a species of argument termed dilemma by logicians.