"motion. Nor is this a bare speculation, depending "on such principles as must be committed to the "courtesy of the reader; for the thing is reducible "to practice. “ "Air is a resisting medium; yet instead of retarding the motion of the lamp-machine by its "resistance, it preserves that motion by its impulse. "And if the motion is discontinued at last, this is "not owing to any defect or irregularity in the "cause, but to the imperfection of the materials. If "the materials, which are acted upon, would but "continue in the same state, the motion would be "unretarded, so long as air and fire, which are the "causes of it, subsist in the world. "In this experiment, the causes are not artificial "and violent, as when a circular motion is given to "a stone whirled about in a sling, or to bullets "carried about in a box by the revolutions of a centrifugal-table, &c. but such as are supplied by "nature itself, in its regular method of acting; which both begins, and continues the motion. "What is done by nature in one case, may certainly be done in others. The planets themselves may be carried round in their orbits, by the same "means. The heavens may be filled throughout "with an ætherial fluid; not infinitely rarefied, "unresisting, and impotent; but dense, and con❝tinuous in its parts: for if such a fluid is contrived, "by the great Author of nature, to govern and "regulate the planetary motions; never let us fear, "that it will obstruct and retard the motion which "it gives. From all this, we have sufficient reason "to conclude, that the operations of nature may be "mechanical. "Nor is it less evident that they really are so. "In all those experiments, where there, can be no "reasonable doubt about the explanation, matter is "found to act upon other matter, for the producing "of the effect; and we are able to trace this in "such a variety of instances, that unless the world' "is governed by opposite and contradictory prin"ciples, the same rule must obtain throughout the "whole. The body of man, which is the highest "piece of machinery in nature, is made to see, and "hear, and speak, upon mechanical principles; and "it dies without the constant impression of a material force upon it from the element of air. By the pressure of this air, the Mercury is made to rise "in the tube of a barometer; hail, snow, and vapours, are formed in the atmospherical regions, by the different temperatures of it: the clouds "are sustained by it, and driven about to water the "earth plants grow and are nourished by it: "without it, there could be neither sound, voice, "nor language: all fires would be extinct: all "animals, whether fowls, beasts, or fishes, would perish; and the whole world would languish and "decay." ་་ "These are the instruments (fire and air) which "God hath manifestly ordained, as secondary and "subservient to his own power, in the economy of "the material world: and they are so universally “extended, and incorporated with other things, as "to be serviceable in the motion of all its particular "parts. Some or other, and in many cases each "of these, are present to all those effects which "have fallen under the observation of philosophers; " and there are no other causes to be found; unless we ascribe unintelligible and innate powers to "inert matter, thereby making the effect to be the "cause of itself; or can suppose, against the dic"tates of reason and common sense, that God, who "hath created these means, hath made it a rule to "act without them. Of these, both art and nature "receive the benefit in common. What strange things are brought to pass by every ordinary "blacksmith, only by the application of fire and "air from his forge and his bellows? If he turns 66 66 "these out of his shop, the strength of his hands "will do him but little service; and the rest must "be left to attractions and repulsions: but iron and "brass do not understand the force of such philo"sophy. What would the chemist do, without his "furnaces and his refrigeratories? Hence proceed "all his separations, sublimations, condensations, "fixations, digestions, chrystallizations, and such "like. With the help of these natural causes, very "few things are too hard for him; but without them, his whole art would be at a stand. The "chemist sees this and confesses it he cannot but "observe the uses of fire and air within the sphere "of his laboratory; and is thence naturally led to " acknowledge their uses in the greater operations "of nature. Hence it comes to pass, that there "are very few chemical writings extant, which will "not afford some light to a natural philosopher; "but above all others, the writings of Dr. "Boerhaave ought to be valued upon this account. 46 "What fruit then can be expected from the "labours of any disquisitor, where he neglects "these elements, and would banish them, to make way for such causes only as can operate in a "vacuum? He must of course deface the chief "beauty of nature; which is no where so con"spicuous, as in the dependence that is established "between effects and their causes; and must empty "the world of its matter and mechanism, only to "fill it with difficulties and mysteries. If he "destroys the connexion between the parts of "matter, he inust present us with such a picture of "nature, as can resemble nothing but the bones of a skeleton, which cannot stir one step upon "natural principles: whereas the work of God is "worthy of its author, and the frame of nature is a "perfect and well connected-body, furnished with "all its proper muscles and ligaments. The bones "are united, moved, and lifted by the muscles: if "an anatomist, in describing the wonders of the "human frame, should leave out these, he must suppose the bones to move themselves; after "which, he might go on to argue against the "muscles, as things useless and unnecessary, mere "obstacles to the free and easy motion of the bones "within their sockets; and then he would philoso"phize just as they do, who forget that fluid "matter of the Heavens, by which all other things "are moved and connected together, and place "occult powers in the solid matter of the celestial "orbs."-P. 180. The zodiacal light may be nothing more than the first lighting up of the atmospheric air, being acted on by the earliest approach of the Sun's influence, on reaching those parts. 3 PART III THE TIDES. IN stating any proposition which is self-evident, it should be sufficient to lay the particulars of it before the public, without animadversions on former contrary opinions; but prejudice is a propensity which has the appearance of being inherent in the human mind, like a second nature; this is manifest, by observing how a favorite opinion is supported, whether it is in religion, politics, philosophy, or any of the minor occupations in which man is engaged, so that the bright side of any question is only looked to by its supporters, who rarely suffer themselves to be moved from their point of view; by these means, many truths are suffered to lay dormant, the generality of the world being satisfied in their conclusions as handed to them by their progenitors and instructors. cording to this, it happens, that specious arguments are produced in support of untruth; blending plausibility in a labyrinth of sophistry, whereby the principle of the matter in question, is lost sight of, and nothing but the shadow is left. Ac That such has been the case, in respect of accounting for the causes of the Tides, I shall endeavour to make appear, and in doing which, I shall, without descending to the particulars of subordinates, abide by the generally received opinion of the influence of attractive or gravitating power; which will carry every minor consideration with it. I believe Kepler to have been the first who offered any thing like a theory, for the causes of this phenomenon. He found out that the Moon was within the reach of the Earth's influence, so he |