latter, of Modelling, Perspective, Engraving, and Painting. But though those subjects are treated in a concise, and sometimes in a superficial manner; yet they furnish good examples of the application of mechanics, and serve, at the same time, to relieve the mind from the continual attention to theoretical precepts. Nearly the same observations are applicable to the fourteenth lecture, wherein the principles of architecture and carpentry are explained, and to the seventeenth, which describes the construction of chronometers, or time-keepers, giving an account of their gradual improvements, and their peculiar merits. The twentieth lecture, which contains a concise history of Mechanics, and concludes the first grand division under the name of Mechanics, is peculiarly well adapted to the inclination of general readers. There is a competition, -a sort of rivalship, among human beings, which renders them extremely fond of personal anecdotes. The unusual actions, whether laudable or blameable, of other individuals, their prosperity, or their misfortunes, seldom fail to excite interest and curiosity; for by a natural application to ourselves, our satisfaction, our emulation, our caution, or our astonishment, is called forth, whence new actions frequently arise. In scientific histories, where theoretical or practical subjects are connected with personal anecdotes, the latter, by a natural connexion of ideas, help to impress the former on the mind of the hearer. Thus the idea of burning-glasses generally suggests the remembrance of Archimedes, and Proclus, who are said to have burned the vessels of their enemies by means of reflectors. Thus also the name of Newton is scarcely separable from the idea of the general gravitation of matter. Dr. Young begins his lecture with the origin of Grecian learning in Egypt, and then proceeds to mention the Ionian and the Italian schools, Pythagoras, Democritus, Archytas, Aristotle, Epicurus, Archimedes, Vitruvius, Bacon, Galileo, Napier, Newton, Hooke, &c. down to the most modern pltilosophers, mathematicians, and mechanics. The sketch is concise, but regular and instructive. A short table is placed at the end of the lecture, exhibiting the names of the abovementioned, and other ingenious persons, with the periods in which they lived, after the manner of Priestley's biographical table. A similar appendage is added to each of the other historical lectures. From this twentieth lecture the following paragraphs are transcribed as a specimen of this author's style. "In the midst of an age of darkness, an insulated individual " arrests our attention, by merits of no ordinary kind. Roger "Bacon was born at Ilchester, in the year 1214: it is well known "that his experiments had led him to a discovery of the properties " of gunpowder, although he humanely concealed the nature of its " composition from the public, and described it only in an enigma. "The extent of his optical knowledge has been variously estimated, " but it was unquestionably much greater than that of the ancient " philosophers. He appears, however, to have had some com "panions in his mechanical pursuits; he declares that he had seen "chariots which could move with incredible rapidity, without the " help of animals; he describes a diving bell: and he says that he " had been informed, on good authority, that machines had been "made, by the assistance of which men might fly through the "air. Cimabue, who first began to revive the long neglected art " of painting, was contemporary with Bacon. The use of oil in "painting is commonly supposed to have been introduced by "Van Eyck; but there are traces in the records of this country, " of its employment as early as the year 1239." "The clepsydræ, or water timekeepers of the ancients, ap. "pear to have been gradually transformed, in the middle ages, " into the clocks of the Saracens, and of the Arabians; and these " were introduced into Europe in the thirteenth century. About "the year 1290, turret-clocks were erected at Westminster, and at "Canterbury. The first clock, of which we know the construc"tion, is that which was made by Wallingford in 1326, and which " was regulated by a fly; and the second that of Defondeur, or "Fusorius, with a simple balance, made about 1400....But it " appears that some portable watches had been constructed in the "beginning of the fourteenth century; and about the year 1460, "several clock-makers are said to have come to England from " Flanders." "The art of engraving on metal, and of printing with the rol. "ling press, is supposed to have been invented in the year 1423. "Some attribute the art of printing with types to Laurentius "Coster, of Haerlem, who, as they say, in 1430, employed for the purpose separate blocks of wood, tied together with thread. "Gensfleich, one of his workmen, went to Mentz, and was there "assisted by Gutenberg, who invented types of metal. But the "best authors appear to disbelieve this story; and Gutenberg, in "partnership with Fust, and Schoeffer, is the first that is univer. "sally allowed to have practised the art. It was introduced into "this country by William Caxton." "Leonardo da Vinci, the most accomplished man of his age, " was born about the year 1443, and excelled not only in painting "and poetry, but also in architecture, mathematics, and mechanics. "The state of practical mechanics in this and the subsequent cen"turies may be estimated from Ramelli's collection of machines, "which contains several curious and useful inventions; some of "them long since forgotten, and even lately proposed again as new." "The works of Bacon, Lord Verulam, although not immedi"ately tending to the advancement of mathematics or mechanics, are universally allowed to have conduced very materially to the "improvement of every branch of science, by the introduction of a correct and conclusive method of philosophical arrangement "and inquiry. Guido Ubaldi published, in 1577, a treatise on " mechanics, not wholly exempt from inaccuracies; and in the fol"lowingyear, a valuable commentary on the works of Archimedes: some of the properties of projectiles were about the same time " rather imagined than demonstrated by Tortalez: Benedetti soon "after began to reason correctly respecting the principles of me"chanics; but it was reserved for Galileo to lay the foundations " of the discoveries, which have succeeded each other with increa. "sing rapidity for more than two centuries. He investigated, in "the year 1589, the laws of accelerating forces, and shewed the "nature of the curve which is described by a projectile: he infer. "red from observation the isochronism of the vibrations of a pen. "dulum, and the principle was soon after applied by Sanctorius "to the regulation of timekeepers. Stevinus, a Dutchman, was "the first that clearly stated the important law by which the equi. "librium of any three forces is determined: and the properties " of the centre of gravity were successively investigated by Lucas "Valerius, Lafaille, and Guldinus, who made some additions, to "the elegant propositions of Archimedes which relate to it." Should it be asked, which of the lectures of the second division seem to be written with more particular attention, an answer might be given in favour of the lectures on optics. Dr. Young seems to have bestowed peculiar labour on the study of that branch of natural philosophy: for one ma y easily discover new hints, new lights, and new explanations, in those optical lectures. In treating of the theories of optics, Dr. Young does not seem to give that satisfaction which the reader might be led to expect. But this defect, which could hardly be avoided in the lectures, is compensated by certain papers on that subject, which were first published in the philosophical transactions of the Royal Society, and which are reprinted in the second volume of the present work. The lectures on Sound may well claim the rank next to those on optics; yet some of them, and especially the thirtythird, which treats of harmonics, are rather in want of a more methodical arrangement, or a more detailed explanation. In their present state, they are not easily comprehended without repeated and attentive perusals; and of course could have been much less understood when delivered verbally. The twenty lectures of the last division, under the general title of Physics, embrace a variety of subjects, the most important of which are treated more at large, whilst others are explained in a more summary way, and some are little more than barely mentioned. After a general view of the first volume of the work, which is at present under consideration, it would be both useless and improper to enter into a particular examination, or to attempt to censure any part of it; for, since those lectures were compiled for the purpose of giving a superficial, yet extended, view of the modern state of philosophical knowledge, a severe examiner might easily find occasion to criticize the exceptionable part of almost every subject, that is mentioned in the course.-He might remark, that several propositions are destitute of demonstration; that a great many explanations are either too intricate, or not sufficiently illustrated by means of examples; he might call in question certain theories, and point out a variety of defective statements; which, however, seem intended to be as they are, for the purpose of avoiding minutiæ, that can hardly ever be remembered when heard in a lecture-room, or, if remembered, can seldom be of use to the hearer, who cannot possibly expect to become fully informed of a subject without farther study, or more particular application. It will, for instance, suffice for a lecturer to say, that a heavy body, dropped from a little altitude above the surface of the earth, will descend through 16 feet, in the first second of time, and this may be easily remembered. Yet such statement may be censured as being incorrect; for, the space abovementioned is a little longer than 16 feet. Its proper length, according to the nearest approximation of experimental investigation, being 16.087 feet; but the additional decimal fraction of 0.087 is neither easily remembered, nor, when remembered, is of any great importance to a superficial learner. The only question which might deserve discussion, is whether, in a course of lectures, it would be better thoroughly to explain and to illustrate the very first principles of a subject, without advancing a great way into it; or to give an enlarged, but superficial, view of every branch of the same. And though, at first sight, it may appear indifferent whether the one or the other of those plans be adopted; yet a slight consideration of the object for which the course of lectures is intended, will easily point out the plan to which the preference ought to be given.-Scientific lectures in general are delivered either to academies, colleges, and seminaries, of various kinds, in which, young persons are educated; or in towns, to a promiscuous company, of all ages and descriptions. The attendance of the former may be justly considered as professional students, who, being intended for the law, for physic, or for any other department, must be initiated into those branches of knowledge, which are more or less immediately subservient to their intended professions. And in this case |