ATWOOD, George, an author celebrated for the accuracy of his mathematical and mechanical investigations, and considered particularly happy in the clearness of his explanations, and the elegance of his experimental illustrations, was born in the early part of the year 1746. He was educated at Westminster school, where he was admitted in 1759. Six years afterwards he was elected off to Trinity College, Cambridge. He took his degree of bachelor of arts in 1769, with the rank of third wrangler; Dr Parkinson of Christ’s College being senior of the year. This distinction was amply sufficient to give him a claim to further advancement in his own college, on the list of which he stood the foremost of his contemporaries; and in due time he obtained a fellowship, and was afterwards one of the tutors of the college. He became master of arts in 1772, and in 1776 was elected a fellow of the Royal Society of London.

The higher branches of the mathematics had, at this period, been making some important advances at Cambridge, under the auspices of Dr Waring, and many of the younger members of the university became diligent labourers in this extensive field. Mr Atwood chose for his peculiar department the illustration of mechanical and experimental philosophy, by elementary investigations and ocular demonstrations of their fundamental truths. He delivered, for several successive years, a course of lectures in the observatory of Trinity College, which were very generally attended and greatly admired. In the year 1784 some circumstances occurred which made it desirable for him to discontinue his residence at Cambridge; and soon afterwards Mr Pitt, who had become acquainted with his merits by attending his lectures, bestowed on him a patent office, which required but little of his attendance, in order to have a claim on the employment of his mathematical abilities in a variety of financial calculations, to which he continued to devote a considerable portion of his time and attention throughout the remainder of his life.

The following, we believe, is a correct list of Mr Atwood’s publications:—1. A Description of Experiments to illustrate a Course of Lectures; about 1775 or 1776, 8vo. 2. This work was reprinted, with additions, under the title of An Analysis of a Course of Lectures on the Principles of Natural Philosophy. Cambridge, 1784, 8vo. 3. A General Theory for the Mensuration of the Angle subtended by two objects, of which one is observed by rays after two reflections from plane surfaces, and the other by rays coming directly to the spectator’s eye. Phil. Trans. 1781, p. 395. 4. A Treatise on the Rectilinear Motion and Rotation of Bodies, with a Description of Original Experiments relative to the subject. Cambridge, 1784, 8vo. 5. Investigations founded on the Theory of Motion for determining the Times of Vibration of Watch Balances. Phil. Trans. 1794, p∙ 119. 6. The Construction and Analysis of Geometrical Propositions, determining the positions assumed by homogeneal bodies, which float freely, and at rest, on a fluid’s surface; also determining the Stability of Ships, and of other Floating Bodies. Phil. Trans. 1796, p. 46. 7. A Disquisition on the Stability of Ships. Phil. Trans. 1798, p. 201. 8. A Review of the Statutes and Ordinances of Assize which have been established in England from the 4th year of King John, 1202, to the 37th of his present Majesty. Lond. 1801, 4to. 9. A Dissertation on the Construction and Properties of Arches. Lond. 1801,4to. 10. A Supplement to a Tract entitled a Treatise on the Construction and Properties of Arclies, published in the year 1801; and containing Propositions for determining the Weights of the several Sections which constitute an Arch, inferred from the Angles. Also containing a Demonstration of the Angles of the several Sections, when they are inferred from the Weights thereof. To which is added, a Description of Original Experiments to verify and illustrate the Principles in this Treatise. With occasional Remarks on the Construction of an Iron Bridge of one Arch, proposed to be erected over the river Thames at London. Part II. By the author of the first part. Lond. 1804,4to. Dated 24th November 1803. 11. A Treatise on Optics is mentioned by Nichols as having been partly printed by Bowyer in 1776, butnever completed.

It may be very truly asserted that several of these works of Mr Atwood have materially contributed to the progress of science, by multiplying the modes of illustration which experimental exhibitions afford for the assistance of the instructor; at the same time they can scarcely be said to have extended very considerably the bounds of human knowledge, or to have demonstrated that their author was possessed of any extraordinary talent or energy of mind in overcoming great difficulties or in inventing new methods of reasoning. The Analysis of a Course of Lectures has been little read; and it bears evident marks of having been composed before Mr Atwood had acquired a habit of accurate reasoning on physical subjects. In the first page, for example, the forces of cohesion and gravitation are completely confounded; and in the third we find the idea of perfect spheres touching each other in a greater or less number of points, notwithstanding the appearance of precision which the author attempts to maintain in his language.

The object of the paper on Pefiectiοη is, to illustrate and improve the construction of Hadley’s quadrant; and Mr Atwood proposes, for some particular purposes in practical astronomy, two new arrangements of the speculums, by which the rays are caused to move in different planes, and which he considers as affording greater accuracy for the measurement of small angles than the common form of the instrument, although not of general utility, nor very easily adjusted for observation.

The treatise on Pectilinear Motion and Potation exhi [7:4:188] bits a good compendium of the elementary doctrines of mathematical mechanics; but it shows a great deficiency in the knowledge of the higher refinements which had been introduced into that science by Daniel Bernoulli, and Euler, and Lagrange. The properties of simply accelerated and retarded motion are first discussed, and the phenomena of penetration experimentally examined; the laws of varying forces are then investigated, and the properties of the pendulum demonstrated; the vibrations of an elastic chord are calculated, “considering the whole mass to be concentrated in the middle point,” as an approximation; and then, instead of imitating and simplifying the elegant but complicated demonstrations of the continental mathematicians, the author most erroneously repeats, in the words of Dr Smith, the exploded doctrine, that “the string, during any instant of its vibration, will coincide with the harmonic curve.” The subject of a resistance, varying as the square of the velocity, is next examined; and some useful experiments on the descent of bodies in water are stated in confirmation of the theory. On this occasion, the author observes, with regard to the formation of the different strata of the earth, that bodies disposed to break into large masses, though specifically lighter, may easily have descended more rapidly through a fluid, than denser but more brittle bodies, so that the natural order of densities may thus have become inverted. He next examines the theory of rotation, and relates some very interesting experiments on rectilinear and rotatory motions; and he shows that Emerson and Desaguliers were totally mistaken in asserting that “the momentum produced is always equal to the momentum which produces it.” The last section of the work, which is devoted to the subject of free rotation, is the most elaborate of the whole; but it exhibits no material extension of the earlier investigations of the Bernoullis and Professor Vince; nor does it contain the important proposition of Segner, relating to the existence of three axes of permanent rotation, at right angles to each other, in every body, however irregular.

Notwithstanding these partial objections, the work may still, in many respects, be considered as classical. The paper on Watch-balances is principally intended to show the advantages which may be obtained, in Mr Mudge’s construction, from the effect of subsidiary springs in rendering the vibrations isochronous, their actions being limited to certain portions of the arc of motion. If the author has here again omitted to follow the continental mathematicians in some of their refinements of calculation, it must be confessed that his view of the subject has, in this instance, not only the advantages of simplicity, but also that of a nearer approach to the true practical state of the question, than is to be found in the more complicated determinations which had been the result of the labours of some of his predecessors.

. But, whatever may be the merits of these investigations, they appear to be far exceeded in importance by the papers on Ships, the first of which obtained for its author the honour of a Copleian medal. Its principal object is to show how much the stability of a ship will commonly vary, when her situation with respect to the horizon is materially altered; and how far the assumptions of theoretical writers, respecting many others of the forces concerned in naval architecture, will generally differ from the true state of these forces when they actually occur in seamanship. In the second part of the investigation, some errors of Bouguer and of Clairbois are pointed out; and the theoretical principles of stability are exemplified by a detailed calculation, adapted to the form and dimensions of a particular vessel, built for the service of the East India Company.

The latter years of our author’s life do not appear to have been productive of any material advantage to science. His application to his accustomed pursuits was unremitting, hut his health was gradually declining. He had no amusement except such as was afforded by the continued exercise of his mind, with a change of the object only; the laborious game of chess occupying, under the name of a recreation, the hours which he could spare from more productive exertions. He became paralytic some time before his death; and although he partially recovered his health, he did not live to complete his 62d year.

His researches concerning the history of the Assize of Bread must have required the employment of considerable diligence and some judgment in the discovery and selection of materials, although certainly the subject was not chosen for the purpose of affording a display of talent. His opinion respecting the operation of the assize, as favourable to the community, may by some be thought to be justified by the want of success which has hitherto attended the experiment on its suspension; but the advocates of that measure would certainly not admit the trial of a year to be sufficient for appreciating its utility.

The title-pages of the works on Arches explain the occasion on which they were brought forward, and at the same time exhibit a specimen of the want of order and precision which seems to have begun to prevail in the author’s faculties; while the works themselves betray a neglect of the fundamental principles of mechanics, which is inconceivable in a person who had once reasoned with considerable accuracy on mathematical subjects. An anonymous critic, who is supposed to have been the late Professor Robison (British Critic, vol. xxi. January 1804), very decidedly, and at the same time very respectfully, asserted Mr Atwood’s error in maintaining that there was no manner of necessity for the condition, that the general curve of equilibrium of an arch should pass through some part of every one of the joints by which it is divided; and in fact we may very easily be convinced of the truth of this principle, if we reflect that the curve of equilibrium is the true representative of the direction of all the forces acting upon each of the blocks, and that, if the whole pressure be anywhere directed to a point situated beyond the limit of the joint, there can be nothing whatever to prevent the rotation of the block on the end of the joint as a centre, until some new position of the block shall have altered the direction of the forces, or until the whole fabric be destroyed. The critic has also very truly remarked that the effects of friction have never been sufficiently considered in such arrangements; but a later author, in an anonymous publication, has removed a considerable part of this difficulty by showing that no other condition is required for determining these effects than that every joint should be perpendicular to the direction of the curve of equilibrium, either accurately or within the limit of a certain angle, which is constant for every substance of the same kind, and which he has termed the angle of repose. (l. l.)