FORBES.

forced to abandon his house, and take refuge in the island of Skye, where he remained till after the battle of Culloden. On his return, in place of reaping the fruits of his services, he was regarded with jealousy and aversion by the government. Even the large sums of money which he had advanced were never repaid him; and it is said that the ingratitude of the government, coupled with the perfidy of many of his friends and neighbours, who had changed sides more than once during this miserable affair, weighed so heavily on his spirits as to shorten his life. He discharged his judicial duties, however, with great zeal and ability till within a month of his death, which took place on December 10, 1747. There is a beautiful portrait of the Lord President F., who was a man of great elegance of person and manner, in the Parliament House in Edinburgh. The most recent and complete biography of Forbes is that of Mr Burton in his Lives of Simon Lord Lovat and Duncan Forbes, 1848.

not one shilling of which was ever repaid him. But on this, as on all other occasions, Duncan's partisanship was of the most moderate kind. After the suppression of the rebellion, he was opposed to the project of carrying the prisoners out of Scotland, to be tried by English juries, and he wrote to Lord Islay, when he heard that it was proposed to appoint him lord advocate, that he should certainly decline that office. He wrote to his brother, proposing a subscription for the comfort of the prisoners. It is certainly Christian,' he said, and by no means disloyal, to sustain them in their indigent state till they are found guilty.' To the forfeitures also he was opposed, on grounds of policy as well as of humanity. The only effect of his moderation was to bring suspicion on his own loyalty. But he was too important for his promotion to be arrested. In 1716, he was appointed depute to the lord advocate; in 1722, he was returned to sit in parliament for the Inverness district of burghs; and in 1725, he was lord advocate. He was not distinguished as a debater, but he was largely employed at this FORBES, EDWARD, an eminent naturalist, was period of his career in appeal cases, and he enjoyed born at Douglas, Isle of Man, February 12, 1815, the friendship of Sir Robert Walpole, Lyttleton, and died in Edinburgh, November 18, 1854. He Mansfield, and Hardwick. He seems even to have received a desultory and imperfect education in penetrated the literary circles in which Swift, Pope, early life, in consequence of ill health; but when and Arbuthnot were the ruling stars. In 1734, his he left home at the age of 16, he had already brother John-Bumper John, as he was called-possessed himself of a very considerable amount of died, and he succeeded to the estates of the family, knowledge in the departments of botany, zoology, In earlier life, Duncan partook of the convivial and geology. In 1831, F. went to London, with habits for which his family was distinguished, in an the intention of becoming a student at the Royal age that was famous for deep potations. Mr Burton Academy; but although he evinced much readiness records various anecdotes illustrative of his powers in drawing, his artistic talents were not sufficiently in this direction, but he abandoned the practice marked to hold out any prospect of success in the when his health began to suffer, and devoted him- event of his making art his profession; and he thereself to more serious if not more onerous duties. fore determined to turn his attention to medicine, During many subsequent years, he in no insig- and, with this view, entered the university of Edin nificant degree ruled the destinies, and contri-burgh. In 1836, he finally relinquished his special buted to the dawning prosperity of Scotland by medical studies, to devote himself exclusively to fostering and developing her internal resources. the natural sciences. In 1836-1837, he attended His policy was to extinguish the rebellion by gaining lectures at Paris, where he studied under Geoffroy over the Jacobites to the government. The purity St Hilaire, Jussieu, and De Blainville, while he at and uprightness of F.'s character were subjected to a the same time availed himself with diligence of all severe test. His whole correspondence during these the advantages afforded to students by the museums troubled times came to light some seventy years and libraries of Paris. From the first year of his after his death; and though few men ever wrote or college life, F. had spent his summer vacations were written to with less idea of publication, we in rambles over various parts of Great Britain, or have not,' says Mr Chambers (Biographical Dic- in excursions on the continent, and the results of tionary of Eminent Scotsmen), to detect a single the observations which he made during these tours, one of his advices or proceedings, by the exposure which were published by him either in the form of of which even a private gentleman of the most separate works, or in the pages of current scientific delicate honour, and the most reasonable views, journals, sufficiently attest his diligence as an would have cause to feel a moment's uneasiness.' observer, and his exact appreciation of analogies Having freed himself from the shackles of party, and differences of forms. F. may almost be regarded his great object was to improve the trade and as the originator of the use of the dredge, which he agriculture of the kingdom. But his views of employed with equal success in investigating the political economy were not greatly in advance of marine fauna of our own seas, and of the Mediterhis time; for in order to encourage the use of malt, ranean and the Ægean. In 1841, he joined the surhe presented to the government a long and detailed veying ship Beacon, as naturalist, and accompanied scheme for preventing, or rather for punishing the that vessel during the survey of a part of Asia Minor, F. was appointed President of the and co-operated in the exploration of many of the Court of Session in 1737; but he still continued his Xanthian cities. On his return to England in 1843, interest in the general improvement of the country. he found that he had, during his absence, been Though he was aware of the character, and, in elected to the chair of botany, King's College, general, of the designs of the Jacobites, the rebel- London. He was soon afterwards named curator lion of 1745 took the President by surprise. But of the Geological Society; and from that period till he was no sooner aware of the danger than he has his removal to Edinburgh, he remained in London, tened to the north, as he had done on the occasion living in a vortex of scientific labours and literary of the former outbreak, and by his presence and the work. In 1844, he was appointed paleontologist influence which he possessed in his own district, to the Museum of Geology in connection with the did much to counteract the proceedings of the Ordnance Geological Survey; and in 1851, on the rebels. Lovat, as is well known, betrayed both opening of the new buildings in Jermyn Street, him and the government, and actually made an London, he was named professor of natural history attack on Culloden House, from which he was in the School of Mines. In 1852, he was chosen beaten off with great spirit by the President and president of the Geological Society, an honour never his people. When the rebellion spread, he was before conferred on so young a man; and in 1853,

use of tea.

FORBES.

on the death of Professor Jameson, he was elected to the vacant chair of Natural History in the university of Edinburgh. In the summer of 1854, he delivered a short course of lectures-the only one he was destined to give for at the commencement of the winter session he was seized with a severe illness, which speedily proved fatal, and terminated his life in the 39th year of his age, in the very zenith of his fame, and in the full vigour of his intellectual powers. F. had been a voluminous writer and a diligent observer of nature from his earliest youth, and had collected an immense mass of materials, many of which were, however, left at his death in a disorganised condition. He did much to advance and systematise special departments of natural history, both by his own labours and by the stimulus which he imparted to his associates and pupils; and it would be difficult to instance any naturalist who has exercised a greater influence on the thought and line of inquiry pursued by those who have cultivated the same branches of knowledge. His classification of the British Star-fishes opened a new era in that branch of zoology; and his discovery that air-breathing molluscs lived at the period of the Purbeck beds, has been the means of rectifying many erroneous hypotheses, and throwing unexpected light on several hitherto obscure points of geology, while the inferences which he drew from the presence of those animals have been fully corroborated. His Report on the Egean Sea, and his observations of the tertiaries of Cos, which have proved of great value to geology, raised him to the highest rank among living naturalists. From an early period, he had directed his attention to the distribution of animal and vegetable life in different zones of the sea and land, and his observations in this path of inquiry have opened many new fields of research. F. was a diligent contributor to the current scientific literature of the day, and many of his best papers were written for the meetings of the British Association, of which an active member, and for the various societies with which he was connected; while he also took a most efficient share in the labours of the Ordnance Survey during his connection with its staff. His separate works, papers, and monographs, of which upwards of 200 are published, and many of which are copiously illustrated by his own beautiful drawings, cannot be individually specified; but among them we may instance the following: On the Distrib. of Pulmonif. Mollusca in Europe (1838); Malacol. Monensis (1838); Star Fishes (1841); The Radiata and Mollusca of the Egean (1843); Travels in Lycia (written in conjunction with Lieutenant Spratt, 1846); Nakedeyed Medusa (1847); British Mollusca (1853, 4 vols. 8vo, conjointly with S. Hanley); the Map of Homoiozoic Belts (Johnston's Phys. Atlas, 1854); Collection of Literary Papers by E. Forbes (1855); &c. See Memoir by G. Wilson and A. Geikie, 1861. FORBES, SIR WILLIAM, of Pitsligo, Bart., an eminent Scottish banker, son of Sir William Forbes, Bart., advocate, was born in Edinburgh, April 5, 1739. He succeeded his father when only four years old, and received his education at Aberdeen. In his 15th year, he was introduced into the bank at Edinburgh of Messrs John Coutts & Co.; and in 1761, was admitted a partner. In 1763, one of the brothers Coutts having died, while another retired on account of ill health, and two others were settled as bankers in London, a new company was formed, consisting of Sir William Forbes; Mr Hunter, afterwards Sir James Hunter Blair; Mr, afterwards Sir Robert Herries; and Messrs Stephen and Cochrane. They at first carried on business in the name of the old firm. On 1st January 1773,

he was

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however, on some changes in the partnership taking place, the name was changed to that of Sir W. Forbes, J. Hunter, & Co., and of this firm Sir William continued to be the head till his death. In 1781, he purchased the estate of Pitsligo, Aberdeenshire, which had been forfeited by Lord Forbes of Pitsligo for taking part in the rebellion of 1745. Animated by genuine patriotism and public spirit, he introduced the most extensive improvements on it, and laid out and built the village of New Pitsligo. He was a member, with Johnson, Burke, Garrick, Reynolds, and others, of the celebrated Literary Club of London, and the author of a Life of his friend, Dr Beattie, the poet, published, with his works, in 2 vols. 4to, in 1805; also of Memoirs of a Banking House, being the history of his own, edited by Mr Robert Chambers (Edinburgh, 1860). He died at his seat near Edinburgh, November 12, 1806, aged 68. By his wife, Elizabeth, eldest daughter of Sir James Hay of Hayston, Bart., he had three sons and five daughters. Universally esteemed and respected, his character is well described by Sir Walter Scott in the introductory address of one of the cantos of Marmion. His bank became, in 1830, the Union Bank of Scotland.

FORBES, JAMES DAVID, Principal of the United College in the university of St Andrews, a grandson of Sir W. Forbes, the banker, was born at Colinton, near Edinburgh, April 20, 1809. He studied in the university of Edinburgh from 1825 until 1830, when he was admitted to the Scottish bar. On the death of Sir John Leslie (q. v.), he was appointed, in 1833, to the chair of natural philosophy in the university of Edinburgh, after a contest in which, among other competitors, he was opposed by Dr (afterwards Sir David) Brewster and Mr Galloway. In 1842, the Institute of France enrolled him among its corresponding members. He is, besides, a member of numerous other scientific societies at home and abroad, has received the Royal and the Rumford medals from the Royal Society of London, and two Keith medals from the Royal Society of Edinburgh, and is D.C.L. of Oxford. In 1860, F. resigned his chair in Edinburgh, to become Principal of the United College in the university of St Andrews. Among his contributions to science are-the polarisation of radiant heat by the tourmaline, and also by reflection (1836), and its circular polarisationdiscoveries forming some of the strongest proofs of the identity of calorific and luminous rays; the unequal polarisation of heat from different sources (1844); the refrangibility of heat; the depolarisation of heat; &c. This whole series of experimental results is of a very high order of importance. He is, however, best known to the world in general by his researches on the motion of glaciers. See Travels in the Alps (1843); Norway and its Glaciers (1853); Tour of Mont Blanc and Monte Rosa (1855); and Occasional Papers on the Theory of Glaciers (1859). He was undoubtedly the first to establish the great fact, that glacier ice moves in its channel like a viscous fluid, the middle moving faster than the sides, and the upper portions faster than the lower. His theory of glacier phenomena has encountered a good deal of opposition from some quarters, and cannot yet be considered as settled. See GLACIERS. In meteorology, F. has, among other things, improved Wollaston's application of the thermometer to the determination of heights, and has verified with great care Fourier's theoretical results concerning the temperature of the ground at different depths and in different kinds of soil and rock. Besides the works already named, numerous very valuable papers by F. are to be found in the Transactions of the Royal Societies of London and

417

FORBES-FORBES MACKENZIE ACT.

Edinburgh, in the Edinburgh Philosophical Journal, 1, to inn or hotel keepers; 2, to public-house keepers; and other periodicals.

FORBIDDEN FRUIT-FORCE; ENERGY.

FORCE; ENERGY.

two, and depend merely on the distance between in popular language, an imponderable. The almost them, then we can express the required proposition universal opinion of physicists, however, seems to in the following form:

Any change of vis-viva in the system corresponds to an equal amount of work gained or lost by the attractions of the particles on each other.

be, that even the former must be accounted for in some such way. Newton, in his second letter to Bentley, says, with respect to gravitation (and it is obvious that similar language is applicable to molecular forces generally): You sometimes speak of gravity as essential and inherent to matter. Pray, do not ascribe that notion to me, for the cause of gravity is what I do not pretend to know.' And again in the third letter: 'It is inconceivable that inanimate brute matter should, without the mediation of something else, which is not material, operate on, and affect other matter without mutual contact, as it must do, if gravitation, in the sense of Epicurus, be essential and inherent in it; and this is one reason why I desired you would not ascribe innate gravity to me. That gravity should be innate, inherent, and essential to matter, so that one body may act upon another at a distance through a vacuum, without the mediation of anything else, by, and through which their action and force may be conveyed from one to another, is to me so great an absurdity, that I believe no man who has in philosophical matters a competent faculty of thinking, can ever fall into it. Gravity must be caused by an agent acting constantly according to certain laws; but whether this agent be material or immaterial, I have left to the consideration of my readers.' Of what that medium may consist, we cannot, of course, hazard even a conjecture; but if it be composed of separate atoms

What is spent, then, in work, is stored up in visviva; and conversely, the system, by losing some of its vis-viva, will recover so much work-producing power. If we call the former, as is now generally done, Actual, and the latter Potential, Energy, we may express the above by saying, that in any system of bodies where the before-mentioned restrictions are complied with, the sum of the actual and potential energies cannot be altered by the mutual action of the bodies. The most simple and evident illustrations of this proposition are to be found in the case of the force known as gravitation. The potential energy of a mass on the earth's surface is zero, because, not being able to descend, it has, in common language, no work-producing power. If it be raised above the surface, and then dropped, it is easy to see that the work expended in raising it will be exactly recovered as vis-viva after its fall. For (see FALLING BODIES) a mass falling through a space, h, to the earth acquires a velocity v, such that v2 = 2gh, mv2 or if m be the mass, mg.h. The left-hand side gives the vis-viva acquired by the fall-the right is the product of the weight (mg) and the height fallen through- or is the work required to elevate the mass to its original altitude. Hence we may calculate the amount of work-i. e., not continuous-it is evident that a second which can be obtained from a head of water in driving water-wheels, &c., remembering, however, that there is always a loss (as it is usually called) due to friction, &c., in the machinery. That there is a loss in useful power, is true, but we shall find presently that in energy there is none, as indeed our general result has already shewn. Where the apparently lost energy goes, is another question.

2

=

Another good example of potential energy is that of the weights in an ordinary clock. It is the gradual conversion of potential into actual energy in the driving weight which maintains the motion of the clock, in spite of friction, resistance of the air, &c.; and we have in the actual energy of sound (which is motion) a considerable portion of the expended potential energy of the striking weight. A coiled watch-spring, a drawn bow, the charged receiver of an air-gun, are good examples of stores of potential energy, which can be directly used for mechanical purposes.

The chemical arrangement of the different components of gunpowder, or gun-cotton, is such as corresponds to enormous potential energy, which a single spark converts into the equivalent active amount. But here, heat has a considerable share in the effects produced; it may then be as well, before proceeding further, to consider how we can take account of it, and other physical forces, as forms of energy.

medium will be required to help the particles of the first to act on each other (for without this, the first medium would be merely obstructive), and so on. This must stop somewhere; why not, then, at the first? But in the present state of our knowledge of mechanics, a continuous medium is barely conceivable, and its motions, &c., present considerable difficulties to even plausible mathematical treatment. If we take the view opposed to Newton's, as Mosotti and others have done (their ideas are considered further on), we can, in a very artificial manner, however, account for gravitation and molecular action; but, as before said, the foundations of this attempt at explanation are hardly tenable.

Just as sound depends on the elasticity of the air and vibrations thereby maintained and propagated, light and radiant heat, which are certainly identical, most probably consist in the vibrations of some very elastic fluid. This has been provisionally named Ether (q. v.). If it be continuous, it may help us to account for the first two categories of force also, as we have already seen; if not so, as is more likely, fresh difficulties arise. Light and heat, however, are undoubtedly forms of motion, and correspond, therefore, to so much vis-viva or actual energy. Even heat in a liquid or solid body must correspond to some vis-viva in the material particles, since a hot body can give out both light and heat, and a body may be heated by luminous or calorific rays which are vibratory, as we have seen.

Correlation of Physical Forces.-So far as we yet know, the physical forces may be thus classified: I. GRAVITATION (q. v.); II. MOLECULAR FORCES — Class IV. contains perhaps the most puzzling of COHESION (including CAPILLARITY), ELASTICITY, all these forces. That there is something in comCHEMICAL AFFINITY; III. HEAT AND LIGHT; IV. mon in all the forms of electricity, and that magELECTRICITY (including MAGNETISM); V. ANIMAL netism is nearly related to them, is certain; it is FORCE; VI. VITAL FORCE, having, as some most probable, also, that frictional electricity, when statirrationally suppose, an analogue in inorganic masses, ical, consists in something analogous to a coiled which may be called Crystalline Force. (This idea spring, or is a form of potential energy-the others is examined further on.) Of these, I., II., and some being forms of actual energy. Some have supposed forms of III., are more immediately connected with magnetism to be also a form of potential energy, matter than the others-that is to say, that the but Ampère's discoveries have materially lessened remainder almost necessitate the hypothesis of the the probability of the truth of this hypothesis. We existence of some medium unlike ordinary matter, or, | shall consider this again.