MATHEMATICAL AND PHYSICAL SCIENCE. 



[Diss. VI. 



the former part of the statement ; and when we recol- 

 lect that the same period has given birth to the steam- 

 engine of Watt, with its application to shipping and 

 railways, to the gigantic telescopes of Herschel and 

 Lord Rosse, wonderful as works of art as well as in- 

 struments of sublime discovery, to the electric tele- 

 graph, and to the tubular bridge, we shall be ready 

 to grant the last part of the proposition, that science 

 and art have been more indissolubly united than at 

 any previous period. 



(6.) The Dissertation of Professor Playfair closes with 



Limits of the period of Newton ; that of Sir John Leslie, pro- 

 ^j? o ^ isser 'fessedly devoted to the history of the eighteenth cen- 

 tury, embraces some matters which belong more 

 properly to those which preceded and followed it. 

 After considering how I might best carry out the plan 

 of these essays, I have adopted the period from about 

 the year 1775 to 1850 as the general limit of my 

 review. We may imagine this period, of three quar- 

 ters of a century preceding the present time, to be 

 divided into three lesser intervals of 25 years each, 

 which have also some peculiar features of their own. 

 (7.) From 1775 to 1800 many branches of science still 



Character continued in the comparatively inert state which cha- 

 of the 18th racter i zed a g re at part of the eighteenth century, 

 century. There were, however, two or three notable excep- 

 tions. One was the continued successful solution of 

 the outstanding difficulties of the Theory of Gravity 

 applied to the moon and planets, a task in which the 

 continental mathematicians, and of these, in chief, 

 Lagrange and Laplace, had no rivals, or even coad- 

 jutors, on this side of the channel : Another was the 

 foundation of Sidereal Astronomy by Sir William 

 Herschel ; and the last was the commencement of a 

 system of Chemical Philosophy based on new and im- 

 portant experiments, and including the laws of heat 

 in combination with matter, which at that period very 

 naturally ranged themselves within the province of 

 the chemist. In this department two British and 

 one foreign name stand conspicuous, Black, Caven- 

 dish, and Lavoisier. I do not of course mean to affirm 

 that other branches of science were not cultivated 

 with success within the exact period of which we 

 speak. Electricity, for instance, first statical, after- 

 wards that of the pile, had a share in the discoveries 

 and speculations of the time. But these were rather 

 the mere extension of what had previously been thought 

 of; or the first dawn of future important results, whose 

 development fills a large space in the succeeding story. 

 Volta and his inventions belong rather to the nine- 

 teenth than to the eighteenth century. 

 (8.) The first quarter of the present century attained 



Character a higher and more universal celebrity. Scarcely a 

 period branch of physical science but received important 

 1800-1825. and even capital additions. Physical Astronomy in- 

 deed, no longer filled so large a space in the page of 

 discovery, simply because the exhaustive labours of 

 the geometers of the former period had brought it to 

 a stage of perfection nearly co-ordinate with the means 



of observation, and because, by the publication of the 

 Mecanique Celeste, Laplace had rendered available Mecanique 

 and precise the masses of scattered research accu- 

 mulated by the labours of a century since the close 

 of Newton's career of discovery. It was in some 

 sense a new book of " Principia," not, indeed, 

 the work of one, but of many ; nor of a few years, 

 but of two generations at least. Still there it was, 

 a great monument of successful toil, which, like its 

 prototype, was for many years to be studied, even by 

 minds of the highest order, rather than to be enlarged. 



But the other branches of Natural Philosophy (9.) 

 were now to make a stride, such as perhaps no pre- Experi- 

 ceding time had witnessed. The science of Optics 

 was speedily expanded almost twofold, both in its 

 facts and in its doctrines. Galvanic Electricity dis- 

 closed a series of phenomena not less brilliant and 

 unexpected in themselves than important from the new 

 light they threw on the still dawning science of che- 

 mistry, and from the power of the tool which they 

 placed in the hands of philosophers. Before the 

 first quarter of the present century closed, the import- 

 ant and long suspected connection between Electricity 

 and Magnetism was revealed, and its immediate con- 

 sequences had been traced out with* almost unpa- 

 ralleled ingenuity and expedition. The basis of the 

 science of Radiant Heat, slightly anticipated by the 

 philosophers of the eighteenth and even the seven- 

 teenth centuries (Lambert and Mariotte), was finally 

 laid in a distinct form, assigning to the agent, heat, 

 an independent position dissociated from grosser 

 matter, such as light had long enjoyed. Astronomy, 

 though enriched on the very first night of the new 

 century by the discovery of a small planet, the he- 

 rald of so many more of the same class, made per- 

 haps less signal progress ; but Chemistry, besides the 

 aid it received from the invention of the pile, had a 

 triumph peculiarly its own in the addition of the 

 comprehensive doctrine of Definite Proportions, des- 

 tined to throw at some later time a steady light on 

 the vexed question of the constitution of matter. 

 The great number of scientific names of the first or- 

 der of merit concerned in these numerous discoveries 

 marks the extraordinary fertility of the period. They 

 are imperfectly comprehended in the following list : 

 Young, Malus, Sir David Brewster, Fresnel, and 

 Arago ; Volta, Dalton, Davy, and Oersted ; Prevost, 

 Leslie, and Fourier ; Gauss, Ivory, Olbers, Bessel, 

 and Encke. 



Of the twenty-five years just elapsed, it is not so (10.) 

 easy to speak with precision. The voice of criticism 

 may be fairly uttered with that reserve which every 

 one must feel in speaking of his immediate contem- 

 poraries. Yet it may perhaps be stated without 

 just cause either of offence or regret, that it has not 

 on the whole been characterized by the full maturity 

 of so many commanding minds. Of the great dis- 

 coverers of the former period, several survived and 

 continued their efficient labours during no small por- 



