EEVIEWS — MATHEMATICAL AND PHYSICAL SCIENCE. 369 



preceding the present time, to be divided into three lesser intervals of 25 years 

 each, which have also some peculiar features of their own. 



From 1775 to 1800, many branches of science still continued in the compara- 

 tively inert state which characterised a great part of the eighteenth century. 

 There were, however, two or three notable exceptions. One was the continued 

 successful solution of the outstanding difficulties of the theory of gravity applied 

 to the moon and planets, a task iu which the continental mathematicians had no 

 rivals or even coadjutors on this side of the channel ; another was the foundation 

 of sidereal astronomy ; and the last was the commencement of a system of chemi- 

 cal philosophy based on new and important 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. 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, afterwards that 

 of the pile, had a share in the discoveries and speculations of the time. But these 

 were rather the extension of what had been previously thought of, or the first 

 dawn of future important results, whose development fills a large space in the 



succeeding story 



The first quarter of the present century attained a higher and more universal 

 celebrity. Scarcely a branch of physical science but received important and even 

 capital additions. Physical astronomy indeed no longer filled so large a space in 

 the page of discovery, simply because the exhaustive labors 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 and precise the masses of scattered research ac- 

 cumulated by the labors of a century since the close of Newton's career of dis- 

 covery. 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 blanches of natural philosophy were now to make a stride, such 

 as perhaps no preceding time had witnessed. The science of optics was speedily 

 expanded almost two-fold, both in its facts and in its doctrines. Galvanic elec- 

 tricity disclosed a series of phenomena not less brilliant and unexpected in them- 

 selves, than important from the new light thus thrown on the still dawning science 

 of chemistry, 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 impor- 

 tant and long-suspected connection between electricity and magnetism was re- 

 vealed, and its immediate consequences had been traced out with almost unparal- 

 lelled ingenuity and expedition. The basis of the science of radiant heat, slightly 

 anticipated by the philosophers of the eighteenth aud even the seventeenth cen- 

 turies, was finally laid in a distinct form, assigning to the agent, heat, an indepen- 

 dent 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 herald of so many more of the same class, made 

 perhaps 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 com- 

 prehensive doctrine of definite-proportions, destined to throw at some later time a 

 VOL. II. — Z 



