those results have been denied, and an experimentum crucis attempted by the author of this volume, which appears to prove the existence of two distinct species or modes of transmitting heat, produced, at one and the same time, from luminous hot bodies. The attempt of Berard to prove that simple heat is subject to polarisation, like light, has failed, on being repeated by the author and by Professor Lloyd. Very recently some important results have been obtained by sir D. Brewster, and still more singular facts have been made known by MM. Nobili and Melloni, by means of a thermo-multiplier of the most extreme sensibility.

But it would be endless to dilate upon the mere titles of researches of which we can give no satisfactory history; and we are unable to do more, before concluding, than very briefly to refer to the general condition of the means we enjoy for prosecuting physical research.

The great increase of institutions and societies established for the purpose of promoting, in various ways, the prosecution of science and the diffusion of philosophical information, during the eighteenth and present centuries, has been a striking feature, equally demonIstrative of the extended diffusion of a taste for such pursuits, and efficacious towards its further progress. The societies of Berlin, Turin, and Petersburgh, besides numerous others of scarcely inferior reputation on the Continent, and those of Edinburgh, Dublin, and Cam.. bridge in our own country, have been the worthy offspring of the great parent institutions of a preceding century. The regular publication of their transactions, besides the appearance of a number of periodical journals, expressly devoted to the purposes of physical science, has exercised a most powerful sway over the scientific taste of the age in every way most beneficial to the cultivation of these branches of knowledge. Nor must we omit to mention the extraordinary impulse given to these pursuits by the annual meetings of the continental philosophers and naturalists; nor the still more effectual aid afforded to the same great objects in our own country

by the British Association for the Promotion of Science, whose several past anniversaries hold out the most encouraging prospects of future utility; and which, by the judicious measure of drawing up reports on the present state of our knowledge of each branch of science; and recommending subjects for investigation, as well as by the concentration to one focus of all the intellectual power which can be thrown on the several subjects, and the promotion of fair and friendly discussion, instead of prolonged and irritating paper-war on any disputed points (not to dwell upon the more general and obvious benefits), may be said to have done already for the science of the country more than any other institution within the same time.

Conclusion.

In drawing to the conclusion of such a survey as we have attempted of the progress of physical knowledge, a host of reflections of the most interesting description naturally crowd upon the mind. We had hoped to have wound up a far more complete history, by entering freely upon some discussion of the advantages attending the prosecution of science, of the evils sometimes sup.posed to be involved in it, of its effects, though cultivated only by a few, indirectly experienced by society at large; its connection with physical and still more with moral civilisation; its existing condition and future prospects, in our own and other countries; the influence of various national institutions, whether in promoting or repressing its progress; the state of public opinion respecting its claims; the recognition of scientific instruction as a branch of education. But the consideration of these and many other kindred topics of the highest interest we are compelled to abandon, from the pressing necessity imposed on us by the limits of our volume. There are also many topics commenced in previous parts of our sketch, to which a continuation is

manifestly wanting, but which we are thus precluded from supplying.

There is one consideration which alone affords us any satisfaction for the unforeseen deficiency under which this portion of our history labours, - the circumstance that all these topics are, in fact, embodied in the different treatises of the Cabinet Cyclopædia upon the several branches of physical science. To enumerate and explain the series of recent discoveries by which those sciences have been brought to their existing state of completeness, would be little else than to engage in systematic descriptions of the entire sciences. And when we have traced the progress by which the first principles of philosophic truth were originally fixed, and the first great advances made in the developement of the laws of the material world, the discussion of the successive improvements upon those principles would be little different from the actual exposition of the facts and theories whose aggregate constitutes the systematic scheme of the different departments. To these several treatises, then, we must be content to refer our readers to collect the recent history of scientific discovery.

INDEX.