run the risk, with the mob of gentlemen who write upon mechanics, of being thought as mad as if he were to have proposed reviving Bishop Wilkins’s notable plan for going to the North American colonies in a few hours, by rising in a balloon from the Earth and gently floating in the air until the Earth, in its diurnal rotation, have turned the desired quarter towards the suspended æronaut, whereupon as gently to descend; so necessary and wholesome is it occasionally to reconsider the apparently simplest and best established conclusions of science.” The following is from the _Scotsman_, which has always been distinguished for the accuracy of its scientific papers. The article bears the initials “C. M.,” which will at once be recognised as those of Mr. Charles Maclaren, for many years the accomplished editor of that journal:--“The beautiful experiment contrived by M. Foucault to demonstrate the rotation of the globe, has deservedly excited universal interest. * * * A desire has always been felt that some method could be devised of rendering this rotation palpable to the senses. Even the illustrious Laplace participated in this feeling and has left it on record. ‘Although,’ he says, ‘the rotation of the Earth is now established with all the certainty which the physical sciences require, still a direct proof of that phenomenon ought to interest both geometricians and astronomers.’ No man ever knew the laws of the planetary motions better than Laplace, and before penning such a sentence, it is probable that he had turned the subject in his mind, and without discovering any process by which the object could be attained; but it does not follow that if he had applied the whole force of his genius to the task, he would not have succeeded. Be this as it may, here we have the problem solved by a man not probably possessing a tithe of his science or talent; and, what is very remarkable, after the discovery was made, it was found to be legitimately deducible from mathematical principles. * * * In this, as in many other cases, the _fact_ comes first, and takes us by surprise; after which we find that we had long been in possession of the principles from which it flowed, and that, with the clue we had in our hands, theory should have revealed the fact to us long before. M. Foucault’s communication describing his experiments is in the _Comptes Rendus_ of the Academy of Sciences, for 3rd February, 1851. His first experiments were made with a pendulum only two metres (6ft. 6¹⁄₄in.) in length, consisting of a steel wire from ⁶⁄₁₀ths to ¹¹⁄₁₀ths of a millimetre in diameter (the millimetre is the 25th part of an inch); to the lower end of which was attached a polished brass ball, weighing 5 kilogrammes, or 11 English pounds. * * * A metallic point projecting below the ball, and so directed as if it formed a continuation of the suspension wire, served as an index to mark the change of position more precisely. The