20 Mr. A. Day on the Rotation of the Pendulum, 



is expressed, the same fraction, — -^, occurring in both. But 



this explanation is accompanied, or rather prefaced, by some 

 remarks, which represent the problem, first, as having excited 

 much more attention than it deserved ; next, that the rotation 

 of the pendulum is not an immediate effect of the earth's rota- 

 tion ; and thirdly, that the rotation of the pendulum is only an 

 apparent rotation. Now on this I cannot help remarking, that 

 the problem would have been most interesting, and deserving 

 all the scientific examination it received, if only as a purely spe- 

 culative or abstract one ; and it was very remarkable that the 

 precise case had never been discussed. As it was, it took mathe- 

 maticians by surprise, baffled not a few respectable professors of 

 the science, and was wrongly apprehended by several analysts of 

 considerable eminence. None of the analytical solutions, if 

 such they can be termed, that have from time to time appeared 

 in this country, have established anything more than is done 

 with far greater clearness and simplicity by the explanation 

 given in the work referred to ; and the whole thing, notwith- 

 standing its great interest and novelty, has sunk into temporary 

 contempt and neglect, as if the scientific republic was rather 

 ashamed of having allowed so much discussion and so much 

 algebra to be wasted on a thing so readily demonstrable by a 

 person tolerably conversant with Euclid only, or, to say the least, 

 with Euclid and the first elements of plane trigonometry. By 

 way of retaliation, as there is no glory to be got out of it, the 

 problem is now never mentioned, and a large body of people at 

 this moment look upon the whole thing as tacitly given up, not- 

 withstanding that the exact experiments of Mr. Bunt, certainly 

 undertaken with no bias in favour of bringing out the precise 

 result, have proved it, in a great variety of trials, to be true in 

 practice, which is by no means necessary to establish the truth 

 of the theoretic reasoning. It is not however as a speculative 

 case that the problem is of the highest interest, but as an imme- 

 diate proof of the earth's motion round its axis ; and the dis- 

 covery was hailed as important chiefly on this ground by the 

 members of the French Institute. It is true you do not see the 

 earth's rotation any more than before, nor does the pendulum 

 move away at a rate necessarily corresponding with that in which 

 the former is performed. I may state the real value of the 

 illustration thus. It is only within a comparatively recent period 

 of the world's history that the apparent motion of the heavens 

 has been finally reconciled with the supposition of a motion in 

 the spectator on the earth's surface, and not in them ; and while 

 no objection can be raised against the adequacy of this suppo- 

 sition to account for what is witnessed, there are a hundred 



