Sept. 6. 1851.] 



NOTES AND QUERIES. 



177 



3L\cjpltc^. 



PENDULUM DEMONSTRATION OF TUE EARTh's 

 ROTATION. 



(Vol. iv., p. 129.) 



I beg to send you a few remarks on the note of 

 A. E. B., concerning the "Pendulum Demon- 

 stration of the Earth's Rotation." 



Your corresi)ondent ajjpears to consider that 

 the only fact asserted by the propounders of the 

 theory, is a variation in the plane of oscillation, 

 caused by " the difference of rotation due to the 

 e.\cess of velocity witli which one extremity of the 

 line of oscillation may be affected more than the 

 other ; " the probable existence of which he proves 

 by imagining a pendulum suspended over a point 

 half-way between London and Edinburgh, and 

 set in motion by being drawn towards and re- 

 tained over London, and thence dismissed on its 

 course. It is clear that in such a case the pen- 

 dulum would at starting be impressed with the 

 same velocity of motion in an eastern direction 

 whicii tlie retaining power in London had, and 

 that its i)ath would be the result of this force com- 

 pounded with that given by gravity in its line of 

 8US|)eiisi()n, i.e. towards the north, and its course 

 would therefore be one subject to easy calculation. 

 I shouhl imagine that this disturbing force arising 

 from the excess of eastern velocity possessed by 

 the starting point over that of suspension, would 

 be inappreciable after a few oscillations; but at 

 all events it is evident that it might readily be 

 avoideil by setting the pendulum in motion by an 

 impulse given beneath the point of suspension, by 



Brunswick Mum. — Why was the beer called 

 Brunswick Mum so named ? When I was young 

 it used to be drunk in this country, and was, I 

 am told, extensively exported to India, &c. Is it 

 still manufactured ? G. Creed. 



[Skinner calls Mum a strong kind of beer, introduced 

 b}- us from Brunswick, and derived either from 

 German 7nuinmeln, to mumble, or from tnum (silentii ! 

 index), i.e. either drink that will (iit nos dicimus) 

 make a cat speak, or drink that will take away the 

 power of speech. 

 " The clamorous crowd is hush'd with mugs of mum, 



Till all, tun'd equal, send a general hum." — Pope. 



Brunswick Mum is now advertised for sale by many 

 publicans in the metropolis.] 



Cleaning of " Rasher." — What is the derivation 

 of the word rasher, " a rasher of bacon ? " 



J. II. C. 



Adelaide, South Australia. 



[Surely from the French raser, to shave — a shaving 

 of bacon. Our correspondent will probably recollect 

 that vessels that have been cut down are commonly 

 known as razees.^ 



giving to it a direction east and west as suggested 

 by A.E. B, or by several other expedients which 

 must occur to a mathematician. 



Your coiTespondent proceeds by requiring that 

 there should be shown "reasonable ground to in- 

 duce the belief that the ball is really free from the 

 attraction of each successive point of the earth's 

 surface," and is not as " effectually a partaker in 

 the rotation of any given point" as if it were fi.xed 

 there; or that "the duration of residence" ne- 

 cessary to cause such effect should be stated. 

 Now I certainly am aware of no force by which a 

 body unconnected with the earth would have any 

 tendency to rotate with it ; gravity can only act 

 in a direct line from the body affected to the 

 centre of the attracting body, and the motion in 

 the direction of the earth's rotation can only be 

 gained by contact or connexion, however mo- 

 mentary, with it. The onus of proving the ex- 

 istence of such a force as A. E. B. alludes to, must 

 surely rest with him, not that of disproving it with 

 me. What the propounders of this theory claim 

 to show is, I humbly conceive, this, — that the 

 direction in which a pendulum oscillates is co?istan^, 

 and not affected by the rotation of the earth be- 

 neath it : that as when suspended above the pole 

 (where the point of suspension would remain 

 fixed) the plane of each oscillation would make a 

 different angle with any given meridian of lon- 

 gitude, returning to its original angle when the 

 diurnal rotation of the earth was completed ; and 

 as when suspended above the equator, where the 

 point of suspension would be moved in a right 

 line, or, to define more accurately, where the plane 

 made by the motioii of a line joining the point of 

 suspension and the point directly under it (over 

 which the ball would remain if at rest) would be 

 a fiat or right plane, the angle made by each suc- 

 cessive oscillation with any one meridian would be 

 the same, so, at all the intermediate stations be- 

 tween the pole and the equator, where the point 

 of suspension would move in a line, commencing 

 near the pole with an infinitely small curve, and 

 ending near the equator with one infinitely large 

 («'. e. where the plane as described above would be 

 thus curved), the angle of the plane of oscillation 

 with a given meridian would, at each station, vary 

 in a ratio diminishing from the variation at the 

 pole until it became extinct at the equator, whic;h 

 variation they believe to be capable both of ma- 

 thematical proof and of ocular demonstration. 



I do not profess to be one of tlie proj)Ounders of 

 this theory, and it is very probable that you may 

 have received from some other source a more 

 lucid, and perhaps a more correct, explanation of 

 it ; but in erase you have not done so, I send you 

 the foregoing rough "Note" of what are my 

 opinions of it. E. II. Y. 



