1918] on The Spinning-Top in Harness 293 



over the wheels, as hiirh as it can go under the old cramping limita- 

 tion of the loading- gauge of bridge and tunnel. 



A literary friend in the audience has called my attention to 

 de Quincey's account of a wonderful brother who claimed the power 

 of rising against gravity, to walk like a fly on the ceiling, provided 

 with spin enough, but that he would require the flagellation of a 

 whip-top in harness, emblem of fortitude in adversity. " Tu ne cede 

 malis, sed contra audentior ito." And here, too, we may find an 

 explanation of the simile in the epigram of Callimachus, advice 

 against marrying a rich wife. 



Without attaining so far as the positive levity of de Quincey's 

 brother, we have seen how a top can be made to climb a pole, in the 

 model described to the Royal Society in their Proceedings here by 

 Mr. Tournay Hinde. And Mr. Brennan can make it run along the 

 tight rope or on a single rail, concealed in harness inside a carriage, 

 to which it gives the upright stability, acting as automatically as the 

 brain in riding a bicycle. 



In the description of the American poet — 



" Are you the Mr. Brennan makes gyroscopic tops 

 To keep a car in balance when it runs or if it stops 

 On single rail or wire rope that's stretched across a chasm? 

 Pray write and tell me, Mr, Brennan, if you're the man that has 'em." 



Axial stability of motion of an elongated body through the air, 

 an arrow, bullet, or shell, is maintained by the gyroscopic action of 

 the spin imparted by the rifling ; and the calculation of the least 

 amount required is a delicate question of dynamics. No more spin 

 should be given than absolutely necessary, or the shell or bullet will 

 be uneasy in flight, as a ship is uneasy among waves if bottom-heavy, 

 as recommended by Euler, the weights stowed too low. 



Passing from small to large applications, the Parsons turbine in 

 the steamship requires to be treated on gyroscopic theory for motion 

 among the waves. Rolling does not affect them, but the internal 

 stress due to pitching becomes important, and must receive investiga- 

 tion. So, too, if electric dynamos are mounted with axle across the 

 ship, they are very sensitive to the rolling motion, and are heard 

 squealing and complaining as the ship rolls. 



When a vessel proved a heavy roller, a cure could be made by 

 fitting bilge-keels, but at a permanent loss of speed in all weather, 

 rough or smooth, of a knot or two. Schhck's sea gyroscope will 

 cure .the rolling, with no sacrifice of speed ; it need not be put in 

 action till wanted, and requires little power to keep it going. The 

 gyroscope consists of a heavy horizontal fly-wheel, like this top, 

 harnessed in gimbals, and controlled by a hydraulic buffer in the line 

 of the keel. The damping action of the buffer can be regulated by 

 a valve to salt the period of the waves, and it makes the fly-wheel 

 react against the rolling, and kill it out. The inventor is said to 

 Vol. XXII. (No. 112) x 



