273 Prof. Magnus on an Apparatus for the illustration 



Guinea, passes between New Caledonia and the Navigators' 

 Islands, and extends to tlie volcanoes of New Zealand. 



It is obvious that the curvature of the storm-tracks of the 

 South Pacific Ocean is of the same kind as that of the east coast 

 of Australia ; and the storm-tracks of the South Indian Ocean 

 have likewise the same kind of curvature as the west coast of 

 Australia. This relation holds equally in the case of the West 

 Indian cyclones, and the coasts which they traverse. These 

 observations may probably contain the germ of a law of pro- 

 gressive motion of cyclones more general ih&u that of their initial 

 westerly progression. 



Hobart Town, April 25, 1853. 



XL. Improved construction of an Apparatus for the illustration of 

 various phenomena of Rotating Bodies. JB?/ Professor Magnus*. 

 [With a Plate.] 



IN a paper of mine on the deviation of projectiles, I have 

 drawn attention to a remarkable phajuomenou which is ex- 

 hibited during a body's rotation, and described an apparatus in- 

 tended for the purpose of illustrating the motion of cylindi'o- 

 conical projectiles, and of showing that the axis of a rotating body 

 is fixed only under the condition that it is perfectly free, being, 

 on the contrary, quite mobile when it is prevented from moving 

 in one direction. 



I have had this apjjaratus constructed in a modified form, 

 which renders it more convenient for experiment, and at the 

 same time alterations are introduced which render it possible to 

 observe with this instrument the various remarkable pha^nomena 

 exhibited by rotating bodies more completely than has hitherto 

 been attainable. 



The new construction is represented in figs. 1 and 2, Plate IV, 

 AB and CD are two brass discs with thick edges, 3' 8 inches in 

 diameter, which having their axes ab and cd placed between points 

 in the stirrups abfg and cdhk, arceasily moveable. The stirrups 

 are attached to the bar mn, which is held fast in the collar os by 

 the screw e, and with this collar is free to move round the hori- 

 zontal axis qr between two points, q and r, attached to the forked 

 piece pqr. The forked piece is carried by the axis viv, which 

 is pointed underneath. The entire apparatus, therefore, rests 

 upon the point at tu, and hence is free to move round a vertical, 

 as also round a horizontal axis. 



In order to check the one or the other of these motions, the 

 piece of brass pu is so attached at p to the forked piece pqr, that 

 * From PoggendorfF's Annalen for Febniary, 1854. 



