PHYSICS OF THE GLOBE. 169 



penmen tally. The latter illustrate the subject by investi- 

 gating the movement of a chain hanging loosely over a pul- 

 ley, around which it is rapidly running. The various curi- 

 ous curves into which it twists itself are fairly explicable by 

 a proper application of the laws of centrifugal force, and the 

 elasticity and rigidity that are imparted to the chain by its 

 motion remind one of the properties of vortex rings of air or 

 water. The allied mechanical principles here involved will, it 

 would seem, also find an application in some phenomena of 

 meteorology, especially those of tornadoes. These views were 

 first communicated two years ago by Aitken to the Royal 

 Society of Edinburgh, but have only recently been published. 



The students of vortex motion will find some valuable 

 chapters in the last volume of the Proceedings of the Royal 

 Society of Edinburgh, which, although delivered in 1875, 

 have only come to hand the past year. The first paper, on 

 Vortex Statics, by Sir William Thomson, concludes with a 

 brief statement of the general propositions, definitions, and 

 principles. The paper itself deals with the steady motion of 

 vortex rin^s. The cases are considered in which one circu- 

 Jar vortex ring is linked with another, and where three or 

 more rings are mutually interlinked ; the cases of trefoil 

 knots, nine-leafed knots, and much more complicated figures 

 are also considered. Further papers on the same subject are 

 also promised. 



At the reunion of French scientists at the Sorbonne, Pro- 

 fessor Hebert, of Mulins, read a paper on the General Move- 

 ments of the Atmosphere. From the Signal Service tri-daily 

 weather-charts he concludes that the Atlantic storms have 

 their origin in the Rocky Mountain district, being produced 

 by the friction of the equatorial current against the moun- 

 tain-tops. These tourbillions follow the river-courses to the 

 Gulf of St. Lawrence, and there form the great depressions 

 which start across the Atlantic ; and we need hardly say 

 that Mr. Hebert's conclusions differ widely from the views 

 held by American meteorologists. 



A contribution to our knowledge of the effect of winds on 

 the gradient of rivers (and inversely to the friction of wind 

 over water) is given in a paper, by W. H. Searles, on the 

 Levels of Portions of the Erie Canal. lie finds the probable 

 error in 136 miles of most careful levelling to be 0.103 foot. 



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