May 5, 1905.] 



SCIENCE. 



705 



versities are the chief means for the advance- 

 ment of science and since the results would 

 liave direct relation to the work of instruction, 

 a plan might be devised by which a number 

 of universities would jointly provide for it. 



In conclusion, if this be thought worthy of 

 further discussion, let the motive of _ the 

 writer's suggestion be clear. It is the ad- 

 vancement of science in America by means of 

 organized reviewing of current literature as 

 an aid in the development of the future in- 

 vestigator. This may be regarded by some as 

 in the nature of ' coddling ' which would lead 

 into scientific work those who are unfit and 

 who would not succeed. No one is less in- 

 clined than the writer to give undue encour- 

 agement to students. On the other hand it is 

 an open question whether science is not now 

 losing fit persons for want of some such intro- 

 duction to the workshop. It is not desired 

 that the literature should be brought down to 

 the level of the average student. The reviews 

 should be written for the serious man who is 

 seeking his proper place and the opportunity 

 to do work. J. B. Johnston. 



Naples, 



November 29, 1904. 



THE ORIGIN OF CYCLONES, TORNADOES AND COLD 

 WAVES. 



To THE Editor of Science : As it seems still 

 to be held that the origin of cyclones, tor- 

 nadoes and cold waves is matter of debate I 

 beg to offer a resume of an article on that 

 subject contributed some twenty years ago 

 to the Educational Courant of Louisville, Ky., 

 and which at the time received somewhat ex- 

 tensive notice. 



The contention of that article was that 

 cyclones arise exclusively over tropical islands. 

 It is quite obvious that the movement of the 

 atmosphere over every island that has a sea- 

 breeze as well as above every local fire, must 

 be cyclonic. The vast majority of such cy- 

 clonic movements disappear with the reversal 

 of the breeze which occurs at night. But now 

 and then, under particularly favoring condi- 

 tions, it happens that over a tropical island 

 the cyclonic movement gains such force as 

 to enable it to ascend to a great altitude, and 



this results in such concentration of ^apor 

 and consequent evolution of heat as to supply 

 a new force for the continuation of the move- 

 ment. 



Now the trade winds on their equatorial 

 border describe a loop, while passing from the 

 southwesterly movement below to the north- 

 easterly above, in such way that the wind in 

 those situations may be very swift at consid- 

 erable altitudes over regions of calm below. 



Say one of the daily cyclones described 

 arises over one of the Cape Verde Islands off 

 the coast of Africa, or over one of the Wind- 

 ward islands, and let the conditions be such 

 that when the cyclonic movement attains a 

 considerable height it is caught in the loop 

 of the trade winds moving to the westward. 

 It will be carried to the west along the 

 southern border of the loop, the strength of 

 the southerly flow of the trade winds being 

 sufficient to prevent the upper return or 

 northerly flow from carrying it to the north. 

 But in the course of its journey it enters a 

 region where friction due to the continental 

 mainland has largely interfered with the trade 

 winds, and which interference has resulted in 

 a weak movement of the trade winds of the 

 surface as compared with the return winds 

 above — this retardation after the cyclone 

 has turned and begun its journey to the east- 

 ward. There must then be some close con- 

 nection between them; a - connection that 

 would suggest the relation of cause and effect. 

 But how can the low produce the high and its 

 resulting cold wave. If we take into con- 

 sideration the three facts that the cyclone 

 itself is moving eastward at the rate of 20 

 or more miles an hour; that at the same time 

 it is revolving contra-clockwise so that its 

 northern segment has a potential westward 

 movement of thirty or forty miles per hour; 

 and, third, that there is a constant eastward 

 movement of the upper strata of the atmos- 

 phere at a rate of perhaps seventy-five miles 

 per hour — the situation becomes much sim- 

 plified. 



The periphery of the cyclonic mass on its 

 northern side, moving as it does to the west, 

 meets the air of the constant eastward current 

 and backs or dams it up, thus producing 



