406 PHYSICAL GEOGRAPHY OF THE SEA, AND ITS iMETEOEGLOGY. 



conjecture, as the probable result of observation, that the greater 

 tlie distance between the place of high and low barometer, the 

 less the velocity of wind for a given barometric difference would 

 be. Professor Buys Ballot has discovered, practically, the nume- 

 rical relation between the force of the wind and given barometric 

 differences for certain places in Holland. ' With the vievv of 

 ascertaining like relations for this country, it has been proposed 

 to establish a cordon of meteoroloorical stations over the United 

 States, each station being required to report daily to the Obser- 

 vatory in Washington, by telegraph, the height of the barometer, 

 force of wind, etc. By such a plan, properly organized, we 

 might expect soon to be able to give the ships, not only on the 

 great lakes, but in our sea-port towns also, timely warning of 

 many a gale, and to send by telegraph to Europe — when one 

 shall be paid — warning of many a one long before it could tm- 

 verse the Atlantic. Tlie contributions which the magnetic tele- 

 graph is capable of making for the advancement of meteorolog}'- 

 will enable us to warn the ships in our Gulf ports, as well as 

 those of Cuba, of the approach of every hurricane or tornado that 

 visits those res^ions. 



791. But, returning to the cyclone theory: though the wind 

 The changing of the be blowing around in spirals against the hands of 

 wind in a cyclone, ^i^q watch, yet, from the fact that the centre about 

 which it is blowino^ is also travelling: alons^, the chano^es of the 

 wind, as observed by a vessel over which the storm is passing, 

 will not, under all circumstances, be against the sun in tlie 

 northern, or with the sun in the southern hemisphere. The 

 reason is obvious. This point is worth studying, and any one who 

 will resort to " moving diagrarns " for illustration will be repaid 

 with edification. Piddington's horn cards 

 are the best ; but let those who have 

 them not cut a disc of paper of any con- 

 venient diameter, say 2J inches, and then 

 cut out a circle of 2 inches from the middle ; 

 this will leave a ring half an inch broad 

 upon which to draw arrows representing 

 the course of the wind. Suppose tlieni to be 

 drawn for the northern hemisphere, as in 

 the annexed diagram ; lay the paper ring 

 on the chart : suppose the ship to be in the N.E. quadrant of 

 the storm, which is travelling north, the centre of the storm 



