274 THE WEATHER 



straight out from the center, and it makes the winds of a LOW 

 curve around the center instead of blowing straight toward the 

 center (see Fig. 179). This turning or deflection of the winds 

 is in accord with the law of mechanics first applied to the 

 atmosphere by Wm. Ferrel/ an American meteorologist, 

 shortly before 1860. This law may be stated as follows: 



299. Law of a Moving Body on a Rotating Surface (Often 

 Called "FerrePs Law"). Any moving body on a rotating 

 surface will travel in a curved path. If the surface rotates 

 counter-clockwise (opposite the movement of the hands of a clock) , 

 the path will curve to the right; if the surface rotates clockwise, the 

 path will turn toward the left. 



Exercise 61. "FerrePs Law" Illustrated Counter-clockwise Motion 



Procure a smooth level table, a cardboard 2 or 3 ft. in diameter, a 

 marble, and two wire nails. Drive one nail through the center of the 

 cardboard into the table to serve as an axis. Push the other nail up 

 through the cardboard from the under side 

 about 5 in. from the center, to serve as a 

 handle for turning the cardboard. 



1. While one person revolves the card- 

 board steadily counter-clockwise at the rate 

 of about two or three turns per second, 

 another should roll the marble rather swiftly 

 across the cardboard. A little experiment- 

 ing will be necessary to find the proper speed 

 for the marble. It should not roll too 

 swiftly, or the cardboard will not have time 

 to turn much while it is crossing. If the 

 FIG. 203. marble rolls too slowly, it may stop and be 



carried around by the cardboard. After 



finding the best speed, dip the marble in ink before rolling. Then 

 roll it across the cardboard in several directions. Notice that 

 when the marble is rolled in the direction a-b, Fig. 203, its path on 

 the revolving cardboard makes the curved line a-n, and when it is 

 rolled along the line c-d, its path curves to c-r. 



2. Lay a yard stick on small blocks so that it extends across and 

 above the cardboard. Hold the yardstick firmly in place and draw 

 a pencil along it while the cardboard is revolving under it. Do this 



1 Note: It had been previously stated by Coriolis and others. 



