1 66 LIGHT SCIENCE FOR LEISURE HOURS. 



channel becomes a storm-track, like the corresponding 

 channels over the warm ocean-currents. The extreme 

 violence of land-storms is probably due to the narrow- 

 ness of the track within which they are compelled to 

 travel. For it has been noticed that the fury of a 

 sea-cyclone increases as the range of the ' whirl ' 

 diminishes, and vice versa. 



There seems, however, no special reason why cy- 

 clones should follow the storm- C in one direction 

 rather than in the other. We must, to understand 

 this, recall the fact that under the torrid zones the 

 conditions necessary for the generation of storms prevail 

 far more intensely than in temperate regions. Thus 

 the probability is far greater that cyclones should be 

 generated at the tropical than at the temperate end of 

 the storm-C. Still, it is worthy of notice, that in the 

 land-locked North Pacific Ocean, true typhoons have 

 been noticed to follow the storm-track in a direction 

 contrary to that commonly noticed. 



The direction in which a true tornado whirls is 

 invariably that I have mentioned. The explanation 

 of this peculiarity would occupy more space than 

 I can here afford. Those readers who may wish 

 to understand the origin of the law of cyclonic ro- 

 tation should study Herschel's interesting work on 

 Meteorology. 



The suddenness with which a true tornado works 

 destruction was strikingly exemplified in the wreck of 

 the steamship * San Francisco.' She was assailed by 

 an extra-tropical tornado when about 300 miles from 



