58 PROCEEDINGS OP THE AMERICAN ACADEMY 



The relation of the velocity of local storms to the gradients and the 

 velocity of the cyclonic areas in which they occur, needs still further 

 investigation. The same may be said of the conditions that determine 

 the arrival of some storms early in the day, and of other storms late; 

 the passage of some storms with apparently undiminished strength off 

 the sea-coast and their endurance into the evening, while others act 

 in the opposite way ; and the maintenance of high temperatures after 

 some storms (morning squall of July 21, and 'morning storm of August 

 4), while most are followed by decidedly cooler weather. 



The surface winds flowing towards the storm at a little distance from 

 it, and the squall commonly met blowing outwards in front of the rain 

 area, are well defined on many occasions. The relation of the rain to 

 the out-blowing squall is variable ; in many cases, the former seems 

 to be the effect of the latter ; but in others we have heavy rain and no 

 squall ; sometimes the squall is felt at only a few stations, while the 

 heavy rain is general. Many observers speak of a connection between 

 lightning flashes and an increase in the rain-fall immediately following; 

 it is quite possible that this relation exists, but the evidence usually 

 quoted to prove it does not seem conclusive. 



The more general distribution of storms in the areas of low pressure, 

 their total duration, and the possibility of their surviving the cooler 

 hours of night, are problems that can be better determined by the 

 work of the Signal Service in reviewing the more detailed studies of 

 local services. It is hoped that many of these problems may find their 

 solution in that larger fund of material towards which this report is 

 offered as a contribution. 



rasques.' " This conclusion has been confirmed by other European services, 

 and by Prof. H. A. Hazen in this country. Lieut. Finley has shown that it 

 obtains also for our tornadoes. 



Cambkidge, Mass., June, 1886. 



