THE ENTOMOLOGIST. 57 



islands, we have become impressed wilh the fact that the 

 largest flights of birds occur there during the period of great 

 atmospheric disturbance. From the latter end of September 

 to that of October, violent revolving gales are prevalent 

 throngliout the region which comprises the east coast of the 

 Southern and Middle* States and the North Atlantic in those 

 latitudes, for some 600 or 800 miles from land. At this par- 

 ticular period vast flights of birds of all kinds are proceeding 

 southward along the coast for their winter resorts in Florida, 

 West Indies and South America, and must often meet with 

 the violent gales we have alluded to. Now the observations 

 of scientific aeronauts, like Glaisher and others, teach us 

 that the upper atmosphere is composed of currents of air 

 differing in their courses as elevation proceeds, and some 

 cases are on record in which balloons at a great height have 

 suddenly come in contact with violent direct gales, which 

 carried them onward with such velocity as to render their 

 course one of extreme peril, only escaping destruction by 

 the superior manoeuvring of those in charge. Let us suppose 

 a violent revolving gale passing along the coast of the 

 Southern States, about the latitude of the Bermudas, during 

 the period of the autumnal migration of birds and butterflies, 

 engulfing some of those great flights which are then proceed- 

 ing along in a southerly direction. Drawing them up high 

 in its vortex, a direct westerly gale is met with, blowing with 

 great force out to sea. Hurled with amazing rapidity along 

 this cool aerial current, in the course of about three or four 

 hours the heated vapour arising from the Gulf Stream would 

 be met wilh ; and would it be considered as too imaginative 

 to grant that the ascending warmth of that stream has power 

 sufficient to ameliorate the condition of the cool current, to 

 stay its rapid course and allow the animal freight to descend, 

 which, then within a comparatively short distance of the 

 Bermudas, would seek the nearest land by that instinctive 

 impulse so characteristic of these tribes, and aided perhaps 

 by perfect calm or favouring breeze, arrive at those distant 

 isles, without encountering the dangers which — in the form 

 of contrary winds — would most certainly accompan}^ an 



* Terias Lisa occurs aloug the Atlantic Coast from New Hampshire to 

 Cuha. It is excessivel}' rare north of Cape Cod, common from New Jersey to 

 Cape Hatteras, and extremely abundant farther south. — S. H, S. 



