438 WRITINGS OP JOSEPH HENRY. [1859 



ON THE APPLICATION OP THE TELEGRAPH TO THE PREMONI- 

 TION OP WEATHER CHANGES. 



(Proceedings American Academy of Arts and Sciences, vol. iv, pp. 271-275.) 



August 9, 1859. 



Professor Henry made a verbal communication relative 

 to the application of the telegraph to the prediction of 

 changes of the weather, particularly in the city of Boston 

 and its vicinity. 



It has been fully established by the observations which 

 have been made under the direction of the Smithsonian 

 Institution, and from other sources of information, that the 

 principal disturbances of the atmosphere are not of a local 

 character, but commence in certain regions, and are propa- 

 gated in definite directions over the whole surface of the 

 United States east of the Rocky Mountains. 



From a careful study of all the phenomena of the winds 

 of the temperate zones it is inferred that over the whole sur- 

 face of the United States and Canada there are two great 

 currents of air continually flowing eastward. These cur- 

 rents consist of an upper and a lower, the former returning 

 the air to the south which was carried by the latter towards 

 the north. The lower current, which is continually flowing 

 over the surface of the United States, is about two miles in 

 depth, and moves from the southwest to northeast. The 

 upper or return current, which is probably of nearly equal 

 magnitude, flows from northwest to southeast, or nearly at 

 riaht angles to the other, and the resultant of the two is a 

 current almost directly from the west. The reaction of these 

 two currents appears to be the principal cause of the sudden 

 clianges of weather in our latitude. They give definite direc- 

 tion to our storms, accordingly as the latter are more influ- 

 enced by the motion of the one or the other of these great 

 aerial streams. The principal American storms may from 

 our present knowledge, be divided into two classes, namely 

 those which have their origin in the Caribbean Sea and 



