B. TERRESTRIAL PHYSICS AND METEOROLOGY. 95 



peculiarities of its own. Thus the average annual rainfall 

 at Nagpur is 40.7 inches, of which 37.5 fall in the monsoon, 

 and 3.2 in the dry season. Of this latter quantity, no part 

 flows from the ground into the reservoir; and the records of 

 the discharge of the drainage area are confined to about 

 four months. The total depth evaporated during this time 

 amounted to about four feet, or an average of about one fifth 

 of an inch per day. The total loss of water during the season 

 from the reservoir from all causes amounted to 104,000,000 

 cubic feet, out of which 55,800,000 cubic feet was evaporat- 

 ed, leaving 48,200,000 cubic feet as used or absorbed. An 

 extensive comparison is given by the author between solar 

 spots and India rainfall ; but no very satisfactory conclu- 

 sions are drawn by him. Minutes of the Institution of Civil 

 Engineers, XXXIX., Part I, 16. 



MAGNETIC DISTURBANCES AND AURORAS IN THE ARCTIC 



REGIONS. 



Lieutenant Weyprecht reports that the magnetic disturb- 

 ances in that portion of the arctic regions visited by the 

 Austro-Hungarian North Polar Expedition are of extraor- 

 dinary frequency and magnitude, and are closely connected 

 with the aurora borealis ; the disturbance being the greater 

 and quicker the more convulsive the motion of the rays of 

 the aurora and the more intense the prismatic colors. Quiet 

 and regular arcs, without motion of light or radiation, exer- 

 cised almost no influence upon the needles. In all disturb- 

 ances the declination needle moved toward the east, and the 

 horizontal intensity decreased, while the inclination increased. 

 Movements in an opposite sense, which were very rare, can only 

 be looked upon as movements of reaction. Weyprecht had 

 expected to be able to connect the aurora with the gal- 

 vanic earth current ; but being far distant from the land, he 

 was obliged to bury his connecting plates in the ice, in con- 

 sequence of which the movements were too feeble to be ob- 

 served. A similar failure attended the attempt to observe 

 the atmospheric electricity. He found that storms followed 

 almost every time after intense auroras, and thinks he is jus- 

 tified in the conclusion that the aurora is an atmospheric 

 phenomenon, and closely connected with meteorological con- 

 ditions. 12 A, XL, 368, 397. 



