684 KANSAS CITY REVIEW OF SCIENCE. 



upon every point of the rock-prison. The intensity of the resultant will be repre- 

 sented by the aggregation of the resultants of all the particles of water. Suppose a 

 small opening be made in the rock-prison. Immediately the water will be forced 

 out with a velocity equal to the influence of these aggregated resultants, modified 

 by the laws of friction, and this velocity will not be influenced by the direction 

 of the original impulses given to the water particles. Hence, if fissures exist in rocks 

 that lead to imprisoned waters, it would happen that through these outlets the wa- 

 ters must certainly flow. If by any artificial means, as by boring, an opening should 

 be made between a body of confined water and the surface of the earth, a flowing 

 well would result. The intensity of the centrifugal force will increase with the 

 distance from the earth's center, while gravity decreases. Thus we find* the 

 strongest and most abundant flows at the tops of mountains or on high plateaus. 



But, suppose that it had been fully proved that a particular overflowing 

 well or spring was caused by hydrostatic pressure, it would still remain to be ac- 

 counted for how the water got to that higher point. This can best be done by 

 the force designated, which is always acting upon the partially confined water- 

 beds and water-channels forming the internal water structure of the earth's crust. 



THE AURORA BOREALIS. 



PROF. G. T. TEMPLE. 



Although the conjecture was hazarded more than 160 years since by Halley,that 

 the aurora borealis was a magnetic phenomenon, it has acquired empirical certainty 

 from Faraday's discovery of the evolution of light by magnetic forces, as well as 

 from more recent observations, the following extracts are translated from a letter 

 written by Herr Pastor emeritus H. M. F. Esmark, having observed the meteor- 

 ological conditions attending the display of the polar lights for many successive 

 years : " The aurora is neither seen during extreme cold or northerly winds, but 

 appears when an ordinary arctic temperature is raised by southerly and westerly 

 winds, and is generally followed by snow. In the southeastern part of Norway it 

 seems to be especially caused by southeasterly winds, which are there very moist and 

 rather warm. Its appearance is aways accompanied by a falling barometer. In 

 my opinion the phenomenon is due to the following causes : When a wind laden 

 with warmth, moisture, and electricity comes in contact with a body of cold air, 

 the moisture is converted into snow, the warmth and electricity are thereby re- 

 leased, and the aurora is the result of the disturbances. The northern lights can 

 not occur in very high latitudes, because the warm, moist air is cooled long before 

 it reaches them." In this way Herr Esmark would account for the splendid ap- 

 pearance of the aurora in Northern Norway, where the sea winds, bringing 

 warmth, moisture and electricity from the ocean, are met by cold land winds from 

 the interior. MM. Lottin, Bravais, and Siljerstrom, who spent a winter in Bose- 

 kop, in Alten ( lat. 70 N.), saw the northern lights 160 times in 210 nights. The 

 most vivid aurora that I ever saw near Alten, was toward midnight on the 12th of 

 November, 1874. The flickering lights played about the masthead so like ligh t 



