NATURAL PHILOSOPHY. 117 



nations or atmospheric precipitations. Secondly, from the velocity of 

 the motions, which are too great for any terrestrial forces. Thirdly, 

 from the occurrence of the different stages of an aurora (the beginning, 

 maximum, and end) at the same hour of the night, in places differing 

 widely in longitude, which indicates that successive portions of the 

 earth, in the diurnal rotation, come under the origin of the aurora situ- 

 ated in space. Finally, from the periodicity of the exhibitions ; the 

 diurnal, which shows a relation to the position of the sun with respect 

 to its position ; the annual, which indicates a relation of the auroral 

 body to the earth's orbit ; and especially the secular, which implies a 

 cycle, at the end of which the auroral body and the earth return to the 

 same relative position in the heavens, while the very existence of such 

 a secular periodicity takes the phenomenon out of the pale of terres- 

 trial, and places it within the pale of astronomical causes. This theory 

 also infers that the auroral body (whence the material of the aurora is 

 derived) is a nebulous body of light, semi-transparent, inflammable 

 and magnetic matter, revolving around the sun ; and that probably 

 there are many such collections of nebulous matter diffused through 

 the planetary spaces. It may be remarked that there is, according to 

 these views, a great analogy in the origin of the aurora borealis and 

 of the meteoric showers. 



EFFECTS OF ATMOSPHERIC ELECTRICITY UPON THE WIRES OF 



THE MAGNETIC TELEGRAPH. 



THE Revue Scientifique for December, 1849, contains an interesting 

 article by Mr. Baumgartner on the above subject. The following are 

 some of his results. 1. The needle rarely coincides with the point 

 w'hich is determined by its astatic state and the tension of its suspen- 

 sion thread ; this shows it to be influenced by an electric current. 

 2. The variations are of two kinds ; there are some which reach 50, 

 others extend over 3 or 8'. The first are less frequent, and they differ 

 so often in direction and intensity that it is impossible to deduce a law 

 for them. The small deviations appear connected by a very simple 

 law. The observations made at Vienna and at Gratz appear to show 

 that, during the day, the electric currents move from Vienna and from 

 Gratz to Semmering, which is more elevated. This direction is in- 

 verse during the night. The changes occur after the rising and setting 

 of the sun. 3. The regular current is less disturbed by the irregular 

 one when the air is dry and the sky serene, than w r hen the weather is 

 rainy. 4. In general, the current is more intense with short than with 

 very long conductors ; often, even, the current of the longer chain is 

 opposed to that of the shorter one. Where there is a difference of in- 

 tensity it is far greater than that which could originate from the resist- 

 ance of the longer conductor. When the sky is cloudy and the 

 weather stormy, there are frequently observed in the electric con- 

 ductor currents sufficiently intense to affect the telegraphic indicators, 

 which are, however, far from having extreme sensitiveness. In pla- 

 cing the conducting wires of the northern telegraph line from Vienna, 

 the workmen frequently felt a kind of spasm in handling the wires, 



