A\ ELECTRICAL EXPLOSIOX. 24t 



auroras should have happened to increase so much, just as the night of 

 ignorance was dispersed by the revival of learning through the agency 

 of the art of printing, and the earth and sky were observed and ques- 

 tioned under the Baconian philosophy. Upon a view of the whole sub- 

 ject, then, we incline to the opinion that the supposition of the secular 

 character of the aurora has no foundation in fact, and that all theories 

 which attempt to account for it are worthless. The phenomenon has 

 indeed itsvariations, just as the weather has, but it is believed they are 

 confined comparatively within narrow bounds. 



//. The disturbance of the Magnetic JVeedle. 

 This is an interesting and important effect accompanying the aurora. 

 It is, however, a variable effect. It is different for different places, even 

 during the same display ; amounting, in some localities, to as much as 

 9° or 10° in several hours, in others to less than 1°, and, as asserted by 

 some observers, in others being equal to 0°. But however this may be 

 the disturbance of the magnetic needle, both in declination and dip, is a 

 constant effect of the aurora. In almos't all the instances observed with 

 sufficient care the needle was caused to decline more eastward than 

 westward of its mean position at other times. It is not much affected 

 by the arch, or the diffused light, or the bank of luminous matter in the 

 horizon; but it is very much disturbed by the crimson columns, and 

 whenever the streamers are in a state of great activity. It thus gives 

 evidence of the existence of an aurora, which cannot be seen on account 

 of a clouded sky, or the light of day. It has even given information in 

 the United States of an auroral display taking place in Europe, but of 

 which no evidence was furnished to the eye. 

 ( Conclusion in our next.) 



An Electrical Explosion. — On the 10th of August ult., at about 

 9§ o'clock, p. M., I witnessed what seemed to be the explosion of a cloud 

 by electricity. Having, for a few moments, watched a very active thun- 

 der-cloud, for the purpose of knowing the precise direction it was taking, 

 I was, immediately upon looking away, startled by an intense glare of 

 light, which completely obliterated every thing from my sight, and which 

 was in about a second afterwards, followed by such a thunder-crash as 

 made me, momentarily, feel as if the heavens were about tumbling down. 

 As soon as I could distinguish objects again, I looked up, and was sur- 

 prised to find that the cloud, whose well-defined and rounded summit 

 had just, a few seconds before, ranged with two bright stars, about 30° 



