$een in London^ September 25, 1827. 419 



to the disciple. Even the history of opinions concerning the 

 Aurora BoreaHs itself, might be cited upon this very point. 



The ordinary and natural resource, in such circumstances, is 

 comparison ; but even comparison has been the source of 

 great and endless errors of description. Of the degree of 

 resemblance proposed between the known and the unknown, 

 there is no common measure for the minds of the hearer and the 

 listener, and the point or points of comparison intended by 

 the first must often be mistaken by the second ; or, if reference 

 is made to a similitude under one aspect, the imagination 

 conceives a resemblance also under another: thus, if it is 

 said, that an unknown animal is as large as a horse, the idea of 

 the figure also of a horse, is apt to be attached, A modem 

 English work of science premises, upon the subject of the 

 Aurora Borealis, that its appearance is so well known as to 

 render description needless. It is true that the work referred 

 to is printed in the Northern part of the island, where the phe- 

 nomenon is doubtless more familiar than in the Southern ; but, 

 in the foregoing pages themselves, it has, perhaps, been de- 

 monstrated as probably certain, that if it is any where suffi- 

 ciently known to render description trite for the common eye, 

 it has at least never hitherto been described with sufficient pre- 

 cision for the aid of speculative research. To attempt to ex- 

 plain its cause^ and to relate its entire history, its appearance 

 must first be either observed or described with accuracy ; and 

 we have seen, above, that some of the most scientific reason- 

 ings which have hitherto been oflfered ae to the former, are 

 wholly inapplicable to the true peculiarities of the latter. 



Considered simply as a visual object, and as a meteor 

 differing from all others, and especially from all other luminous 

 meteors, in this, that its duration extends to hours, if not to 

 days and months ; the only resemblance, perhaps, that can be 

 suggested, is to that description of lightning which is called heat- 

 lightning^ the frequent companion of our summer-evenings. 

 But, here, the similitude is inexpressibly feeble ; since heat- 

 lightning has nothing, either of the splendour, the volume, or 

 the beauty of the Aurora ; and since the light of the latter, 

 however mobile, varied, and, from time to time, increased and 

 diminished in itself, is yet, as to general effect, continuous and 



