146 Atmosplw'ic Origin of the Aurora^ S^c. 



Below is a passage from the paper above referred to, and relates 

 to its different classes of facts, propositions and speculations. It 

 may show that the author has not confounded their different de- 

 grees of evidence. 



' The present article not having been commenced with refer- 

 ence to any comprehensive theory, presents some miscellaneous 

 facts, which are thrown into the common stock for the use of 

 others. Even among the relevant facts, there are, undoubtedly, 

 interesting relations yet to be traced. 2d. The article contains 

 some generalizations, whose results, whilst they may suggest to 

 others a more correct theory, cannot be thereby invalidated. 3d. 

 There are inferences of another class which may be modified, 

 but probably not overthrown by the progress of discovery. For 

 example, that the aurora is an electrical phenomenon ; that it is 

 intimately connected with the elements of clouds, and with these 

 elements only when they are generated in air intensely cold as 

 well as nearly saturated ; and that cirrus clouds of a certain class 

 are intimately connected with auroral action, and that both these 

 phenomena, and also coronse, do, for some reason or other, require 

 a cold adequate to the crystallization of aqueous vapor, are propo- 

 sitions which will not lose all their interest nor any of their truth, 

 even if the discovery should be made that the elements of clouds 

 are essentially globular or vesicular, and that the vapor is not yet 

 crystallized at the time of the phenomenon. It may be neces- 

 sary to remark, that we have not intimated that all snow is not 

 crystallized. On this subject crude notions have prevailed. 4th. 

 As to the views which belong to a more hypothetical class, the 

 author will cheerfully renounce them when a more plausible the- 

 ory shall appear, as they are designed to facilitate, not to limit, 

 investigation. This theory may contain much that is novel, valu- 

 able and true, without being in the highest sense the truth.' 



The individual facts on which the generalizations are founded, 

 cannot be here repeated. Of the second class, or the generaliza- 

 tions, are the following 



'Pi^opositions, 



Which 7nay he regarded as approximately and generally true, 

 in relation to mean results, though not universally, or in relation 

 to each particular instance. 



