298 David S. Price, Esq., on a New Test for Iodides. 



under the origin of the aurora situated in space; finally, 

 from the periodicity of the exhibitions, — the diurnal, which 

 shows a relation to the position of the sun with respect to 

 the horizon, — the annual, which indicates a relation of the 

 auroral body to the earth's orbit, — and especially the secular, 

 implying 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 periodicity takes the phe- 

 nomena out of the pale of terrestrial, and places it within 

 the pale of astronomical causes. In the second place, we 

 infer that the auroral body, whence the material of the 

 aurora is derived, is a nebulous body, consisting of exceed- 

 ingly light, inflammable, semi-transparent, magnetic matter ; 

 that it has a revolution around the sun ; that probably there 

 are many such collections of nebulous matter diffused through 

 the planetary spaces, each having a revolution and period of 

 its own ; and that the phenomena of the aurora arise from 

 one of those coming occasionally into the earth's sphere of 

 attraction. In conclusion, we endeavour to shew that the 

 cause here assigned and proved to exist is adequate to account 

 for the leading facts of the case, as the great extent and 

 velocity, the geographical position, the magnetic relations, 

 and the periodicity ; while, in regard to the minor facts, it is 

 inconsistent with none, although it may not be ready to ex- 

 plain them all until all the modifying circumstances are fully 

 understood. 



It may be remarked that there is, in my view, a great 

 analogy in the origin of the aurora borealis and of meteoric 

 showers. I hope hereafter to be able to develop this analogy 

 more fully than can be done on the present occasion, and to 

 investigate the question of any possible connection of either 

 phenomenon and the zodiacal light. 



On a New Test for Iodides. By David S. Price, Ph. D., F.C.S. 



Having in a preceding paper pointed out the principle 

 on which the detection of nitrites by means of iodide of pot- 

 assium and hydrochloric acid depend, I shall proceed briefly 



