Electrification of Effluvia from Chemical Reactions. 21 



(3) The principal applications of the methods herein 

 described are the measurement of the apparent magnitudes of 

 very small or very distant sources of light such as planetoids 

 and satellites (though larger bodies are not excluded) , and of 

 the angular distances between very close double stars. 



(4) On account of the narrowness of the interference- 

 fringes when a very minute body is under examination, the 

 method of obtaining these fringes (by a pair of adjustable 

 slits in front of the objective of a telescope) is open to objec- 

 tion, from which the refractometer method is entirely free. 

 Further, this last modification makes it possible to extend the 

 effective aperture of the equivalent telescope without limit. 

 Thus, while it would be manifestly impracticable to construct 

 objectives much larger than those at present in use, there is 

 nothing to prevent increasing the distance between the two 

 mirrors of the refractometer to even ten times this size. If 

 among the nearer fixed stars there is any as large as our sun, 

 it would subtend an angle of about one hundredth of a second 

 of arc ; and the corresponding distance required to observe 

 this small angle is ten metres, a distance which, while utterly 

 out of question as regards the diameter of a telescope-objective, 

 is still perfectly feasible with a refractometer. There is, 

 however, no inherent improbability of stars presenting a 

 much larger angle than this; and the possibility of gaining 

 some positive knowledge of the real size of these distant 

 luminaries would more than repay the time, care, and 

 patience which it would be necessary to bestow on such a 

 work. 



In concluding, I wish to take this opportunity of expressing 

 my appreciation of the disinterested manner in which my 

 efforts have been so ably and zealously seconded by Mr. F. 

 L. 0. Wadsworth, Fellow of Clark University. 



II. On the Electrification of the Effluvia from Chemical or 

 from Voltaic Reactions. By J. Brown *. 



1. 1/^ROM the series of very interesting experiments pub- 

 J- lished in the January number of this Journal, p. 56, 

 Mr. J. Enright concludes that nascent hydrogen and other gases 

 become positively electrified by contact with acids, and nega- 

 tively by contact with salts in solution. The line of experiment 

 struck out by Mr. Enright will, I think, afford valuable aid 

 in investigating electrochemical hypotheses ; but it would 



* Communicated by the Secretaries of the Electrolysis Committee of 

 the British Association. 



