«>88 Intelligence and Miscellaneous Articles. 



(especially at a small negative one) immersed in liquids when the 

 current is of considerable intensity. 



According to Colley, in a rotating mirror a series of bright stars 

 irregularly distributed upon a feebly illuminated ground are at the 

 same time perceived : so that consequently the individual discharges 

 issue from different parts of the electrode, while the time of the 

 passage of the current is very short in comparison with that of the 

 intermissions. 



The spectrum at a negative electrode of platinum in dilute sul- 

 phuric acid shows, when 96 Buusen elements are employed, at first 

 the red (bright) and blue hydrogen-lines. In solutions of chloride 

 of sodium and chloride of lithium the lines of those metals are seen 

 in addition, and also (particularly five) platinum-lines are well seen. 

 Only by chance is the electrode herewith so strongly heated that 

 the liquid no longer wets it. The passage of the spark cannot be 

 owing to this, since the electrode may be quite cold and vet lumi- 

 nous. In order to prove this, Colley fixes in the neck of an inverted 

 flask without a bottom a glass tube, in the upper end of which a 

 platinum tube is cemented, and conducts a stream of cold water 

 through. The flask is filled up to about 1 millim. above the upper 

 extremity of the glass tube with dilute sulphuric acid, into which a 

 cylinder of platinum foil dips. If the platinum tube, only a small 

 surface of which is in contact with the sulphuric acid, serves as the 

 negative, the foil as the positive electrode, yet the light appears. 

 From this it follows that the high temperature really falls upon the 

 liquid surrounding the electrode, which, on account of its small 

 surface, opposes a great resistance to the current. As can easily 

 be calculated, a current from 100 Bunsen cells could in fact readily 

 heat to ebullition dilute sulphuric acid (4-) close to an electrode of 

 10 square millims. surface, whereupon the passage of the sparks 

 then ensues in the vapour, while the rest of the liquid and the elec- 

 trode are only secondarily heated. Even when, in a narrow aper- 

 ture, sparks are formed in the liquid itself, as Eighi has observed, 

 this arises from the formation of vapour there in consequence of 

 the great resistance and the corresponding heating of the liquid. — 

 Wiedemann's BeiUdtter, 1880, No. 9, pp. 684, 685. 



PHOTOGRAPHS OF THE NEBULA IN ORION. 

 BY PROF. HENRY DRAPER, M.D. 



During the night of September 30, 1880, I succeeded in photo- 

 graphing the bright part of the nebula in Orion in the vicinity of 

 the trapezium. The photographs show the mottled appearance of 

 this region distinctly. They were taken by the aid of a triple ob- 

 jective of 11 inches aperture, made by Alvan Clark and Sons, and 

 corrected especially for the photographic rays. The equatorial 

 stand and driving-clock I constructed myself. The exposure was 

 for fifty minutes. I intend at an early date to publish a detailed 

 description of the negatives. — Silliman's American Journal, Novem- 

 ber 1880. 



New York, October 2, 1880. 



