488 Intelligence and Miscellaneous Articles. 



The publisshed accounts show that the Orgueil meteor was first 

 seen at an altitude greater than 55 miles, that it exploded at an 

 altitude of about 20 miles, and that it was descending in a line in- 

 clined at the least 20° or 25° to the horizon. The velocity must 

 have been not less than 15 or 20 miles per second. This example 

 affords the strongest proof that the stone-producing meteors and the 

 detonating meteors are phenomena not essentially unlike. — Silliman's 

 American Journal for March 1865. 



PHENOMENON IN THE INDUCTION-SPARK. BY E. FERNET. 



The disengagement of heat which the induction-spark produces in 

 the air exerts upon the path of this spark an influence which seems 

 to be shown by the following experiment. 



Two small straight brass rods about 2 decimetres in length, each 

 upon an insulating support, are placed almost vertically and parallel 

 to each other at a distance of a few centimetres ; they are then 

 moved somewhat apart above, so that they form below a very acute 

 angle. They are then both united with the ends of the induction- 

 coil of a Ruhmkorff's apparatus. The sparks which pass at each 

 oscillation of the commutator appear first, as is natural, between 

 the two nearest points of the bars — that is, at the bottom. But they 

 soon leave this and appear at a higher part, until they reach the 

 highest, when this discharge suddenly ceases. The spark now 

 passes below, and the same series of phenomena is repeated. The 

 duration of the impression has, moreover, the effect that not merely 

 one line of light is seen, but several are seen close together — a sort 

 of ladder with very brilliant rounds in the dark, which slowly and 

 regularly ascends between the vertical bars, breaks off, and then 

 again begins from below without ever exhibiting the inverse direction. 



These results appear to be explained by the heating in the dis- 

 charge. The passage of each spark produces in the air a consider- 

 able increase of temperature, the air expands, ascends, and thus the 

 upper layer, though longer, offers less resistance, in consequence 

 of which the second spark passes here. The passage of the second 

 acts just in the same way upon the third, and so forth, until the dis- 

 charge takes place on the uppermost points. The air continues to 

 ascend ; but the spark betakes itself where the layer of air is shortest, 

 that is, to the lowest point. 



This explanation is supported by a change of the experiment. 

 For if the bars are placed in a horizontal, and not a vertical plane, 

 still somewhat divergent, no displacement is observed, but the spark 

 always passes between the nearest points. This is also the case if 

 the bars are vertical but converge above. Even in the first position 

 of all, the ascent of the spark can be suddenly suppressed, if a current 

 of air from above is directed upon it. — Comptes Rendus, vol. lix. 

 p. 1005. 





