18 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



Perhaps the strangest feature observed in connection with 

 the spectrum of Encke's comet was the progressive shifting 

 of the point of maximum brightness in its middle band. The 

 observed wave-lengths of the light of this point, on different 

 nights, are aproximately as follows: November 18,501.0; 

 November 25, 505. V; November 26, 505.9; "November 27, 

 510.0; November 29,510.0; December 1,510.9; December 

 2, 511.9. It should be stated that while these changes were 

 ffoino- on the band increased in breadth. 



The comet was examined carefully with a double-image 

 prism, but without finding any traces of polarization in its 

 light. 



VELOCITY OF METEORIC STONES. 



Professor John le Conte, of the University of California, 

 communicates to Nature an article upon the maximum veloc- 

 ity of meteoric stones on reaching the surface of the earth, in 

 which he adverts to the statement of Nordenskjold, that me- 

 teoric stones, weighing two pounds each, fell on the ice of a 

 certain lake in Sweden, and failed to penetrate, making holes 

 only three or four inches deep in the ice, and rebounding. 

 This slight velocity, however, he shows, by a careful calcula- 

 tion, to be entirely normal, and the result of the resistance of 

 the air, and not to be in any measure an indication of the ve- 

 locity which they had when entering the atmosphere. In 

 the cases of small stones, the professor states that the resist- 

 ance of the medium would very speedily produce retarded 

 motion, and before traversing twenty or thirty miles of air 

 they would probably move with a velocity approximating 

 uniformity, and under the action of gravity alone. In other 

 words, they would gradually lose their original velocity of 

 translation, and, descending nearly or quite vertically, under 

 the action of gravity, would ultimately attain a maximum 

 velocity, under the opposing influences of the resisting and 

 accelerating forces, and then descend to the earth with a uni- 

 form velocity. 



lie thinks, however, the case would be different in propor- 

 tion as the mass is greater. 12 A, September 14, 18 VI, 398. 



