NATURAL PHILOSOPHY. 185 



ent degrees of violence. They would thus be propagated with different 

 degrees of rapidity, and would therefore not fall upon the ear, if it were at 

 any distance off, with a sudden crash, but in a series of minor claps, or as a 

 rattle. If this theory be true, the report of a cannon should travel faster 

 than the human voice, and that of thunder faster than either. London 

 Photographic News. 



C HROMO-T YPOG RAPH Y. 



M. Rochette has devised a new method of printing the different colors used 

 in this art. Instead of applying a series of plates or stones, each bearing 

 one color, in the usual way, he arranges his plates upon a rotating platform, 

 of smaller dimensions, but like those used on railways. Suppose four plates 

 thus arranged with black, red, blue, and green, and a sheet of four pages, 

 which it is desired to print, imposed upon them. One page will be printed 

 in each color, and by turning the sheet a quarter round each time, the 

 remaining colors will be printed in succession. This apparatus has a me- 

 chanical contrivance to ensure accuracy of position; and, as the colors 

 admit of super-position, green may be formed by successive printings of 

 yellow and blue, orange by yellow and red, etc. 



ON THE SOLUTION OF ICE IN INLAND WATERS. 



In a paper read before the American Association for 1860, by Mr. B. F. 

 Harrison, a theory to account for the sudden disappearance of ice in inland 

 waters was presented, which was based upon a series of observations made 

 upon a little lake in Connecticut, which is so hedged in that only the south 

 and southwest winds blow upon it. It is not fed by any large stream, and 

 has a small outlet. On the twenty-third day of January, I860, he visited the 

 lake, and found the ice ten or eleven inches thick. He found, at a station on 

 the lake, the temperature of the water directly under the ice to be thirty -four 

 degrees; three feet down, thirty-eight; twelve feet, forty-one ; the bottom of 

 the lake, forty-three and a half; mean temperature, thirty-eight and seven- 

 eighths. On the sixth of March he found the ice disappearing very rapidly, 

 as much as one-third disappearing during the two hours that he remained 

 by the lake. The mean temperature of the lake on this date was forty-one 

 and a half. The conclusion arrived at was, that the solution of the ice is 

 caused by heating up the water from the bottom, since the warmth could 

 not have been communicated from the atmosphere, its temperature being 

 lower than the water. The mean temperature of the earth at a depth of 

 twenty feet furnishes a vast magazine of heat, that is immediately effective 

 as soon as the cold from the atmosphere ceases to be intense. 



THE GREAT PYRAMID. WHY, AND WHEN, WAS IT BUILT? 



The above is the title of a volume recently published in London by John 

 Taylor, a gentleman of an exceedingly original mind, and favorably known 

 in literary and scientific circles. His researches and speculations, whether 

 leading to any truthful result or no, will at least be found interesting and 

 curious : 



Of all the records of their existence, which the men of ages long gone 

 by have left upon the face of the earth, none, perhaps, is so eminenth r calcu- 

 lated to excite universal interest, or to give rise to enthusiastic speculation, 



16* 



