170 Scientific Intellic/ence — Meteorology. 



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not having been obtained as yet, there remains only the three first 

 by which the theory can be tested. 



In a preliminary calculation which we have instituted, we do not 

 find the results so accordant as we had been led to expect, but 

 still sufficiently so to give a certain probability of the approach to 

 truth, in a case where the quantity had not been observed. 



Viewed in this light, some very interesting results are obtained. 



1st, The idea entertained by Bianchini and other observers, that 

 the rotation of Venus is nearly 24 times as long as hitherto sup- 

 posed, is utterly untenable. 



2d, The time of rotation of Uranus, a quantity never yet observed 

 (but doubtless capable of being observed by a telescope of Lord 

 Rosse's calibre, removed to a table-land in a tropical country^ is 

 given ; and appears so very different from any other yet observed, 

 especially so from those of its neighbours Saturn and Jupiter, be- 

 ing = 1-396779, earth's = 0-997270 (sidereal rotation in mean 

 solar days.) 



3c?, Knowing the rotations of Jupiter and Mars, we may supply, 

 by using the analogy conversely, the diameters of their spheres of 

 attraction, and thus get at the elements of the lost planet between Mars 

 and Jupiter, and these appears to be; — mean distance = 2* 90851 11 

 (earth unity), mass in terms of Sun yss^ii^^oj sidereal rotation m 

 earth's mean solar days 2-406104, and diameter of sphere of attrac- 

 tion 0-830951, in terms of earth's distance. The size is thus a little 

 larger than Mars. The slowness of rotation is remarkable, especially 

 in the case of a planet which is supposed since to have burst into 

 pieces : the Americans have called it Kirkwood. 



P. S. 



SCIENTIFIC INTELLIGENCE. 



METEOROLOGY. 



1. Use of Coloured Glasses to assist the View in Fogs. — M. 

 Lavini of Turin, in a letter to the editor of Vlnstitut at Paris, makes 

 the following curious observation, which, if confirmed, may prove to 

 be of great importance : — *' When there is a fog between two corres- 

 ponding stations, so that the one station can with difficulty be seen 

 from the other, if the observer passes a coloured glass between his 

 eye and the eye-piece of his telescope, the effect of the fog is very 

 sensibly diminished, so that frequently the signals from the other 

 station can be very plainly perceived ; when, without the coloured 

 glass, even the station itself is invisible. The different colours do 

 not all produce this effect in the same degree, the red seeming to b6 

 the best. Those who have good sight prefer the dark-red, while 



