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Physics and Chemistry. 409 
of sodium mixed with sesquichlorid of iron. The author recommends a 
solution containing two parts of this nitro-prussid, two of dry sesqu 
chlorid of iron, and ten of water. The solution is to be filtered and kept 
judge of its value——Zes Mondes, March, 1864, 415. W. G. 
. rometer, as an indicator of the earth’s rotation, and the 
sun's distance ;' by Pi ARLE Crase.—The existence of daily baro- 
ey occur in all cl , and at all ons; 3, opposite effects are 
ced at different times, under the same average temperature. Thus 
at St. Helena, the mea hree years’ hourly observation gives the fol- 
lowing average barometric heights : 
From Ob to 12h 28-2801 in. From 185 to 64 28-2838 in. 
“ 12h to oh 28-2861 « “ 64 to 18h 282784 “ 
The upper lines evidently embrace the coolest parts of the day, and 
in warmest, Dividing the day in the first method, the 
former to the latter is ,-2 95.5, 0r 00109. This ratio represents the 
ttlonate elevation or depression of the barometer above or below its 
Mean height that should be caused by the earth’s rotation, and it corres- 
»s Very nearly with the actual disturbance at stations near the equator, 
From Oh. to 6h. the air has a forward motion greater than that of the 
farth, so that it tends to fly away ; its pressure is therefore diminished, 
8 greatest ; 
; Pp an arometer rises, 
rit 12h. to 18h. the earth moves away from the air, and the barometer 
.) While from 18h. to 24h. the increasing velocity of the air urges it 
gage € earth, and the barometer rises. : 
From the Proceedings of the American Philosophical Society. 
AX. Journ, one Series, Vou. XXXVII, No. 111.—Mar, 1864 
