B. TERRESTRIAL PHYSICS AND METEOROLOGY. 85 



or backward, according as the ivory float rises or falls. The 

 movements of the clock-work are followed by a pencil which 

 draws a curve upon a revolving cylinder. In a very similar 

 instrument devised by Professor G. "VV. Hough, of Albany, 

 and highly prized by American meteorologists, the connection 

 between the horizontal lever and the wheel-work is an elec- 

 tric one, and subject therefore to all the uncertainties of the 

 electrical batteries and connections. In Redier's barometer 

 no electricity is employed, the entire apparatus depending 

 only upon gravity and atmospheric pressure, and its working 

 is evidently perfectly regular and reliable. An aneroid ba- 

 rometer may be made to record its indications in the same 

 manner as the mercurial, and such instruments have, we un- 

 derstand, already been constructed under Mr. Redier's direc- 

 tions. Mr. Silberman has suggested a method by which a 

 similar automatic system of registration could be applied to 

 the indications of the magnetic needle. JYoiivelks Meteor o- 

 logiques, 1875, p. 16. 



CURRENTS OF AIR WITHIN CYCLONES AND WATERSPOUTS. 



In a memoir on cyclones and waterspouts, Mouchez pub- 

 lishes some observations made by him while upon the ocean, 

 and which, if correct, are quite important. According to 

 him, at or near the surface of the ground the movement of 

 air in the cyclone is always from below upward, while in 

 whirlwinds the movement is, on the contrary, from above 

 downward. In the former case the winds are winds of as- 

 piration ; in the latter case the wind descends from the 

 cloud in the form of a bag or tube, which terminates in a 

 point. He believes that waterspouts have no relation what- 

 ever to cyclones, having an opposite appearance and cause. 

 In this opinion Renou also concurs. JYbuvelles Meteorolo- 

 (/iques, 1874. 



THE PROGRESSIVE MOVEMENT OF AREAS OF COLD AIR. 



Dove has attempted to deduce, from the five-day means 

 of temperature for European stations, some general views as 

 to the progress of days of remarkable cold, and finds that in 

 the months of January and February of the years 1855, 1856, 

 1870, and 1871, numerous cases occurred to show, almost uni- 

 formly, that the " cold terms " move westward over Europe ; 



