to the Antarctic Regions. 217 



that of its elevation in the other, are to be carefully noted. The sum 

 of the two is the height of a column of water which the wind is ca- 

 pable of sustaining at the time, and every body that is opposed to 

 that wind will be pressed upon by a force equivalent to the weight 

 of a column of water, having its base equal to the surface that is 

 opposed, and its height equal to the altitude of the column of water 

 sustained by the wind in the wind-gauge. 



The height of this column being given, the force of the wind on 

 a foot square is easily found by a table which will be given in the 

 appendix. 



The observation of the gauge should always be made at the same 

 point of a free space, and in gusty weather the maximum of the os- 

 cillation recorded. The most proper periods will be those of the 

 other regular observations; but in great storms, or under other par- 

 ticular circumstances, occasional observations should be made, and 

 registered apart. 



Even in observatories which are provided with Osier's apparatus 

 it is desirable that an accurate comparison should be made of the 

 two anemometers. 



The points most important to remark respecting the wind are, 



1st. Its average intensity and general direction during the several 

 portions of the day devoted to observation. 



2ndly. The hours of the day or night when it commences to blow 

 from a calm, or subsides into one from a breeze. 



Srdly. The hours at which any remarkable changes of its direc- 

 tion take place. 



4thly. The course which it takes in veering, and the quarter in 

 which it ultimately settles. 



5thly. The usual course of periodical winds, or such as remark- 

 ably prevail during certain seasons, with the law of their diurnal 

 progress, both as to direction and intensity ; at what hours, and by 

 what degrees they commence, attain their maximum, and subside ; 

 and through what points of the compass they run in so doing. 



6thly. The existence of crossing currents at different heights in 

 the atmosphere, as indicated by the courses of the clouds in different 

 strata. 



Tthly. The times of setting-in of remarkably hot or cold winds, 

 the quarters from which they come, and their courses, as connected 

 witli the progressive changes in their temperature. 



8thly. The connexion of rainy, cloudy or fair weather, with the 

 quarter from which the wind blows, or has blown for some time pre- 

 viously. 



The Rain-gauge may be of very simple construction. A cubical 

 box of strong tin or zinc, exactly 10 inches by the side, open above, 

 receives at an inch below its edge a funnel, sloping to a small hole 

 in the centre. On one of the lateral edges of the box, close to the 

 top of the cavity, is soldered a short pipe, in which a cork is fitted. 

 The whole should be well painted. The water which enters this 

 gauge is poured through the short tube into a cylindrical glass ves- 

 sel, graduated to cubic inches and fifths of cubic inches. Hence 



