.^ 



f 



% 



^T^^-^ 



s 



I 



28< 



> 



METEOROLOGY. 



[Sect IX. 



100 inches of the graduated vessel, and a thousandth 

 of an inch may easily be read off. It is very difficult to 

 place the rain-gauge properly on shipboard, and its 

 entries therefore require constant explanatory notes, 

 pointing out causes tending to disturb its influence. In 



fact, exceptin 



( 



it seems hardly possible to devise a tolerably permanent 



situation for it, O 



the 



a perfectly open exposure 



on 



chosen. 



ground, or veri/ little elevated above it, should be 

 ■ The quantity of water should be daily mea- 

 sured and registered at 9 a.m., unless the fall of rain be 

 so heavy as to endanger filling the instrument witlun the 

 24 hours, when this operation should be performed as 

 often as needed. Snow collected or water frozen in the 

 reservoir should be melted. 



The Anemometer. — Lind's would appear to b-- the only 

 anemometer which can conveniently be used on shipboard. 

 It is adjusted by filling it with water till the liquid in both 

 legs of the syphon corresponds with zero of the scale. It 



is to be held perpendicularly with the mouth of the kneed 

 tube turned towards the wind, and the amount of depres- 

 sion in the one leg and of elevation in the other are to be 

 noted. The sum of the two is the height of the column of 

 water which the pressure of the wind is able to support : 

 and the force of the wind on a square foot is obtained 

 from this L.ight by Table IV. of the Appendix. In great 

 degi*ees of cold a saturated brine may be used which does 

 not freeze, and whose specific gravity being 1 '244, the 

 force given by the table must be multiplied by this 

 factor. In addition to the regular hours of observation 

 this instrument should be observed in storms, white 



i 



S<=^ * 



^1 



4b, 



of ^' ' 



e 



T 



slieet ■•■ 



>■" 



^ 



Ui 



. 1 A 



'^10* 



dii'ectic] 



-L _ ^ -"^ 



ifr-£^ *■ 



.) 



it I 



t., ;i.ii.lU 



Ivtli 



} 



The. 



oated : 



of tk> 



* I 



cemenl.. 



1 ''^^ 





JX 



-^ 



of 



1 



Jx . 



* - 



-• ar. : 



wrench 

 The J 



a spirit ; 



ver^ 1 



(>ij 





tur^ 



the- , 



^it 



^^feT>4 : 



1 



