r:^ 



290 



METEOROLOGY. 



[Sect IX. 



the better. lie should have a watch or chrononicter 



beatine: at least twice in a 





concl 



^t;i;uiiuj and provided with a 



second hand ; also a pencil and paper ruled, according 

 to the form subjoined, for registering the observations. 

 Let him then grasp the instrument in his left hand, or, if 

 he have a proper stand (which is preferable on shore or 



m a 



buildin 



, othervvisc firmly support it, so as to 

 expose its face perpendicularly to the direct rays of the 



sun, as exactly as may be. 



The liquid, as soon as exposed, will mount rapidly in 

 the stem. It should be allowed to do so for a minute 

 before the observation begins, taking care, however, not 

 to let it mount into the bulb, by a proper use of the 

 screw. At the same time the tube should be carefully 

 cleared (by the same action) of all small broken portions 

 of liquid remaining in it, which should ail be drawn down 

 into the bulb. When all is ready for observation, draw 

 the liquid down to zero of its scale, gently and steadily ; 

 place it on its stand, with its screen before it, and proceed 

 as follows, first reading off the internal thermometer. 



Having previously ascertained how many times (sup- 

 pose 20) the watch beats in five seconds, let the screen 





withdrawn at ten seconds before a complete minute 

 shown by the watch, suppose at 2^ 14™ 50*. From 50' 

 to 55^ say 0, 0, 0, . . . . at each beat of the watch, 

 looking meanwhile that all is right. At 55' complete, 



count 



0, 1, 2, . . , . up 



to 



20 beats, or to the whole 





\ 



I 



h. 

 2 



4 





^. 



* This may consist of two deal boards, eighteen inches long, conBCcted 

 by a hinge, and kept at any required angle by an iron, pointed nt each 



The upper should have a little rabate or moulding fitting loosely 

 round the aetiaometer, to prevent its slipping off. 



end. 





i 



