to the Antarctic Regions. 209 



oljservatlon 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 all 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. 



Having previously ascertained how many times (suppose 20) the 

 watch beats in five seconds, let the screen be withdrawn at ten seconds 

 before a complete minute shown by the watch, suppose at 2'' 14-"* 

 ,W^. From 5& 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 minute, 2^ 15™ 0^, keeping the 

 eye not on the watch, but on the end of the rising column of liquid. 

 At the 20th beat read off, and register the reading (12°'0), as in co- 

 lumn 3, A, of the annexed form. Then wait, watching the column 



of air above the liquid, to see that no blebs of liquid are in it, or at 

 the opening of the upper bulb (which will cause the movement of 

 the ascending column to be performed by starts), till the minute is 

 nearly elapsed. At the 50th second begin to watch the liquid rising ; 

 at 55^ begin to count 0, 1,2, up to 20 beats, as before, attentively 

 watching the rise of the liquid ; and at the 20th beat, or complete 

 minute (2^* 16°* 0^) read off, and instantly shade the instrument, or 

 withdraw it just out of the sun and penumbra. Then register the 

 reading off ( 4-3°3) in column 3, B, and prepare for the shade obser- 

 vation. All this may be done without hurry in 20 seconds, with time 

 also to withdraw the screw if the end of the column be inconveniently 

 high in the scale, which is often required. At the 20th second pre- 

 pare to observe ; at the 25th begin to count beats, 0, 1 , 2, .... 20 ; 

 and at the 20th beat, i. e. at 2** 16" 30S read off, and enter the read- 

 ing in column 3, A, as the initial shade reading (45°*2). Then wait 

 as before till nearly a minute has elapsed, and at 2^ 17°* 20* again 

 prepare. At 17"* 25* begin to count beats ; at 1 7"* 30* read off, and 

 enter this terminal shade reading (42°'8) in column 3, B, and if 

 needed, withdraw the zero. 



Phil. Mag. IS. 3. Vol. 15. No. 95. Sept. 1839. P 



