On Solar Radiation. 



195 



" When a series is long continued in a good sun, the in- 

 strument grows very hot, and the use of the liquid in the sun 

 observation decreases, while the fall in the shade increases ; 

 nay, towards sunset it will fall even in the sun. This phe- 

 nomenon (which is at first startling, and seeming to impeach 

 the fidelity of the instrument) is, in fact, perfectly in order, 

 and produces absolutely irregularity in the resulting march 

 of the radiation. Only it is necessary in casting up the result 

 (in col. 5) to attend carefully to the algebraic signs of the 

 differences in column 4, as in the following example, (which 

 as well as that above given, is one of actual occurrence). 



6. 

 Remarks. 



Alt. of 0=70 191. 



Cirrus haze coming on. 

 Alt. of = 40 37/. 



iri -ajBOs jo KjiBd ui uorreip^ 







11.25 

 9.25 

 8.20 







•a^nuim aad aSu^qg 





r- CN co to O 

 O CN oi — < Tji 



+ 7 i 7 i 





3. 



Readings of the In- 

 strument. 



•a 



a 



« 



+ 9.7 



10.8 



31.4 



17.0 



8.0 





.•a 



a 

 i— i 





+ 9.9 

 23.0 

 34.0 

 28.5 

 12.0 





•ap^qs 

 ^ 10 uns ainsodxg 





© + © + © : 





1. 



Date and times of ob- 

 servation, Wynberg, 

 Nov. 24, 1837. 



-i 



a 

 'a 





o o o o o ' 



CJ CO ■ 

 O — i CO ■* o 





Initial. 



H. M. S. 



6 5 15 



9 



10 30 



12 



13 30 

 15 



6 19 15 



