1870.] Observations in India, 231 



appears that while the radiation at both stations increases from 8 a.m. and 

 4 p.m. towards some time about noon, the difference M — D diminishes. 

 In other words, the radiation at the lower station increases more rapidly 

 than at the upper ; and while at both stations the change is more rapid 

 in the afternoon than in the forenoon, the relative change between forenoon 

 and afternoon is greatest at the lower station. 



(17) Mr. Hodgkinson, in his paper already referred to, quotes certain 

 numbers obtained by Principal Forbes from his " free hand curve " of ob- 

 servations on the Faulhorn and Brienz, showing the relative intensity of 



. F 



the two stations. Calling his ratio the following may be contrasted : — 



By Mr. Forbes. From Table III., Nov. 4th, 1869. 



u F , 



Hour. h m s jj • 



8 8 15 1-174 



9 1141 9 11 23 1-146 



10 1-214 10 8 45 i"i37 



1 1 i'345 11 H 22 i'°97 



12 1*219 080 i"o.8i 



1 1*078 1 8 45 vjoi 



2 1-207 2 10 3° 1*141 



3 1-217 3 9 3° 1 202 



480 I- 4 2 9 



where the heights of the stations are : 

 feet 



Faulhorn 8747 



feet 



„ > by Principal Forbes. 

 Brienz 1903 J * 



Mussoorie .... 6937 1 from the records of the Great Trigonometrical 



Dehra 2229 J Survey of India. 



In conclusion I gladly acknowledge that I am much indebted to my 

 friend Mr. Cole, not only for his skill and industry in taking the obser- 

 vations at Dehra, but for his cordial cooperation in reducing and discussing 

 them. 



Hoping you continue in the enjoyment of good health, I am, dear Sir, 

 with kind wishes, 



Yours very truly, 



J. H. N. Hennessey. 



General Sir Edward Sabine, K.O.B., $-c, 

 Pres. Roy. Soc., London. 



The record of actinometer observations has been posted in a separate 

 packet *. The papers enclosed with this letter are the paper of actinome- 

 tric curves and the result-abstract Table. 



[ * This record is preserved in the Archives for reference. — G. G. S.] 



