568 Prof. C. V. Raman on the Scattering of 



for li = and h = 8, using the equation 



^=(D-tan-'D) S6C2D 



5 



\/WD-2* 



R' 



The error is always positive and limits the nse of the 

 formula (49) to small dips. 



Values of <p and D are interchangeable by means of 

 Table V. 



8. Effect of a Change of Density. 



Suppose the values of the observed density given in Table I. 

 are increased by 2 per cent. Then since the same increase 

 occurs in n , p, q, k, >sja, »Jb, v/c, the values of /\<p and A 2( £ 

 are increased by 2 per cent. Actual calculation shows that 

 the percentage changes in 7* and l { are small, except for 

 heights less than 2 km., when they may amount to an 

 increase of +1 per cent. This is so for <£ = 88°, while 

 for O = 9O O the changes do not exceed -5 per cent. Hence 

 the values of mi will not differ from the values in Table IV. 

 by more than 2 per cent. The formula? of § 6 show that the 

 changes in ei are inappreciable. The values of Q given 

 by (48) will increase in very much the same way as the 

 values of m, i. e. by not more than 2 per cent. This increase 

 will therefore be about +10 in the value of Q. But the 

 values of dQ obtained with the aid of (51), and used in 

 the calculation of Table VII., vary from — 88 to +100. 

 Hence the refraction errors in Table VII. overshadow changes 

 which are due to an increase of 2 per cent, in the density. 

 Note that for /^<4km. the density increase makes the error 

 in Chauvenet's formula less. 



LVI. The Scattering of Light in the Refractive Media of the 

 Eye. By C. V. Raman, M.A., Palit Professor of Physics 

 in the Calcutta University* . 



1. Introduction. 



IN his treatise on Physiological Optics f, Helmholtz has 

 discussed the explanation of the interesting phenomena 

 observed when a very small and intensely luminous source of 

 light is viewed directly by the eye against a dark background. 



* Communicated bv the Author. 



t Page 180, 1896 (German) Edition, 



