448 MOSsoTTi ON fraunhofer's reticular spectra. 



the true one. By this method I obtained for the maximum of 

 the intensity of the light, 



Xm = 0-02255; log ^,„ = 7-84253 ; A,„ - X^ = 16-96; 

 whence, X^ being = 553-5, we have 

 \,n = 570-5. 

 By the formula (1.) x = 3' 4" = 184" corresponds to this value 

 of X,„, so that as the interval DE = 11' 50" = 710", and conse- 

 quently ^ DE = l77"-5, i DE = 236"-7 ; we see that the place 

 found for the maximum of the intensity of the light in the 

 prismatic spectrum falls at one-fourth or one-third of the interval 

 DE, as required by experiment. 



7. Xm having the value obtained by the formula (8.), we have 



r,„ = 0-978. 

 If in the equation (4.) we make G = ], it should be verified 

 by this value of r„, ; whence 



ax ; 



and if the calculation be carried out, we find 

 log ?i = 4-28391. 

 This value of n is necessary, in order to pass from the value 

 of /' in the case of the reticular spectrum to that of G, corre- 

 sponding to the prismatic spectrum, if we indicate as unity the 

 maximum of the intensity of the light in each spectrum*. 



8. To ascertain whether the assumed formula (6.) also ful- 

 fills the second condition, i. e. represents the intensity of the 

 light at diiferent points of the prismatic spectrum near the 

 principal lines, we have first to deduce from the same formula 

 the values of r, which correspond to the values of X belonging 

 to these lines; and then from these values, by means of the 

 formula (4.), those of G. 



Fig. 1, Plate II., represents the curve given by equation (6.), 

 presupposing that in this equation instead oi ^ i^^ expression (8.) 

 was substituted, and r indicates the ordinates and ~ the abscissce, 



* If it were required to fulfill the condition that both spectra should contain the 



same amount of light, n must be determined by means of the formula n = >-pq— ,- , 

 * ■' J \j a X 



and therefore the value of the intensity G obtained from our formula must be 



divided by this value of « ; but in this case the maximum intensity G would no 



longer be expressed by unity. 



