MOSSOTTl ON FRAUNHOFER's RETICULAR SPECTRA. 449 



counted from the axis jw, and measured in parts of the semi-cir- 

 cumference. I first took on this curve, which was drawn in cor- 

 rect proportions, the nearest values of F, corresponding to the 

 values belonging to the lines B, C, D, E, F, G, H, and then 

 corrected these values, so that they accurately satisfied the equa- 

 tion (6.) ; thus I found 



From these values of A fi'om that of w, and from the values of 

 -z — already calculated, I then deduced by means of formula (4.) 



W A 



These values of the intensities of the light of the prismatic 

 spectrum, arising from the laws expressed by ti.e formulae (1.) 

 and (6.), all lie between those given by observation which are 

 detailed in No. 4 ; and they therefore show that the formula 

 assumed is capable of representing the phaenomena. In fact, 

 the limits between which the data of the observations detailed 

 range, show how difficult is the determination of these data, and 

 consequently what uncertainty still remains regarding their va- 

 lues. Thus the necessity of philosophers discovering photome- 

 tric means which are susceptible of greater accuracy, becomes 

 more and more striking. For want of more accurate data, we 

 consider it superfluous to ascertain whether, by an alteration in 

 the formulae, or rather of their coefficients, a greater ajiproxima- 

 tion of the calculated to the observed results could not be attained. 



§ IV. Remarks. 



9. The values of z and F in the formuUe (7.) and (8.) are so 

 expressed that the intensity of the light in the centre of the nor- 

 mal spectrum is at a maximum, when F is equal to the radius or 

 unity, and the abscissae increase proportionally in parts of the 



mi-circumference tt. 

 lium formula (7.) 



~-l 



VOL. V. I'ART XIX. 



If \ be taken as 



have 



2 II 



