80 



KEPORT OF THE SECRETARY. 



ferent clnys. This arbitrary methcMi of reduction is necessary, for differences 

 of atmosplieric transparency and differences of solar distance make a direct 

 comparison of one observational curve with another complicated and unsatis- 

 factory. 



Plate VI shows two of the solar curves plotted with abscisste as air-masses 

 derived on the above assumptions, and ordinates as the logarithmic deflections. 



The general absorption of the solar envelope appears to be like that of the 

 earth's atmosphere, greatest at the violet end of the spectrum. This is shown, 

 and also some of the changes which have been noted in the apparent solar trans- 

 mission, in Table 3. 



In this table the numbers purport to represent the percentage transmission of 

 the solar envelope for vertical rays, on different days, and for various rays 

 between wave lengths OAu in the violet, and 2.0/i in the infra-red. The results 

 are based on the assumptions stated above, and a considerable dift'erence will be 

 noted from the corresponding table of last year, owing to a change in the 

 assumed thickness of the absorbing envelope. 



Table 3. — Transmission of sOlur envelope. 



Wave length . 



0.40 



0.45 



0.50 



0.60 



1^ 

 0.70 



0.80 



0.90 



ft 

 1.00 



1.20 



1.60 



2.00 







Date. 







Co 



efliciei 



its for 



vertica 



1 transmission. 





1903. 





0.445 



.510 



(.440) 



0. 495 



.560 

 .495 



0.585 



.640 

 . 575 



0. 635 



.690 

 .685 



0.675 



.7:*) 



(.660) 

 .69 

 .695 

 .700 

 .690 



.710 



.705 

 .705 

 .685 

 .695 

 .6a5 

 .695 



0. 700 

 .750 



0.715 

 .770 



0.740 

 .800 



0.790 

 .830 



0.830 



1904. 





(.850) 













.71 



.725 



.73 

 .745 



.76 

 .770 



.80 

 .810 



.835 



December 6 







(.53) 

 .525 

 .525 



.545 



.540 

 .540 

 .530 

 .5.30 



.615 

 .605 



(.600) 



.625 

 .620 

 .620 

 .610 

 (.610) 



.665 

 .660 

 .655 



.680 

 .670 

 .670 

 .655 

 (.660) 





December 8 





.475 



.475 



.840 







.835 



i9a5. 





.735 



.730 

 .730 

 .710 

 .720 



.750 

 .745 

 .745 

 .720 

 (.740) 



.775 



.770 

 .770 



(.805) 

 (.805) 

 (.805) 



.840 









.840 









.840 







.475 

 .475 





February 14. 



(0.415) 





(.810) 



.840 

 .840 





.450 



.480 

 .480 

 .480 

 .480 



.480 

 .480 



.530 

 .530 

 .530 

 .530 

 .530 

 .530 

 .525 

 ..530 

 .525 

 .525 

 .530 

 .530 



(.610) 



.665 



.715 



(.7a5) 







.840 











March 16 





.605 

 .6a5 

 .605 

 .605 

 .605 

 .605 

 .605 

 .600 



.660 

 .660 

 .660 

 .660 

 .650 

 .650 

 .655 

 .655 



.690 

 .690 

 .690 

 .690 

 .680 

 .680 

 .690 

 .690 



.710 

 .710 

 .710 

 .710 



.730 

 .730 

 . 730 

 .730 



.760 

 .760 

 .760 

 .760 



.795 

 .795 

 .795 

 .795 



.830 



March 18 





.830 



March 26 





.830 



March 31 -J 



.830 







April 25 ' - . 



.465 

 .475 

 .475 

 .490 

 .490 

 (.465) 

 (.460) 













May2 



May20 



.48? 

 .48? 

 .450 

 .450 













.710 



.730 



.760 



.800 



.830 



June 9 - 



June 17 



.620 



.670 



.710 



.725 



.740 



.765 



.810 



.845 



June 19 . . - . - - 



.510 

 .505 

 .525 

 .525 

 .520 



.590 

 .590 

 .595 



.640 

 .640 

 .640 



.670 

 .680 



.700 



.720 



.755 



.795 



.830 



June 22 









, 















June 28 

























.600 



.6.50 



.685 

























