84 Prof. S. P. Langley or a Possible 
TABLE I." 
-- Atmospheric Transmission of Radiation for Zenith Sun. 
Pivehtel|el|eple | | | B | Bele 
Wave-length ...'0°40 |0°45 [0°50 |0°60 {0°70 |0-80 |0°90 | 1:0) a 16} 2-0 
} 
‘i Raa’ ne | 
Date. _ Percentage Transmission for Vertical Rays. 
} 
} 
1908. Feb. 1? | 67 | 64.| 66 | 72 | 76 | 80 | 83 | 85 | 86 | 90 | OB 
Mar. 3, | 48 60 | 66 | 68 | 74 | 83 | 88 | 90 | 93 | 93 | 92 
y Mare 32 | 40 | 48 | 66 | 73 | 79 | 84 | 87) 89 | 92 | 961 96 
7 ” 6. 47 dO 57 . } 
‘ eS ae ae |e | 80 | 
ee 55 | 60 | 69 | 7'| 80 | 82 | 87 | 90 | 94 | 97 | O7 
” ” : ° 8°¢ 5 . } > | 6 
» ye 7: | 46 | 49 | 56 | 66 | 72 | <6 | 77 | 80 | 83 | 88 | 90 
” fees 24. 42 | 60 | 66 | 69 | 77 | 82 | 85] & 
” a is. | 39 | 52 | 60 | 59 | 78 | 84 | 86 | 87 | 89 | 90 | 89 
” Aut 14, | 52 | 76 | 81 | 82 | 87 | 90 |.91 | 91 | 93 | 94 | OF 
" ie - | 641 70 | 76 80 | 85 | 88 | 89 | 91 | 91 |(92)/(92) 
52 | 59 me en ele | 85 | 88) 91 |(91) 
rar) 
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ot ieee, Se oe ar) ae ee Teen 89 92 93) 95 |(94) 
1804. S2n. a7, | 87 | ZL'| 75 | 80 | 86 | 89 | 90 | 91 | 92 | 94 194) 
- sae TT. | 89 | 87 | 73 | 73 | 79 | 84 | 89 | 91 | 91 /(91)}(91) 
" e " | 42 | 55 | 58 | 59 |'70 | 78 | 84 | 89 | 92 | 95 |(94) 
\ 
(e.°) 
—_ 
w 
_— 
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4 
_~ 
—* 
~ 
Mean Results. 
| 
| 
1903. Feb.-Aug. |47°5 /55°3 62:4 (68:2 75-6 '80°1 |82°9 [84-9 |87-6 90°8 [9-0 
1903-4. Sept.—Feb. |56°4 |66°3 72.0 |75°7 '81°6 '85°4 |88-0 |90-0 |91-4 93:1 |93-0 
1903-4. 51-2 598 65:2 |70°1 73-1 82-3 |85-0 |87-0 |89-2 |91'8 91-6 
1901-2. | ss. | «++ |76°5 [769 |85°7 89°7 |91-0 |92-1 |93°3 1930 [95-0 
/ | | ) 
temperatures, for if the air becomes more opaque, correspond- 
ingly less direct solar radiation remains in the beam to be 
absorbed at the earth’s surface, so that diminished surface- 
temperatures naturally follow. It is, of course, quite possible 
that in so complicated a thing as climate other factors may 
tend to reduce such direct effects, but these are not imme- 
diately apparent*. 
* An effect of diminished atmospheric trausparency upon plant-growth 
seems equally probable ; for it is generally conceded that certain functions 
of plant-growth depend on a supply of violet radiations. It will be seen 
that the defect of atmospheric transparency noted in the early months of 
1908 tended to reduce the intensity of the violet end of the spectrura 
most strongly. It would be of much interest to know if such a de- 
ficiency of violet rays may not have appreciably affected vegetation during 
this period. 
