SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 87 



EXPLANATION OF FIGURE 1 



Upper Section : ABSORPTION. 



a Water, ultra-violet, visible, and infra-red. 



Ordinates : Absorption coefficients k in I =1 hc'^'^ (outside left). 



Thickness transmitting half intensity in cm (inside left) 

 Transmission of i-cm thickness (right). 

 Abscissae: Wave lengths in microns pl (bottom). 

 Wave numbers, waves per cm (top). 



b Water, X ray (same ordinates). 



Wave lengths in Angstroms (instead of /i as indicated 



at bottom). 



c ._._._._ Ozone, (same coordinates as in a; gas at standard conditions). 



Atmospheric transmission is equivalent to about 3 mm and can be 



found by shifting scale (right) up by approximately half a 



division. 



Middle Section: RADIATION. 



Relative emission from body at 1,000° K. (dull-red therapeutic lamp). 

 Relative emission from body at 3,000° K. (high-temperature Tungsten 



lamp). 

 Relative emission from sun. 

 Relative emission from mercury arc in (|uartz. 



Lower Section: BIOLOGICAL PHENOMENA. 



a, transmission of flesh (1/2 cm thick) in per cent. 



b, relative visibility. 



c, relative phototropism. 



d, Vitamin A. 



Absorption and vitamin value disappears when radiated. 



e, Ergosterol. 



Absorption disappears under radiation, which produces activation 

 yielding therapeutic value of vitamin D. 

 /. Relative erythema effectiveness, zero degree (very light). For extreme 

 erythema, fourth or fifth degree, the relative intensities of the 

 the two maxima are reversed. 



