MODERN SUN CULT — STURMER 205 



to US filtered by the atmosphere. It is also more intense. For these 

 reasons the radiation artificially produced is far more dangerous. 

 But unquestionably, tiie contrivances to furnish ultra-violet and thus 

 to compensate for our loss of normal sunshine, are, if used properly, 

 of proat value. It is not wise, however, to proceed to self-treatment 

 without expert direction. Here also conservatism is the part of wis- 

 dom. Let those who have been specially trained, do the pioneering. 



THE ZONES OF ULTRA-VIOLET RAYS 



The radiation from a mercury vapor lamp produces violet, blue, 

 •rreen, and yellow li^ht waves, which can be filtered out; and also 

 ultra-violet rays from the violet down to a wave length of about 1,850 

 to 1,870 A. Waves shorter than 1.850 A are cut out by quartz and are 

 never found in the radiation from a mercury vapor lamp. The waves 

 of the Dorno region, 2,900 to 3,130 A, and the longer ones, have the 

 action of sunlight, but are of course supplied in greater abiuidance. 

 Like sunlight they stimulate metabolism, govern our calcium balance, 

 increase the alkalinity and the iron content of the blood, sharpen the 

 appetite, and may be used in the treatment of rickets, certain skin 

 diseases, and of tuberculosis. Such skin irradiation produces a slight 

 rise in the temperature, which soon falls to normal. It does not af- 

 fect the blood pressure. If prolonged, it can, of course, cause sun- 

 burn, and it may cause inflammation of the eyes, this being due mainly 

 to the waves shorter than about 3,050 A. 



Waves shorter than 3,000 A are correspondingly more irritating 

 and more dangerous to the eyes. Since these shorter waves are pro- 

 duced in the operation of electric welding, they are frequently en- 

 countered, and their dangerous nature should be kept in mind. 

 Goggles of special glass designed to intercept them, are worn by the 

 persons engaged in such operations; the spectators, however, are not 

 so protected, and must look out for themselves. 



BACTERICIDAL RAYS 



The waves shorter than 3,000 A and longer than 2,000 A are de- 

 cidedly bactericidal, particularly those between 2,490 A to 2,380 A. 

 But longer wave-lengths also have a killing effect on some germs, 

 though in a much lesser degree. Indeed, this is true in a measure in 

 regard to the violet, the blue, and the green of the visible spectrum. 

 Speaking generally, the longer the wave lengths, above 3,000 A, the 

 less effective are the rays in the destruction of bacteria. 



CHEMICAL ACTION 



Waves shorter than 3,000 A also convert oxygen into ozone, hence 



this substance is always in evidence when an ultra-violet lamp is in 



operation. Ozone is a very active oxidizing agent, and in dilution 



acts on us as a stimulant. It is interesting in this connection to note 



