24 Messrs. Nichols and Snow on the Character of 



the temperature rises. Suddenly, then, follows the outburst 

 of radiant energy which begins at the latter temperature. 



Table I. — Intensity of the Radiation from Platinum at various 

 Temperatures, in terms of the radiation of like wave-lengths 

 from an incandescent lamp. The intensity of the region 

 A. = '587 in the spectrum of platinum at 1000° is taken as 

 unity. 



Wave* 



lengths. 



1000°. 



950°. 



900°. 



850°. 



800°. 



750°. 



700°. 



650°. 



•713 



2-78 



202 



1-33 



•802 



•409 



•121 



•033 





•638 



1-56 



111 



•795 



•489 



•229 



•073 



•008 



•003 



•587 



1-00 



•725 



•482 



•253 



•101 



•035 



•005 





•544 



•659 



■479 



•316 



•174 



•059 



•010 



•002 





•oil 



•444 



•330 



•222 



•121 



•042 









•484 



•333 



•232 



•139 



•069 



•021 









•461 



•278 



•180 



•101 



•042 



•010 









•444 



•229 



•149 



•080 



•028 











•430 



•201 



•135 



•069 



•021 











Table II. — Intensity of the Radiation from the Oxide of Zinc 

 at various Temperatures, in terms of the radiation of like 

 wave-lengths from an incandescent lamp. The intensity of 

 the region X = *587 in the spectrum of glowing platinum at 

 1000° is taken as unity. 



Wave- 

 lengths. 



1038°. 



1013°. 



925°. 



884°. 



868°. 



848°. 



739°. 



707°. 



•713 

 •638 

 •587 

 •544 

 •511 

 •484 

 •461 

 •444 

 •430 



2-605 



2-778 

 2-504 

 1-880 

 2-013 



2-054 

 2-002 



3-026 

 1-985 

 2443 



2064 



i V 620 



1-332 

 •891 

 •659 

 •391 

 •565 

 •453 



'•420 

 •420 



•343 



•281 

 •278 

 •288 

 •283 

 •214 

 •179 

 •097 



'•313 



•235 

 •178 

 •190 

 •178 

 •160 

 •108 

 •093 



•708 







•250 

 



•221 

 •185 

 •188 

 •111 

 •091 



•084 

 •038 

 •019 

 •011 

 •010 

 •005 

 •003 



•034 



•013 



•007 



•003 



•0015 



•0008 



The character of the colour of the incandescent zinc oxide 

 can be given more explicit expression by means of isothermal 

 curves, in which the distribution of intensities throughout the 

 visible spectrum is shown for a given temperature, than in 

 those which have just been presented. Three ways of drawing 

 these curves offer themselves. The absolute distribution of 

 intensities may be given, the resulting curves being such 

 as would be obtained by exploring the spectrum with a 



