230 PHENOMENA CONNECTED WITH CLOUDY CONDENSATION. 



breathing. This effect is, of course, greatest when the windows are 

 unprotected by blinds, shutters, or curtains. It is evident that, tliough 

 a window may snpply pure air when it is open, it yet does nuicli harm 

 when closed by bringing down the impure air, which, if undisturbed, 

 would have a less injurious effect. 



It is to be regretted that this investigation does not promise to yield 

 mucli of ])ractical valne; nevertheless, as we cultivate not only frnits 

 but Howers, so, for the same reason that we cultivate the latter, it is 

 thought that these exj)eriments will repay the attention of physicists. 

 The colors produced by such simi)le materials as a little dust and a 

 little vapor are as beautiful as anything seen in nature, and well rci)ay 

 the trouble of re-i»roducing them. 



