712 



Reviews. 



[Oct., 



however, produces 47 times the effect of a whole atmosphere of air, 

 while to of an atmosphere of the latter produces 612 times the effect of 

 a whole atmosphere of air. Eeducing dry air to the pressure of the 

 acetic ether here employed, and comparing them then together, the 

 quantity of wave motion intercepted by the latter would be many 

 thousand times that intercepted by the air. 



"Any one of these vapours discharged in the free atmosphere in 

 front of a body emitting obscure rays, intercepts more or less of the 

 radiation. A similar effect is produced by perfumes diffused in the 

 air, though their attenuation is known to be almost infinite. Carrying, 

 for example, a current of dry air over bibulous paper moistened by 

 patchouli, the scent taken up by the current absorbs thirty times the 

 quantity of heat intercepted by the air which carries it, and yet patch- 

 ouli acts more feebly on radiant heat than any other perfume yet 

 examined. Here follow the results obtained with various essential 

 oils, the odour in each case being carried by a current of dry air into 

 the tube already employed for gases and vapours : — 



Name of Perfume. 













Absorption 



Patchouli 30 



Sandalwood . 













32 



Geranium 













33 



Oil of cloves 













34 



Otto of roses 













37 



Bergamot 













44 



Neroli < 















47 



Lavender 















60 



Lemon , 















65 



Portugal 















67 



Thyme 















68 



Rosemary 















74 



Oil of laurel , 













80 



Camomile flowers 













87 



Cassia 













. 109 



Spikenard . 













. 355 



Aniseed 











. 372 



bsorption 1 



jy a 



tube 



fuU 



of d 



ry ai 



v bei 



ng 1, th 



odour of patchouli diffused in it is 30 ; that of lavender 60, that of 

 rosemary 74, whilst that of aniseed amounts to 372. It would be idle 

 to speculate on the quantities of matter concerned in these actions." 



It would be impossible, in a short notice such as the present, to 

 refer to the numerous and interesting results that have been obtained 

 by experimenting upon the passage of heat through the atmosphere, 

 or in vacuo. Dr. Tyndall has tested the absorbing and analyzing 

 powers of numerous substances, and in some cases has applied his 

 experiments to practical ends, or at least he has indicated channels in 

 which they may be practically employed. Thus he has tested, physically 

 and chemically, the percentage of carbonic acid in the human breath, 

 and when we remember what startling and unexpected results have 

 recently been obtained by means of spectrum-analysis ; how, for ex- 

 ample, blood has been traced in fabrics long after the tell-tale fluid 

 was spilt upon them, we cannot but watch with interest, researches 

 which have a direct bearing upon physiological and sanitary science. 



