774 REPORT — 1898. 



lield in the hand is really due to the hydrocarbons to which this operation gives 

 rise ; and it is probable that no metallic particles, even in the form of vapour, 

 reach the nose or even leave the mf;tal. Hence, although smell may not, like 

 sound, he propagated by vibration, it seems probable that particles of the metal with 

 which we have been accustomed to associate tlie particular smell may no more 

 come into contact witli the olfactory nerves than a sounding musical instrument 

 strikes against the drum of the ear. 



And the same sort of result may occur when a metal is rubbed, for, although 

 in that case particles may very likely be detached, it seems possible that the 

 function of these metallic particles may be to act on the moisture of the air, and 

 liberate hydrogen simihirly contaminated; and that in this case also it is the 

 impurities whii-h produce the smell, and not the particles of the metal with which 

 we have been accustomed to associate it. 



This view I put forward tentatively ; nnd to further elucidate the matter I ain 

 about to begin a series of smell tests in various gases, artificially dried, with 

 metals as pure as can be obtained. 



1 next come to the diffusion of smell. From the experience we have of the 

 considerable distance at which a good nose can detect a smell, and the quickness 

 with which the opening of a bottle of scent, for example, can be detected at a 

 distance, I imagined that tubes not less than lo or 20 feet in length would be 

 required for ascertaining, even roughly, the velocity at which a smell travels. 

 Tiut experiment soon showed that when the sppce through which a smell had to 

 pass was screened from draughts, it diffused with surprising slowness, and that 

 feet could be replaced by inches in deciding on the lengths of the tubes to be used. 

 These are made of glass, which is relatively easy to free from remanent smells. 



When the room and tube had been freed from smell by strong currents of air 

 blown through them, the tube was corked up at one end and taken outside to have 

 another cork, to which was attached some odoriferous substance, inserted at the 

 other end. The tube was now brought hack to the odourless room, and placed in 

 a fixed horizontal or vertical position, and the unscented stopper was withdrawn. 

 As a rule, immediately after the removal of the stopper, a smell was observed, 

 which bad been transmitted very quickly through the tuhe by the act of corking up 

 the other end with the stopper carrying the odoriferous material. This first wli iff, 

 liowever, lasted only a very short time, and then a long period elapsed before 

 any further smell could be detected at the free end of the tube, whether that end 

 was left open or closed between times. Finally, however, after, for example, 

 about eighteen minutes in the case of a three-feet horizontal tube, having a large 

 cotton-wool sponge saturated with oil of limes attached to one cork, the smell 

 tecame definite and recognisable. 



It would, therefore, appear that the passage of smell is generally far more due 

 to the actual motion of the air containing it than to the diffusion of the odoriferous 

 .substance through the air. And, as a striking illustration of this, the following is 

 interesting: — After the stopper had been in contact with the odoriferous substance 

 for some time, it, of course, acquired a smell itself, which gradually spread in the 

 rnom in which the experiment was made. And although this smell was due simply 

 to the exposed part of the stopper, while ilie air inside the tube was at one end in 

 contact with a mass of the odoriferous substance itself, the only place where the 

 .smell could not be detected during the course of the experiment was the space 

 inside the open end of the glass tube. And, what seemed very surprising, it was 

 found necessary, in several cases, to blow air through the room to clear out the 

 smell which emanated from the outside of the stopper before the smell coming 

 along the tube from the mass of odoriferous substance which was ittside it at 

 the other end could be detected. A further proof of the important part played by 



of unsaturated hydrocarbons belonging to the define and other series. In view of 

 the fact that marsh gas at one end of the scale and paraffin wax at the other are 

 both practically odourless, it is doubtful whether the liquid paraffins have much 

 smell 7vhen pure, and it would, therefore, appear probable that the hydrocarbons 

 which give the peculiar odour to the hydrogen escaping from iron raay be the 

 unsaturated compounds referred to above. 



