240 THE CHEMISTRY OF CREATION. 



weather it decomposes, and produces that pecu- 

 liarly disagreeable organic smell which no words 

 can describe, but which is only too familial* to 

 our senses in the abodes of misery and poverty. 

 In contrasting this condensed animal exhalation 

 with dew collected in the open air, the most 

 remarkable difference is found to exist. The 

 dew remained beautifully clear and limpid, 

 even when boiled down ; the odour was not re- 

 markable ; and when the small portion of solid 

 matter which remained dissolved in it was ex- 

 posed to heat, the smell was that of vegetable 

 matter, with very little trace of any nitrogenised 

 substance. It was also rather agreeable than 

 otherwise. 



From these researches it is quite manifest that 

 organic matters are always present in the air of 

 towns. Occasionally, in close unhealthy neigh- 

 bourhoods, it may even be perceived by the 

 sense of smell, and that it is not more evident 

 to us when entering a large city from the open 

 country, and fresh air, is due chiefly to the cir- 

 cumstance of our becoming by degrees accus- 

 tomed to it during the time occupied in our 

 journey. Could a Highlander be suddenly 

 transported from his heather-covered hills, and 

 set in the midst of a densely-populated alley in 

 London, he would instantly be sensible of the 

 existence of a great degree of impurity in his 



