Natural History of Nova Scotia. 659 



by the leaves of plants when exposed to light, and, being 

 decomposed by their action, the part which rendered the 

 air unwholesome to animals is retained, and serves to nourish 

 the plant ; while, at the same time, they emit the remainder 

 in a state of pure perishable [respirable] air. 



As a large proportion of the richest manure is quickly 

 changed by putrefaction into noxious vapours, it is for the 

 health of man that nothing which will serve to fertilise the 

 soil should be neglected, and that cultivation should be pushed 

 to the uttermost. It is also both for his health and his in- 

 terest to preserve the forest, or to permit nature to reproduce 

 it where it has been destroyed by fires, in those situations 

 which are not required for cultivation or pasturage; since 

 it is certain that uncultivated land, exposed to the sun con- 

 tinually, for a long time, becomes more barren, and that land 

 overgrown with wood is for a long time slowly becoming 

 more fertile. 



Nature has strongly pointed out to man that he ought not 

 to reside near to putrefying animal or vegetable substances. 

 They are disgusting to his senses; most useful to him as 

 manures. When he neglects his duty, other animals are 

 provided to assist him. Large towns are usually overrun 

 with dogs, most of which are kept for no other reason than 

 the attachment felt by their owners for those humble, loving, 

 and ever-faithful dependents. Were manure as carefully 

 collected here as it is said to be in China and Japan, they 

 might prove a nuisance ; but here they are certainly useful. 

 They live principally upon the offal in the streets and yards, 

 and are well entitled to their living. With all our poverty, 

 we have not heard of any person dying of hunger in Halifax; 

 but there is good reason to believe that the removal of the 

 dogs would cause numbers to die of pestilential diseases. 

 The flies in our yards and houses have a similar employment. 

 The effluvia of those substances, which taint the air, point out 

 [to them those substances as] the proper nidus for their 

 young, who [which], by speedily devouring them, in a great 

 measure prevent their decomposition. These, in a few weeks, 

 become flies, and enter our houses in swarms at the close of 

 the hot season, when the air is more than at any other time 

 charged with deleterious vapours. The motion of their wings 

 performs, in our apartments, the same office that the winds 

 do abroad, in preventing the separation of the different kinds 

 of air : for it is well known that the noxious aerial fluids, which 

 are most abundant, are either heavier, or much lighter, than 

 common air ; and were thev not kept in motion, they would 



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