202 FERGUSON'S 



All common air is impregnated with a certain kinu 

 of vivifying spirit or quality, which is necessary to con- 



tinue tlie lives of animals : and tm ' s > in a gallon of air, 

 in air. is sufficient for one man during- the space of a minute, 

 and not much longer.** 



This spirit in air is destroyed by passing through the 

 lungs of animals : and hence it is, that an animal dies 

 soon after being put under a vessel which admits no 

 fresh air to come to it. This spirit is also in the air 

 which is in water : for fish die when they are excluded 

 from fresh air, as in a pond that is closely frozen over. 

 And the little eggs of insects, stopped up in a glass, do 

 not produce their young, though assisted by a kindly 

 warmth. The seeds also of plants mixed with good 

 earth, and inclosed in a glass, will not grow. 



injnry to the health of the people. They feel, indeed, very weak and re- 

 laxed after it ; but a few hours of the Tramontane or north wind, which 

 generally succeeds it, soon braces them up again, and restores them to 

 their former state. However, in Naples, and some other parts of Italy, 

 where its violence is not to be compared with that of Palermo, it is often 

 attended with putrid disorders, and seldom fails to produce almost a 

 general dejection of spirits. But there the sirocco lasts for many days, 

 and even for weeks ; so that, as its effects are different, it probably pro- 

 ceeds from a different cause. Some have supposed that this is the same 

 wind with that which is so dreadful in the sandy desarts of Africa, where 

 it sometimes proves mortal in the space of half an hour; but that in its 

 passage over the sea, it is cooled and deprived of its tremendous influence, 

 before it reaches Sicily. If this were true, we might expect to find it 

 most violent on that side of the island that lies nearest to Africa, which is 

 not the case ; though it is possible, that its heat may be again increased 

 by its passage across the island to Palermo, near the most northern part : 

 and besides, this city is almost surrounded by very high mountains, the 

 ravines and valleys betwixt which are entirely parched up and burning 

 hot at this summer season of the year. These likewise contain springs of 

 warm water, the steams of which may increase the heat, and at the sam 

 time soften the air, so as to disarm it of its noxious qualities. 



Note 55. Ihe vivifying spirit liere alluded to, is essential to com- 

 bustion, no less than to animal life ; and this important constituent of 

 our atmosphere is now better known by the term oxygen. It is a 

 gaseous fluid, and (onus about one fourth of the air that surrounds 

 ui. 



