METEOROLOGY. RAIN. 493 



8.174 inches in the night : of 5.934 inches which fell in December, 

 0.786 inches fell in the day, 5.148 inches in the night. 



Two series of observations taken in the same country al two sta- 

 tions not far from one another, but situated at very different eleva- 

 tions, seem to confirm, in reference to the equatorial regions, the 

 conclusions of European meteorologists as to the fact that the an- 

 nual quantity of rain which falls diminishes as the height above the 

 level of the sea increases. They also show that in latitudes which 

 do not differ materially, more rain falls where the mean temperature 

 is 68° F. than where it is 58° F. 



Marmato lies in N. lat. 5° 27", and 75" 11" (?) W. long., at a 

 height of 4676 feet above the level of the sea ; Santa Fe in N. lat. 

 4° 36'', W. long. 75° 6", at a height of 8692 feet above the level of 

 the sea. And while the quantity of rain at the former place amount- 

 ed, according to my own observations for 1833, to 60 inches, ac- 

 cording to Caldas, in 1807, at the latter there fell but 39.4 inches. 



In temperate climates the quantity of rain that falls varies with 

 the seasons. Near the equator, where the temperature remains 

 constant throughout the year, the rainy season conmiences precisely 

 at the period when the sun approaches the zenith ; and whenever the 

 latitude of a place in the torrid zone where it rains is of the same 

 denomination and equal to the declination of the sun, storms occur. 

 In such circumstances the sky in the morning is of remarkable pu- 

 rity, the air is calm, the heat of the sun insupportable. Towards 

 noon clouds begin to show themselves upon the horizon, the hygrom- 

 eter does not advance towards dryness as it usually does, it remains 

 stationary, or even falls towards extreme humidity. It is always 

 after the sun has passed the meridian that the thunder is heard, 

 which being preceded by a light wind is soon followed by a deluge 

 of rain. In my opinion the permanence or incessant renovation of 

 storms in the bosom of the atmospliere is a capital fact, and is con- 

 nected with one of the most important questions in the physics of 

 our globe, that of the fixation of the azote of the air by organized 

 beings. 



The most recent inquiries show dry atmospherical air to consist 

 in volume of: 



Oxygen 20.8 



Azote 79.2 



The air contains in addition from 2 to 5 10,000ths of carbonic acid 

 gas, and quantities perhaps still smaller of carbureted combustible 

 gas. The experiments of M. Theodore de Saussure, as well as 

 those of Professor Liebig, have further demonstrated in it traces of 

 ammoniacal vapor. 



I have already shown that animals do not directly assimilate the 

 azote of the atmosphere. Azote is nevertheless an element essen- 

 tial to the constitution of every living being, and is met with indif- 

 ferently in either kingdom of nature. If we inquire into the source 

 of this principle in connection with the herbivorous tribes of animals, 

 we find it as an element in the food which sustains them. If we 

 next inquire into the immediate origin of the azote which enters 



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