210 IRRIGATION. 



mont, where the experiments were performed. In 

 1791, 6 gallons of fresh falling snow water, afforded 

 by evaporation, 11 grains calcareous matter, 2 grains 

 of saline matter, 5 grains of a dark brown oily mat- 

 ter. In January, 1792, 6 gallons of snow water, 

 from snow lying three inches deep on the grass, on 

 an area of 16 square feet, where it had lain 59 days, 

 covered with a depth of 27 inches of snow, afforded 

 the same salts as above, and 105 grains of this oily 

 matter. This is the most remarkable fact, and may 

 afford some weight to the suggestion before made, 

 that organic matter exists gaseous in the air. It 

 must have been drawn up by capillary attraction, or 

 evolved from the surface of the earth. It is there 

 condensed by the snow, and returned to the earth, 

 impregnated with its salts of lime and ammonia. 

 The snow is " the poor man's manure." It not only 

 adds salts and geine, but prevents the escape of the 

 last. But is it possible that it should escape in the 

 cold ? Doubtless it does when the ground is not 

 frozen. The snow by its warm mantle actually pre- 

 vents the earth growing colder, and as has been inge- 

 niously suggested, keeps up an imperfect vegetation. 

 The snow thaws frozen ground. In 1791, Professor 

 Williams found that the ground which had been fro- 

 zen 6 inches in depth, before the snow fell, not only 



