34 PRINCIPLES OF GARDENING. [CH. I. 



round the eaves of every structure in the garden, and 

 coramimicate with them. Every 100 cubic inches of 

 rain water contains more than 4 cubic inches of air, of 

 wliich more than half are carbonic acid gas, and the 

 remainder nitrogen and oxygen, in the proportion of 

 62 of the fonner to 38 of the last named. Liebig, 

 from actual experiment on a large scale, states that 

 both rain and snow contain ammonia; and its 

 importance appears from the fact that, if there 

 be only one-fourth of a gi'ain in each pint of water, 

 the annual deposition from the atmosphere would be 

 more than sufficient, on half an acre of ground, to 

 give all the nitrogen contained in the vegetable albu- 

 men of 150 cwt. of beet root. Ram water also 

 contains a peculiar substance, analogous to the ex- 

 tractive matter and gluten of plants, though dif- 

 fering from them chemically. To this substance Dr. 

 Daubeny has given the name of Pyrrhine. Traces of 

 salts and oxides have also been found in rain water ; 

 but compared ^vith all other naturally produced, it is 

 so pure, and so abounds with the gases beneficid to 

 plants, that none other can equal it for their service. 

 That obtained from ponds or sprmgs invariably con- 

 tains matters offensive or deleterious to plants. That 

 known as hard water, containing in excess salts of 

 lime or magnesia, is invariably prejudicial, and pond 

 water is scarcely less so. If it be stagnant and loaded ' 

 with vegetable extract, it is even worse than hard 



