96 THE SOIL. 



particles that the plant derives the phosphoric acid, 

 potash, sihcic acid, &c., as well as the ammonia. These 

 substances are introduced into the plant by means of the 

 thin layer of water, the molecules of which are in motion 

 only in so far as the roots exercise an attractive power 

 upon them. 



From the composition of spring- water, and the water 

 of brooks and rivers, every single drop of wliich has been 

 in contact with rocks, or with the soil of forests and fields, 

 we see what exceedingly minute quantities of phosphoric 

 acid, ammonia, and potash are taken up by water from 

 the earth. In the analysis of water taken from six 

 dilTerent springs, Graham, Miller, and Hofmann found 

 no appreciable traces of ammonia and phosphoric acid. 

 In the water of Whitley, there was, in 37,000 gallons 

 (370,000 pounds English), 1 pound of potash, or 1 kilo- 

 gramme in 135 cubic metres : just the same in 38,000 

 gallons from the Critchmere spring ; in 32,000 gallons 

 from Velwool ; in 145,000 gallons from Hindhead ; in 

 55,000 gallons from the Hasford IMillbrook ; and in 

 17,700 gallons from the spring near Cosford House. The 

 water of the Brunthal spring, near Munich, which is used 

 for drinking in a large portion of the city, contains no 

 ammonia, no phosphoric acid, and in 87,000 pounds, 

 1 pound of potash. 



From these and other analyses of spring, well, and 

 drainage water, we are not warranted in concluding that 

 potash, ammonia, and phosphoric acid are deficient in the 

 water of aU springs, brooks, and rivers ; on the contrary, 

 it is quite certain that the Avater in many marshes contains 

 both potash and phosphoric acid in notable quantities.* 



* Thus a litre (1'7G pints) of Avater taken from an artificial jiond in 

 tlie Botanic Garden at Munich, left a residue of 0*4:25 gramme 

 (6"5 grains), Avhicli contained, in 100 parts — 



