IRRIGATION. 209 



nected with the old saying, that "the snow is the 

 poor man's manure," it may be worth while to ex- 

 amine the foundation of this proverb. Like all oth- 

 ers of this class, it will be found to rest on observa- 

 tion, and is supported by experiment. In 1751, 

 Margraf, in the neighborhood of Berlin, after it had 

 snowed several hours, collected in glass vessels, as 

 much falling snow, as afforded 3600 ounces of water. 

 This carefully evaporated, afforded 60 grains of cal- 

 careous matter, with some grains of muriatic acid, 

 and traces of nitrous vapour. An equal quantity of 

 rain water, afforded 100 grains calcareous matter, 

 with some muriatic acid ; and in both cases the mat- 

 ter was discoloured by an oily substance. A similar 

 result was obtained long ago in Ireland, by Dr. Rut- 

 ty, who found in a gallon of snow water, 4 grains, 

 and in one gallon of rain water, 6 grains of calcareous 

 matter. This is about the proportion found by Mar- 

 graf, and would give for each inch of snow water 

 about 10 lbs. of salts per acre. From the existence 

 of free acids in this case, it is evident that no carbon- 

 ate of ammonia could have there existed. There 

 are some experiments performed by our countryman, 

 Dr. Williams, formerly Hollis Professor of Math- 

 ematics and Natural Philosophy in Harvard College, 



and detailed in the first volume of his history of Ver- 



18* 



