236 IRRIGATION. 



It is a question whether this is not the source of the am  

 monia discovered in rain water. It is taken for granted, 

 that the ammonia in rain water exists as a volatile carbon- 

 ate, because it was found to pass over in distillation. So 

 does a volatile product, which always discolors the crystals 

 of sal-ammoniac, procured by adding muriatic acid to the 

 distilled water. This discoloring matter was noticed a cen- 

 tury ago by Margraff. Later chemists have also detected 

 ammoniacal salts in rain water, but no volatile carbonate of 

 that base. It is well known that muriate of soda arises in 

 evaporation, so does chromate of potash, and several other 

 salts. If, in distilling rain water, the ammonia did not pass 

 over in the volatile organic discoloring product, it may have 

 gone over as muriate of ammonia. It is not questioned that 

 ammoniacal salts exist in rain and snow water. The fact that 

 it there exists as carbonate seems to be assumed, and is 

 incompatible with the salts which have been heretofore ob- 

 tained, from rain, snow, and hail. The subject has of late 

 excited much attention, and as the existence of salts in snow 

 is intimately connected with the old "Saying that " Snow is 

 the poor man's manure," it may be worth while to examine 

 the foundation of this proverb. Like all others of this class 

 it will be found to rest on observation, and is supported by 

 experiment. In 1751, Margraff, 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 

 calcareous matter, with some grains of muriatic acid, and 

 traces of nitrous vapor. An equal quantity of rain water 

 afforded 100 grains calcareous matter, with some muriatic 

 acid ; and in both cases the matter was discolored by an oily 

 substance. A similar result was obtained long ago in Ire- 

 land, by Dr. Rutty, who found in a gallon of snow water, 



