208 IRRIGATION. 



drop or two of milk ; by standing, the water grows 

 clear, and the flocky matter which settles, burns with 

 the smell of animal matter, and evolves ammonia. 



It is a question whether, even at the Giessen la- 

 boratory this was not the source of the ammonia, 

 there discovered in rain water. It is taken for grant- 

 ed, that the ammonia in rain water existed as a vola- 

 tile carbonate, because it was found to pass over in 

 distillation. So did a volatile product, which always 

 discoloured the crystals of sal ammoniac, procured by 

 adding muriatic acid to the distilled water. This dis- 

 colouring matter, was noticed a century ago, by Mar- 

 graf. Later chemists have also detected ammonia- 

 Gal 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 organ- 

 ic discolouring product, it may have gone over as 

 muriate of ammonia. It is not questioned that am- 

 moniacal salts exist in rain and snow water. The 

 fact that it there exists as carbonate, seems to be as- 

 sumed, and is incompatible with the salts which have 

 been heretofore obtained, from rain, snow and hail. 

 This subject has of late excited much attention, and 

 as the existence of salts in snow, is intimately con- 



