106 PRINCIPLES OF GARDENING. [CH. II. 



muriate of ammonia (sal-ammoniac), carbonate of am- , 

 monia (volatile salt), and acetate of ammonia. Night I 

 soil, one of the most beneficial of manures, surpasses ' 

 all others in the abundance of its ammoniacal con- 

 stituents in the proportion of 3 to 1 . It may be ob- 

 served, that the nearer any animal approaches to 

 man in the nature of its food, the more fertilizing is 

 the manure it affords. I have no doubt that a lan- 

 guishing plant one, for example, that has been kept 

 very long with its roots out of the earth, as an orange 

 tree recently imported from Italy, might be most 

 rapidly recovered, if its stem and branches were steeped 

 in a tepid, weak solution of carbonate of ammonia, 

 and, when planted, an uncorked phial of the solution 

 were suspended to one of the branches, to impreg- 

 nate the atmosphere slightly \\ith its stimulating 

 fumes. 



Manures are also of benefit to plants, by affording 

 some of the gases of the atmosphere to their roots, 

 in a concentrated form. A soil, when first turned up 

 by the spade or plough, has generally a red tint, of 

 various intensity, which, by a few hours' exposure to 

 the air, subsides into a grey or black hue. The 

 first colour appears to arise from the oxide of iron, 

 which all soils contain, being in the state of the red or 

 protoxide ; by absorbing more oxygen during the ex- 

 posure, it is converted into the black or peroxide. 

 Hence one of the benefits of frequently stirring soils : 



