OF PLANTS BY MANURING. 57 



chemist might add, this power in the case before us 

 is called ammonia. 



Another experiment is the following. If the tu- 

 ber of a hyacinth is wrapped round with a few thin 

 horn-shavings, and put into the earth by the side of 

 another without this envelopment, a plant will grow 

 up from the former perhaps double the size of that 

 produced by the latter. In horn-shavings there are, 

 except nitrogen, no fertilizing constituents of much 

 importance ; it must therefore be this substance to 

 which the extraordinary increase in the growth of 

 the hyacinth is properly due. In this experiment 

 the forcing power is developed at a much later pe- 

 riod than in that with the leaves of the rape or beet 

 plant; because the nitrogen of the horn must be 

 changed into ammonia, by putrefaction in the earth, 

 before it can operate. The same effect is produced 

 when the hyacinth, or any other plant which is culti- 

 vated in pots, is sprinkled with glue-water. In glue, 

 likewise, there is no other powerfully fertilizing in- 

 gredient than nitrogen ; but this must be first set 

 free by putrefaction, and for this reason even here 

 the effect does not immediately happen. When, on 

 the other hand, the glue-water is suffered first to be- 

 come putrid, it operates more briskly ; a fact which 

 now needs no further explanation. 



Further information upon the value of this impor- 

 tant agent in manure, and the means of retaining it, 

 will be communicated in our observations upon in- 

 dividual manures. To prevent misapprehension, we 



