On Bats' Guano. 
61 
products of the action of water upon accumulations of the fa?cal 
matter of sea-birds, and of the remains of marine animals. The 
invariable presence of nitrogenous organic matters, yielding 
from i to I per cent, of nitrogen on an average, and the fine 
powdery condition of all true phosphatic guanos, plainly indicate 
their origin and mode of production. 
Nitrogenous and phosphatic guanos clearly have a common 
origin ; and the latter being, comparatively speaking, quite recent 
products of decomposition, may be appropriately described as 
true guanos. But it appears to me objectionable to give the 
name of " Rock guano " to Sombrero and Cura(}ao Rock, or to 
Alta Vela, Redonda, and similar phosphatic minerals, essen- 
tially differing in physical characters from Mejillones, Maiden 
Island, Starbruck Island, or Lacepede and other phosphatic 
guanos, and possessing still less in common with Peruvian, 
Saldanha Bay, Ichaboe, and other kinds of birds' dung which are 
rich both in ammoniacal and phosphatic constituents. 
Guanos from which nearly the whole of the nitrogenous and 
saline constituents have been removed, by rain and other atmo- 
spheric agencies, contain the phosphatic elements in a finely 
divided condition ; and although their efficacy as manures is, 
no doubt, much enhanced by treatment with acids, they may in 
virtue of their fine condition be applied to the land with more 
or less advantage in their natural state. On the other hand, 
Alta Vela, Redonda, and other phosphatic minerals, the origin 
of which is shrouded in mystery, and which are found in nature 
in the shape of rocks or stones, frequently contain little or no 
trace of organic matter, while the phosphatic constituents are in 
a completely mineralised state. Materials of that kind, in my 
judgment, cannot be applied to the land with advantage, unless 
they have been subjected to chemical treatment, and thereby 
converted into efficient manures. 
If applied to ground phosphatic minerals, the name of guano 
appears to me misleading ; for it conveys the impression to the 
mind of practical men that such minerals, merely reduced to a 
fine powder, may be employed for manuring purposes, in the same 
manner as true guanos, without previous treatment with acids. 
I allude to this matter, because instances have been brought 
under my notice, by farmers who applied ground phosphatic 
minerals, which had been sold to them as guano, as a top- 
dressing for corn-crops, under the wrong impression that they 
would produce effects similar to those which nitrogenous guanos 
are well known to produce upon corn-crops. It is scarcely neces- 
sary to observe that it is a sheer waste of time and money to 
top-dress wheat or barley with ground minerals containing no 
ammonia whatever. 
