198 
Peruvian Guano. 
Water as a Solvent for Guano. 
It lias been frequently noticed that Peruvian guano is not so 
efficacious in a dry season or localities as in a wet season or in dis- 
tricts where the rain-fall is high. This perhaps is one, but not the 
only reason why Peruvian guano is so highly and justly appre- 
ciated in the West of Scotland, and generally in the western 
counties, and why in several of the eastern counties it has been 
superseded in a great measure by superphosphate of lime. 
Again, it has been observed that Peruvian guano is never more 
beneficially applied to the land than when a sufficient length of 
time is allowed for the rain to wash it into the land. These and 
similar observations tend to show that guano, like most highly- 
concentrated manure, produces the most beneficial effect upon 
vegetation when it has become thoroughly acted upon by water 
and its constituent elements have been uniformly diffused through 
the soil. That guano should be applied to the land at a time 
when heavy showers of rain or a succession of wet days may con- 
fidently be expected, is a rule with all good farmers ; and it 
remains for the agricultural chemist to point out the reason why 
this should be done, and also to explain why, on the same soil 
and upon the same crop, guano at certain times acts much more 
beneficially than at others. The difference in the practical efficacy 
of Peruvian guano is intimately connected with the action of water 
on its constituents. A comparatively small quantity of water 
corresponding to a mere passing shower of rain falling on a field 
recently manured with guano appears to have a different effect 
from that of a large downfall on its constituents ; as this subject 
has a direct practical bearing upon agricultural practice, I have 
carefully studied the action of water upon guano, and now proceed 
with a description of my experiments and a statement of my 
results. 
' Experiments showing the effects of a definite and large quantity 
of Water on Peruvian Guano. 
The same three samples of guano, the composition of which is 
given in the beginning of this paper, were employed in the fol- 
lowing experiments : — 
100 grains of each sample were boiled up for a few minutes 
with half a decigallon of distilled water, another half decigallon 
of cold distilled water was added, and the mixed and muddy 
liquid allowed to settle for 24 hours in a stoppered glass-bottle. 
The clear liquid was then filtered off, and the insoluble matter 
collected, on a weighed filter. The insoluble matter was dried 
in a waterbath, weighed, and then burned. In' the burnt residue 
the percentages of sand, insoluble phosphates, oxalate of lime, 
