ELEMENTS OF AGRICULTURE. 
47 
bodies that it is derived from. That from fecal matters 
fpoudrette) is more active than that derived from the ex¬ 
crements of animals. It is pretended that humus accruing 
from horses and birds produces a better effect on the soil 
than that from cattle. It is admitted that the excrements 
of pigeons and poultry are much more active, in similar 
quantities, than manures derived from other animals. We 
should not, however, as we shall see hereafter, attach too 
much importance to these distinctions in the value of the 
manures in more general use. 
60. Matters derived from animals, entering easily into 
putrefaction, furnish a humus of better quality than that 
proceeding from vegetable matter ; for these are often de¬ 
composed with great difficulty. 
61. Humus is sometimes acid, particularly in low and 
wet places, such as turf is formed in. When it has this 
property, it is injurious to vegetation. In this case, to 
render it fit food for plants, calcareous substances, such as 
lime, are put in the soil; and they are in this instance a 
very efficient remedy. Moreover, in lands that contain 
carbonate of lime, sour humus is never found. Animal 
black may be substituted for carbonate of lime; it is a 
substance derived from the calcination of bones. 
62. Paring and burning , also, destroy the acidity of 
the soil. It consists in paring off the crust of the earth, 
some two or three inches deep, burning it in small hillocks, 
and in scattering the ashes. This operation has also tb® 
advantage of destroying noxious weeds and insects. 
QUESTIONS. 
1. What is humus ? 
2 . Is it always composed of the same elements ? 
3. By what other name is it called ? 
4. Where are the bodies decomposed that form humus 
5. Where is turf found ? 
6. By .what are turf lands recognised? 
7 . What use is made of turf ? 
