372 
AGRtCULTlTRE. 
to be hoped, may be formed by a trigonometrical 
survey of the whole Union. This would give em- 
ployment to an army of civil engineers who are 
now reposing in idleness, and prove a vast field of 
industrious employment, the results of which would 
be alike useful and honourable to the nation. 
AGRICULTURE. 
The intimate connexion of geology with agricul- 
ture must strike the most superficial observer. On 
this subject, the following remarks of Mr. Bakeweli 
are well worthy of attention : *' By a wise provision 
of the Author of Nature, it is ordained that those 
rocks which decompose rapidly are those which 
form the most fertile soils ; for the quality of soils 
depends on the nature of the rocks from which they 
were formed. Granite and silicious rocks form 
barren and sandy soils; argillaceous rocks form 
stiff clay ; and calcareous rocks, when mixed with 
clays, form marl ; but, when not covered by other 
strata, they support a short but nutritious vegeta- 
tion. For the formation of productive soils, an in- 
termixture of the three earths, clay, sand, and Ume, 
is absolutely necessary. The oxide of iron also 
appears to be a requisite ingredient. The propor- 
tion necessary for the formation of a good soil de- 
pends much on the nature of the climate, but more 
on the quality of the subsoil, and its power of re- 
taining or absorbing moisture. This alone may 
make a soil barren, which, upon a different subsoil, 
would be exceedingly productive. When this is the 
case, either drainage or irrigation offers the only 
means of permanent improvement." Again he re- 
marks, that, " in proportion as soils possess a due 
degree of tenacity, and power of retaining or ab- 
sorbing heat and moisture, the necessity for a sup- 
ply of manure is diminished, and in some instan- 
ces the earths are so fortunately combined as to 
render all supply of artificial manure unnecessary 
