1g8 Bibliography. 
them. Would he know what varieties of domestic animals may be 
most advantageously raised for any particular purpose, or how certain 
qualities may be obtained by cross-breeding ; zoological knowledge 
will afford him important assistance. If it be desirable to ascertain 
whether a certain crop, or kind of fruit, may be expected to succeed in 
a given district; meteorology provides the data for resolving the en- 
quiry, by giving the mean temperature of the year, recording the 
greatest heat of summer and cold of winter for a series of years, the 
liability to sudden and great changes of temperature at particular sea- 
sons, the average quantity of rain which falls during each year, or 
month. These data, compared with: the atmospheric condition of 
country where the crop in question is successfully cultivated, afford the 
requisite information. The nature of the soil no Jess demands the 
farmer’s attention; the character of the subsoil, and the results that 
may be expected from bringing it to the surface ; the cause of the di- 
versities which different portions even of the same field exhibit, where 
the land is to ordinary observation similar ; these and similar points 
geology offers to explain. “gh aaen 
Moreover, if a soil be netitrally eS or be yesiieied so iy a long- 
continued system of wretched tillage, like that which has impoverished 
extensive portions of our Southern States, it is very important to know 
whether it may be improved or reclaimed so as to repay the outlay, 
and how this may best be effected. Barrenness may be owing to the 
presence of some injurious substance, or it may arise from the absence 
of an element that is essential to the production of a given crop. How 
is the cultivator to distinguish between these two cases, and apply to 
each the proper remedy? When a field is exhausted by over-croppings 
how are we to ascertain what is exhausted, and consequently what must 
be restored to the soil before it can recover its former fertility ? “To 
these and to a thousand such questions, ‘“ chemistry alone can and w 
give a satisfactory answer.” Jt is true that many useful results have 
been 1ed by mere accident, and pursued apart from all considera- 
tions of the why and wherefore ; but it is no less true that we know not 
half the value of any such discovery, until we understand the _prinel- 
ples upon which it rests, and can apply them intelligently to 
: Gypsum, for instance, is found wonderfully to fertilize certain 
ned while upon others it produces no good effect whatever. It is ob- 
Yiou that the farmer cannot derive the fullest advantages from this 
: y nor be t a with all its useful appli¢ations, until he under- 
Eire 
