DOCTRINE OF SPONTANEANS DISPROVED. 
large, and have much small crooked timber divided among them. A 
tree standing in a plantation follows the same law of nature, hut by 
judicious thinning and pruning will form a stem of considerable 
length, while in a good growing state, care, therefore must be taken 
at all times to have a good head, if you mean to have stem, and when 
you have length of stem the head cannot be too large. Thus the 
fewer trees you have on an acre of land the better, if the tops cover 
all the ground ; for the timber will certainly be of larger dimensions, 
and consequently the more valuable. In plantations grown to limber 
size, a tree that will square a foot is of considerable more value than 
four that square six inches each, as every carpenter can tell. And 
now we are mentioning timber, let us say a word or two about the 
growing of it. Some gi-eat authors tell us that timber cannot be 
good if raised any way by cultivation and manuring, and that every 
method employed must be as near nature as jiossible to make it 
valuable ; but if the experiments made by practical men may be de¬ 
pended upon, timber that has grown the fastest is the strongest and 
best. It follows, therefore, that land intended for planting, (if not 
very rich) may be trenched and manured according to garden prac¬ 
tice for a common crop, such as potatoes and turnips. 
I have thus put together the methods I have followed in pruning 
plantations for many years. They will not be of much use to you 
at present, as your plantations are under excellent management; but 
they are yet young, and as my experience is of earlier date than 
3 'ours, perhaps as they get older, some of 1113 ^ hints may be of service 
to 3 ou. 
I am. Dear Sir, truly yours, 
John Sandys 
Wells, December Si'd. 1829. 
NATURAL HISTORY. 
ARTICLE XII.—DOCTRINE OF SPONTANEANS DISPROVED. 
BV AN IMPORTANT DISCOVERT OF M. EHRENBERG. 
It is well known that b 3 " far the greater number of our living natu¬ 
ralists and jdiysiologists, believe in the doctrine of spontaneant gene¬ 
ration, chiefl 3 ^ because they could not discover that microscopic ani¬ 
malcules, or monads as they called them, are produced from parents, 
l^eing, therefore, unable to discover this, thev forthwith concluded 
