Injiaeace of Climate, S,-c., on Sheep. 
105 
form Ave necessarily modify the internal organisation ; the lungs 
and tlie liver are rendered smaller and less active, and tlie fatty 
matter of the blood, being less perfectly burnt off in the body, is 
stored away as fat ; but just in the same degree do we limit the 
power of that animal to maintain its natural heat, a certain 
amount of which is absolutely necessary for the healthy action 
of the animal system. If, therefore, an animal be placed in a 
climate so severe that this warmth of the body cannot be main- 
tained, either from the diminished activity of the lungs or the 
inadequacy of the food supplied, the body becomes unhealthy 
for lack of heat. Our mountain sheep arc so constituted that 
they can, with a proper supply of food, be kept upon these 
elevated pastures with great advantage ; and were they discarded, 
we have no other breed capable of enduring the same rigour of 
climate when living upon the same herbage. If any important 
improvement should be introduced into the ordinary system of 
mountain farming, the mountain sheep must still be the basis of 
any flock which is likely to be remunerative to the occupiers 
of those elevated grazing lands, and for these reasons our moun- 
tain sheep must be preserved in all their native strength and 
purity. 
On all but strictly mountain farms in a state of nature, cross- 
breeding will most effectually promote improvement. Pure bred 
mountain ewes are often driven into more favoured districts, 
where the climate is more equable, the crops more abundant, 
and the labour of securing the supply of food very much reduced. 
Under such circumstances we may, by cross-breeding, readily 
imj)art to their offspring a greater rapidity of growth, and at the 
same time an aptitude for fattening and for the production of a 
good fleece. This is often done in the mountain districts when 
the ewes have been drafted for sale. They are crossed with a 
superior ram, and thereby they become more marketable. This 
will be most satisfactorily accomplished, not by the rams of any 
one breed, but by a selection of rams from the most improved 
sheep upon the eastern boundary of each portion of our mountain 
district. Thus the black-faced mountain sheep of Westmorland 
Avill be most improved by superior Cheviot rams, the Welsh 
mountain sheep by good Shropshire Downs and Ryeland rams, 
and the sheep of Esmoor and Dartmoor by the use of the 
Notts and Leicester. This is the natural and practical system of 
cross-breeding from mountain ewes, and one very generally 
adopted ; not that it is the only system of cross-breeding by which 
the desired result may be obtained, but the evidence of ex- 
perience is clearly in favour of this natural arrangement. 
The reason, why these rough ewes produce lambs which 
equal in quality the produce of more valuable ewes, demands 
