134 AGRICULTURE. 



No other farm animal is so much affected by its surroundings 

 as the sheep. As a consequence we find so many different 

 varieties, and for this reason we must be careful to choose the 

 variety that is most likely to do well in the conditions of the 

 farm on which they are desired to be grown such as situation, 

 climate, etc. Why is wool warm ? Because it is fine and 

 open and holds so much air in its fibres, and this air prevents 

 the heat of the body from going off; as we say it is a poor 

 conductor of heat. It is not because it keeps out cold, but 

 because it keeps in the heat of the body. If you wrap a 

 piece of ice in a loose thick woollen cloth it will prevent the 

 ice from melting rapidly. Why ? Because the heat outside 

 does not pass through or get in. Double windows in a house 

 are a protection, not because of the glass in the panes, but 

 because of the air between the two windows. So the hollow 

 space in the wall of a silo keeps in the heat of the ensilage, 

 and thus prevents it from freezing. A covering of loose snow 

 protects the wheat for the same reason. Now that we under- 

 stand that wool keeps the sheep warm while it is on the sheep's 

 back, we ask why wool can be made into yarn and cloth. If 

 you look at a fibre of wool under a magnifying glass you will 

 see that it is made up of sections, that there are little joints or 

 scales on the wool and when several fibres are twisted together 

 these little scales catch into one another and the fibres thus 

 hold together tightly the wool, as we say, "felts" well. There 

 comes from the skin of the sheep a soapy substance called the 

 "yolk," which covers the inner wool and helps to shed the 

 rain. It prevents the wool from felting on the sheep's body. 

 When the fleece is washed this is washed out and the fleece 

 becomes much lighter. Sheep are by nature fitted to stand 

 cold, but not wet weather they should always have dry quarters. 

 BREEDS OF SHEEP. Sheep of various breeds are found in 

 Britain, from the marsh lands of Kent to the mountains of 

 Wales and Scotland. They have adapted themselves in time 



