What lime does to clay 



21 



with rain water and about ^ its weight of lime. The 

 limed clay breaks easily and works quite differently from 

 the pure clay. 



Summary. This, then, is what we have learnt about 

 clay. Clay is made up of very, very, tiny pieces, so small 

 that they float in water. They stick together when they 

 are wetted and then pressed, and they remain together ; 

 a piece of clay moulded into any pattern will keep its 

 shape even after it is dried and baked. Clay is therefore 

 made into bricks, earthenware, pottery, etc., whilst white 

 clay, which is found in some places, is made into china. 

 Wet clay shrinks and cracks as it dries ; these cracks 

 can easily be seen in the fields during dry weather. This 

 shrinkage interferes with the foundations of houses and 

 other buildings, causing them to settle. Dry clay is 

 different from wet clay, it is hard, not sticky and not 

 slippery, but it at once becomes like ordinary clay when 

 water is added. After baking, however, clay permanently 

 alters and cannot again be changed back to what it was 

 before. Clay will not let water pass through ; a clay 

 field is therefore nearly always wet in winter and spring. 

 Nor can air pass through until the clay dries or cracks. 



Lime has a remarkable action on clay. It makes the 

 little, tiny pieces stick together to form feathery flocks 

 which sink in water ; lime therefore causes muddy clay 

 water to become clear. The flocks cannot hold water 

 back, and hence limed clay allows water to pass through. 

 Limed clay is also less sticky than pure clay. A clay 

 field or garden is improved by adding lime because the 

 soil does not remain wet so long as it did before ; it is 

 also less sticky and therefore more easily cultivated. 



