soil. 99 



Why can sandy soils be tilled earlier in the spring than 

 clay ones? Why do the former suffer more in seasons of 

 prolonged drought 1 



Soils as Conductors of Heat. — The construction of a hot-bed, 

 or the setting of a lamp under a pan of germinating seeds, 

 may have attracted attention to the relation between warmth 

 and the growth of plants. To study the part the soil plays 

 in conducting heat, set on a hot stove three similar fruit-cans 

 filled to the same height with dry sand, wet sand, and water 

 respectively. Why does the sand in both cases heat more 

 quickly than the water, and why does the dry sand heat more 

 quickly than the wet ? 



Set on a hot stove cans containing similar quantities of 

 different kinds of soil, all equally dried, to determine the 

 conducting power of each kind. As a test, tablets of lard or 

 soft wax may be laid on the surface of each sample, or 

 thermometers if you have them, or can borrow them, be 

 covered near the surface. Another way is to heat the different 

 samples to the same temperature, then remove them from the 

 fire to learn, with the aid of thermometers plunged in them, 

 which kinds cool the more rapidly. Make further inferences 

 as to the respective advantages and disadvantages of sandy 

 and clay soils, and the value of drainage. 



Acidity and Alkalinity of Soils. — Vinegar is acid. Dip blue 

 litmus paper in it and observe how quickly the paper reddens. 

 Lye is alkaline. Nearly fill a fruit-can, having holes in • the 

 bottom, with hardwood ashes. Pour water on the ashes and 

 allow it to leach through into a tumbler ; pour the water back 

 and let it leach through again. Notice how this lye, in the 

 proportions of about a teaspoonful to a quart, softens hard 

 water as shown when soap is used in it. Dip red litmus in 

 the lye and observe how quickly the paper turns blue. Mix 



