Introduction xiii 



The pot experiments of Chaps, vi., vii. and viii. 

 should be started as early in the course as possible. 

 Twenty flower pots are wanted for the set ; they should 

 be of the same size, about eight inches being a convenient 

 diameter, and should be kept together in a warm place. 

 Three are filled with sand, seven with subsoil, and the 

 remaining ten with surface soil Three of the subsoil 

 pots are uncropped, two being stored moist and one 

 dry. Four pots of the surface soil are uncropped and 

 moist, a fifth and sixth are uncropped and dry, one of 

 these contains earthworms (p. 54). Four glazed pots, 

 e.g. large jam or marmalade jars, are also wanted (p. 69). 

 Mustard, buckwheat, or rye make good crops, but many 

 others will do. Leguminous crops, however, show certain 

 abnormal characters, while turnips and cabbages are apt 

 to fail : none of these should be used. It is highly 

 desirable that the pots should be duplicated. 



The plots also should be started in the school garden 

 as early as convenient. Eight are required for the set : 

 their treatment is described in Chap. ix. Plots two 

 yards square suffice. 



A supply of sand, of clay, and of lime will be wanted, 

 but it is not necessary to have fresh material for each 

 lesson. The sand may be obtained from a builder, a sand 

 pit, the sea shore or from a dealer in chemical apparatus. 

 The clay may be obtained from a brick yard; it gives 

 most satisfactory results after it has been ground 

 ready for brick making. Modelling clay is equally satis- 

 factory. A supply of rain water is desirable. 



For a class of twelve children working in pairs at 

 the experiments the following apparatus is wanted for 

 the whole course : — 



