120 NATURE TEACHING 



established, and at intervals, perhaps once a year, the 

 manured plot should receive a dressing of manure of a 

 vegetable nature. In a school garden a succession of 

 lettuce, beet, beans, and cabbage can readily be grown 

 on the beds. 



Chalk in Soils. 



Carbonate of lime chalk. Place a small piece of 

 chalk in a saucer and pour upon it a little acid, which 

 may be strong vinegar, or hydrochloric acid. Note how 

 it bubbles up, due to its giving off carbon dioxide. 

 Chalk always does this when acted on by an acid, and 

 thus this is a useful test to find out whether a soil 

 contains chalk or not. Repeat the experiment, using 

 small quantities of soil from different places.* From 

 the observations made classify the soils as calcareous 

 and non-calcareous. 



If the surrounding district contains examples of both 

 calcareous and non-calcareous soils, mark their distribu- 

 tion on a map. For this purpose small samples should 

 be collected, by the pupils, from a number of localities, 

 and examined as a class exercise or as a demonstration 

 by the teacher. A map of the district, on a somewhat 

 large scale, may be drawn on stout drawing-paper 

 and hung up in the class-room, or the appropriate map 

 of the Ordnance Survey may be purchased. Observa- 

 tions on the character of the soil may be recorded, from 



* The teacher should provide himself with a collection of 

 soils from different places, taking care to have samples of both 

 calcareous and non-calcareous soils. These samples are preferably 

 kept in bottles. 



