SOIL 19 



and then pour it into a glass vessel. A piece 

 of blue litmus paper should then be put in, 

 and if the paper turns to a red colour, it shows 

 that acid humus is present in the soil, and that 

 lime is necessary to counteract the acidity. 

 More water is then to be added, the whole is 

 to be well stirred, and the muddy water is to 

 be carefully poured off into a large vessel, care 

 being taken that none of the sand which settles 

 at the bottom be lost. The sand is then to be 

 stirred up with fresh water, which is again 

 poured off into the larger vessel. And this is 

 to be done several times until the sand becomes 

 quite clean and free from mud. The contents 

 of the larger vessel are to be allowed to remain 

 for several hours until the fine mud settles to 

 the bottom, when the clear water is to be 

 carefully poured off. The sand and the mud 

 should then be dried and weighed separately, 

 when, by comparing their weights with a quarter 

 of a pound, the proportion of sand and earthy 

 matter in the soil can be ascertained. To dis- 

 cover the presence of lime in a soil, it is only 

 necessary to pour a little hydrochloric acid upon 

 it ; this will cause effervescence if there be any 

 carbonate of lime, and the degree of the effer- 

 vescence will give to an experienced observer 

 a rough indication of the quantity present. To 

 ascertain the exact quantity of lime, however, 

 the acid must be allowed to remain some time 

 on the soil, and then a solution of ammonia 

 must be added. All the lime will, by this 



