SPECIAL SOIL IMPROVERS 89 



on the soil is totally dissimilar. The great advantages 

 of gypsum lie (i) in the fact that it is a sulphur compound, 

 and sulphur is necessary for the formation of proteins ; 

 (2) that it decomposes sodium carbonate in the soil, and 

 coagulates colloidal clay better than any other substance. 

 When clay has been puddled by excessive application of 

 nitrate of soda, and injudicious working in wet weather, 

 calcium sulphate is an admirable cure. At one time plastering 

 soils was a well-known process, much recommended for the 

 growth of clovers. It has gone out of fashion in the British 

 Isles, but the use of gypsum is still important in many parts 

 of the world, and the experience of the British Isles must not 

 be taken to apply everywhere. The reason why gypsum 

 has gone out of fashion to such a large extent is that calcium 

 sulphate is applied to the soil with other materials. Super- 

 phosphates contain more than half their weight of calcium 

 sulphate. Soils, therefore, that have been liberally treated 

 with super-phosphate are likely to be overcharged with 

 calcium sulphate. Sulphate of ammonia applied in one 

 year of a rotation, and lime applied in another, will produce 

 calcium sulphate in the soil. Owing to the powerful action 

 of gypsum it is still much believed in by some horticulturists, 

 whose duties are often to break up very unsatisfactory land 

 and grow crops with as little delay as possible. Hills 

 composed of little but gypsum occur in some parts of the 

 world, and as it is mined very easily, such local deposits 

 of gypsum should always be carefully considered by those 

 cultivating land at no great distance. 



In the vicinity of large towns sulphur in the form of 

 sulphuric acid is brought down by the rain with the subsequent 

 formation of gypsum in the soil. On the whole gypsum 

 reacts with the soil as an acid whilst lime reacts as an 

 alkali. 



The Use of Electricity in Plant Stimulation. This 

 subject has attracted much attention for many years past. 

 It is such an obvious idea that the original suggesters are 

 probably many in number, but one of the foremost workers 

 in the first days of any substantial results was Professor 



