688 CONTiUBUTION.S TO OUU KNOWLEDGE OF SOIL-FERTILII Y, iv., 



phuretted hydrogen, and sodium thiosulphate. Some of these, 

 as copper sulphate, were themselves toxic, while the others, 

 as superphosphate, simply acted as stimulants after the man- 

 ner of magnesium and potassium sulphates, as already noted. 

 The only salt that gave any promise of possessing any degree 

 of antitoxic power, was sodium thiosulphate, and it was 

 further investigated. The following four experiments are 

 given as showing the general result in solutions of the extract, 

 and in the soils themselves. 



Experiment vii. 



