solvent by meano of which their rootlets attack succeas- 

 fully the mineral masges of which the soil consists ? If 

 so what are the nature and properties of this solvent? 

 Can such solvents be artificially imitated and can an 

 adequate amount of such solvent so imitated be applied 

 to a known quantity oF soil in question f jr a due time 

 and the solvent thus applied be subsequently 

 examined to see whether the two principles above 

 adverted to have been extracted therefrom and to 

 what extent? How do these amounts tally with the 

 past yield and fertility or otherwise of the soil operated 

 upon ? This investigation, which has been quietly but 

 energetically proceeding for some years, has been 

 answered and has culminated in a most important paper 

 by Dr. Bernard Dyer, read before the Chemical Society 

 in February last and may be very briefly summed up 

 thus :— The solvent in question is root sap present in 

 the rootlets. The result of analysis of more than 100 

 difierent varieties of cultivated plants show that this 

 lootsap is acid and, although varying within tolerably 

 wide limits in the numerous varieties examined, may 

 for practical purposes be fairly represented by a one per 

 cent, solution of citric acid ; an acid very extensively 

 present in plants, as shown by its recent discovery in 

 milk. That when a known amount of soil is agitated 

 with a certain quantity of the artificial sap juice, and 

 for a definite and sufficient time and the separated 

 juice analysed for potash and phosphoric acid there is 

 a close agreement between their amounts and the 

 kncwn fertility, or otherwise of such soil. Above a 

 certain figure fertility is implied, below that amount 

 the reverse. One of the first fields experimented upon 

 was the famous Hooafield at Eothamsted on which 

 barley crops have been grown for 40 years in succession 

 and of which previous records have always been pre- 

 served. By the permission of Sir Henry Gilbert and 

 Sir John Lawes more than 20 samples from as many 

 plots in this field were subjected to this new treatment 

 and with corroborative results not to mention numer- 



