CHAP. VI.] IVOOD ASHES 159 



salts ill farming until the opening up of the great 

 Stassfurt deposits in Germany. The fertilising value 

 of wood ashes had long been known, and' in the south- 

 east of England it had been customary for the hop- 

 growers to organise a regular system of collection of 

 the ashes of their cottagers, who burned little besides 

 wood, but such a supply was only local and early 

 exhausted. 



William Ellis, again, writing in 1750, states that "at 

 Long Marston, in Bucks, is a potash kiln, where they 

 make ashes from bean straw for the most part, and sell a 

 vat of them, which contains 32 five-bushel sacks, which 

 dresses one acre for fourteen shillings, to be shovelled 

 out of a cart or waggon, and throwed over grass land in 

 this month (July) or at any time till Candlemass." 



In 1 86 1, the output of potash salts began from 

 Stassfurt and rapidly grew, until in 1900 no less than 

 1,158,000 tons were being used for agricultural purposes 

 alone. 



The German potash deposits are situated near the 

 Harz mountains, and centre round the old town of 

 Stassfurt, where for a very long time common salt 

 had been manufactured from natural brine springs. 

 A boring made in 1858 proved the presence of rock- 

 salt at a little more than 1000 feet below the surface, 

 but found above the rock-salt a layer of minerals con- 

 taining potash and magnesia salts, which were at first 

 regarded as worthless but have since become the most 

 valuable substances in the mine, because they constitute 

 the only known source of potash on a large scale. The 

 deposits occur between the Dyas andi Trias formations, 

 and are, therefore, of much the same age as the salt- 

 beds of Cheshire and Worcestershire, and like them 

 they represent the result of the drying up in a hot 

 climate of a great lake or sea, which retained some con- 



