80 EXISTENCE OF POTASH. 



fresh efflorescence occurs every day. At a 

 celebrated nitre cave, as it is termed, near Na- 

 ples, the efflorescence formed a deposite of one 

 inch in thickness in the course of a few days, 

 and this, too, in constant succession the one de- 

 posite after the other. 



A familiar exemplification of this efflore- 

 scence takes place when Roman cement is 

 used ; the delicate needle shaped crystals 

 which appear on its surface a few days after it 

 has been applied as an external coating prove, 

 that the stone from which this cement is prepared 

 must contain potash, which thus effloresces, 

 and exemplifies the way in which the natural 

 deposites of this salt are produced. 



Spain of all the countries in Europe is said 

 to contain the greatest quantity of nitre in the 

 vegetable soil. Nearly one-third of the uncul- 

 tivated lands in the southern and eastern pro- 

 vinces yielding a rich supply of it when treated 

 in the following manner. During the winter 

 and spring, the land is ploughed two or three 

 times to the depth of two or three inches. It 

 is then allowed to lie fallow until the middle of 

 September when it is lixiviated or washed with 

 water. The liquor is then evaporated down in 

 the usual manner, and deposites a quantity of 

 nitre, mixed however with from thirty to forty 

 per cent, of common salt. 



In Hungary there are several springs and 

 wells so impregnated with this salt as to be 

 quite unfit for drinking, and indeed in almost 

 every soil in every country it exists to a greater 

 or less extent. 



