WATERS from ICELAND.- 113 



of the glafs, and the upper furface of which was level and 

 fmooth. I knew the quantity of filiceous earth contained in it ; 

 and comparing this with the weight of the water, when reduced 

 by boiling to gr. 138, I found the proportion of the earth to 

 that quantity of water to be as 2.68 to 1000; and having 

 weighed the jelly by itfelf, the proportion of filiceous earth to 

 the water in it, fuppofing that it contained the whole of the 

 earth, was 10.88 to 1000. In another experiment, in which 

 a fimilar mixture had been lefs boiled, and in which the filice- 

 ous earth bore to the water the proportion of 2.1 or 2. 2' to 100c, 

 I found a foft jelly formed at the end of forty days. And in 

 another, in which the boiling and evaporation was continued 

 until the jelly began to be formed in the upper part of the li- 

 quor while it was boiling, I found the proportion of the filice- 

 ous earth to the remaining water to be nearly as 3.75 to 1000. 



After this jelly is once formed, I never could bring it again 

 into a ftate of diflblution by water alone, whatever quantity of 

 this laft was added. 



It appears therefore by thefe experiments, that when filiceous 

 earth, united with an alkali, is difTolved in 1000 times, or in 

 more than 500 times its weight of water, it will not feparate or 

 fubfide from that quantity of water, although we feparate or 

 difengage the alkali from it. The particles of it, placed at that 

 diftance, do not act on one another by their attraction of cohe- 

 fion or concretion. It is necefTary, in order to enable them to 

 attract one another, that they be brought nearer, by diminish- 

 ing the quantity of the water, until it be lefs than 500 times 

 the weight of the earth. When this is done they will enter 

 into a ftate of cohefion, fooner or later, according as the water 

 has been more or lefs diminifhed. But this ftate of cohefion 

 into which they firft enter, is alfo remarkable. The force of it 

 is exceedingly weak, and it takes place while the particles of 

 the earth are ftill at a considerable diftance from one another. 

 They therefore retain and entangle among them a large quan- 



Vol. Ilf. P tity 



