ii 4 4* ANALYSIS of 



tity of water, amounting to about ioo times their own weight, 

 and perhaps more than 200 times their bulk, with which they 

 form a confident jelly, almoft perfectly tranfparent. 



It may be afked here, what prevents the particles of this 

 earth from approaching one another more nearly, and entering 

 into a ftate of ftronger cohefion ? We may, if we pleafe, imagine 

 that they retain round each of them, by chemical attraction, a 

 quantity of water, which forms a little fphere or polyhasdron,with 

 the particle of earth in its centre. Thus, each particle is prevented 

 from coming within a fmaller diftance of the other particles 

 around it, than the diameter of that fphere \ but let the water 

 of thefe fpherules be diminifhed in quantity by evaporation, in 

 confequence of heat, or the attraction of the air, the particles 

 of the earth will immediately enter into a ftate of clofer con- 

 nection and ftronger cohefion, of which we have examples in 

 the exceffive contraction of the jelly, while it is dried up into 

 crufts, and in thofe circles of thin incruftation which were 

 formed on the fides of the glafs-veflels, while the waters were 

 evaporated to drynefs in the firft experiment, the particles of 

 which were fo ftrongly united to one another, and to the fur- 

 face of the glafs, that they coft me much trouble and time to 

 fcrape them off with a knife. 



When fuch a concretion is once formed of this earth, and 

 afterwards receives frequent additions of the fame matter, which, 

 infinuating itfelf into the pores of the concretion, is fixed there, 

 and encreafes its denfity and folidity, the mafs may in time ac- 

 quire a furprifing degree of hardnefs. The petrifactions of 

 Geyzer are undoubtedly formed in this manner, and fome of 

 them are fo denfe and hard that they are fcarcely diftinguifhable 

 from agate or calcedony. 



After making thefe obfervations on the nature of the fili- 

 ceous earth, the proper method for extracting it from the above 

 boiled and neutralized portions of thefe waters, was fuffjciently 

 obvious. I feparately evaporated them to drynefs with a gentle 



beat 



