Analyfis of Earths and Stones*. 1 61 



blue be reddened, an acid exifts in the diftil- 

 led liquid ; if the red be effaced, and the blue 

 reftored, a volatile alkali is the caufe of it : 

 if the liquor precipitates lime water, but does 

 not precipitate nitrous felenite, then it con- 

 tains fixed air : if it precipitates alfo nitrous 

 felenite, it contains the vitriolic acid : if it 

 contains the marine acid, it will not precipi- 

 tate nitrous felenite, but it will the nitrous 

 folution of filver: The lofs of weight of 

 the refiduum in the retort, and the weight of 

 the water in the receiver, will {hew the pro- 

 portion of the volatile ingredients. 



\ 



Another portion fhould be digefted in about 

 6 or 8 times its weight of pure water, and 

 the properties of that water examined, to 

 find whether the Earth contains neutral falts. 

 Here the method given by Mr. Bergman in 

 his analyfis of mineral waters, fhould be fol- 

 lowed. 



SECTION II. 

 Of the general Examination of Stones. 



Their fpecific gravity fhould firft be exa- 

 mined; alfo their hardnefs ; whether they 

 will ftrike fire with fteel, or can be fcratched 

 by the nail, or only by cryftal or ftones of ftill 

 greater hardnefs 3 alfo their texture, perviouf- 



M nefs 



