402 ESSAYS AND OBSERVATIONSi 



I difTolved, in a chopin of fountain- 

 water, vritrioh Mart. gr. xv. and in every 

 ref peel treated it as I had done the Hart- 

 fell fpaw water, viz. it was evaporated 

 over the fire, till thee remained about, 

 two ounces ; this was filtrated, and ex- 

 haled, in a wide glais, before the fire: 

 There was left in the glafs gr, xi//. of a 

 light yellowiih coloured fait, and in the 

 filter a dark brown earth. With this 

 fait, I repeated all the expsriments I had 

 made with the fait of the Hartfell fpaw j 

 and I had the pleafure to fee, that they 

 correfponded in every thing, without any 

 material difference : Only the fait left up- 

 on evaporation of vitriGlum. Murtis did 

 not rife in a blifter on the hot irop, and, 

 \vhen diffolved in water, gave, with pow- 

 der of gall9> a rediih tincture inclining 

 to purple ; whereas the fait of the Hart- 

 fell fpaw, being difTolved in water, with 

 galls, ftruc^ a blue. The reafon of which 

 I take to be, that there is a greater pro- 

 portion of acid in the comppfition of the 

 fait of the Harcfell fpaw, than there is in 

 the 'vifr'tolum Murtis, ; for, if you add an 



alkalij 



