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its dark colour. The Argillaceas, v/Iien' mixed 
with lime, melt by themfelves, as above-men- 
tioned ( I.). When mixed with iron, as in the • 
Boles, they grow dark or black ; and if the iron 
is not in too great a quantity, they melt alone inta 
a dark flag *, the fame happens, when they arc 
mixed with iron and a little of the vitriolic acid» 
as in the common clay, &c. 
5. The Micacece and Afbeftinse become fomc-^ 
what hard and brittle in the fire, and are more or 
lefs refradtory^ though they give fome marks of 
fufibility. 
6. The Fluores difcover one of their chief cha- 
rafteriftics by giving a light, like Phofphorus,. in - 
the dark, when they are flowly heated ; but lofe 
this property, as well as their colour, as foon as 
they are made red hot : They commonly melt ia 
the fire into a. white opaque flag, though fome of 
them not very eafily. 
7. Some forts of the ZcoUteSy a ftone lately dif- 
Gcvered, melt eafily and foam in the fire,, fomc- 
timcs nearly as. much as Borax, and become a 
frothy flag, &c. 
8. A great many of thofe mineral bodies- which 
are impregnated with iron, as the Boles, and fome 
of the White Iron Ores, &c. as well as fome of 
the other iron ores, viz. the Bloodftone, are not 
at traded by the loadflone before they have been 
thoroughly roafled, &c, 
A further digrefTion upon thefe effeds is un- 
necefifary here, their enumeration belonging more 
properly to the Mineralogy •, it is fufiicient only 
to have mentioned the moft common, in order the 
better to explain the experiments that are made 
with the Blow-pipe. 
SECXr 
