( ^7^ ) 
a faint reddi(h Colour with Powder of Galls (as the Vi- 
trioUc Waters of TunhridgCy Aftrop^ and divers others do, 
and as you fee it has in fome Meafure done in the Ex- 
ample here before you) it not only led me to believe 
that thefe Waters, fbme of them, might as well iflue from 
Slat as an Iron Oar ; unlefs it Ihould appear, that this 
fort of Slat were an Iron Oar too, which put me upon 
calcining it for Three or Four Hours after the manner of 
Dr. Lijler, to experiment, whether it would then (like 
the other Iron Oar) apply to the Magnet; wherein iho* 
I was altogether unfuccefsful, the Magnet not taking the 
leaft notice of it, yet it afforded me another Difcovery 
altogether as fatisfacflory, which is the Mauer I have at 
prefent to communicate to you ; viz. That upon Tor- 
refaftion it was all become a Yellow Ochre, and would 
fcore like it ; tho' this here I have to (hew you, be grown 
a little too dark by much burning, which further per- 
fwades me, that the Yellow, or rather Orange- coloured 
Sediment we find at the Bottom of thefe Fountains,comes 
rather from this fort of Slat, than an Iron Ore for I 
much queftion whether fome of the Yellow Ochres (tho' 
it's plain the Red ones do) come from, or are, Iron Ores ; 
but I intend to calcine this further the next Week, where- 
of you (hall have an Account the next Meeting, but 
doubt of my Succefs, becaufe the Shotover Yellow 
Ochre will not own the Magnet after Thirty.fix Hours 
Calcination, or better. 
IL Some 
