_Experiment_ 1. Some pieces of galls being added to equal quantities of the water of the two springs, an exceeding deep and bright blue colour was immediately produced in the water of the upper spring, which in a little time turned to a perfect black. The water of the lower spring, tho’ indeed it was turned of the same colour, yet was not of so deep a shade, but was somewhat lighter than the former. The tincture of galls caused the same appearances. 2. A tincture of balaustine-flowers produced the above blue colours in both waters. 3. A quantity of the water being thoroughly tinged with galls, was allowed to stand 24 hours: being then filtrated thro’ brown paper, the water, tho’ almost quite colourless, would not again receive any tincture with galls. 4. After elixation the water became of a turbid yellow colour with ochre, and afforded very little tincture with galls. 5. A solution of sal Martis, chemically prepared, being mixed with galls, immediately turned of a bright dark blue colour, exactly similar to that produced in the water. 6. A solution of common and rock alum was no-ways changed in its colour with galls. 7. A solution of sal Martis and alum being mixed in equal quantities, the mixture was turned of a bright blue colour with galls; yet not of so deep a hue, but of a more diluted colour than the solution of sal Martis, without alum. From these experiments we must first of all observe, that the colour, which these waters afford with galls and pomegranate-flowers, is very uncommon. The more iron, that any mineral water contains, it will afford the deeper colour with such astringents: but tho’ I have tried this experiment upon a great many of the ferrugineous waters in Scotland, and also upon the waters of some of the foreign Spaws, I never observed one, that afforded so deep a colour as this, which we now consider. Some of the weakest of them gives only a red or faint purple tincture, and the strongest only a deep purple: but I never saw or heard of any chalybeat water, but this, either in Scotland or elsewhere, that afforded an intense black and inky colour with galls. From which, I think we may venture to conclude, that the water of this Spaw contains a far larger proportion of iron than most, or perhaps than any, other chalybeat water hitherto discovered: and for this reason, I dare say, it will likewise be so much the more preferable to most others in medicinal virtues; which has indeed already appeared by many surprising cures it has performed, and which, I am persuaded, will more fully appear, when its medicinal effects shall be better known.