282 PHILOSOPHICAL TRANSACTIONS. [aNNO IJ 17 . 



In order to discover whether Pyrmont waters really contain any purging in- 

 gredients or qualities, I evaporated about a quart of this water ad siccitatem ; I 

 then poured on the reliquiae some rain-water, enough to dissolve and take up 

 the salts, and exhaled that water, and had a grain or two of the salts, that 

 tasted muriatic, such as most river and pump-waters do. It is well known that 

 the purging waters have a very bitter taste, and by Dr. Grew, that salt was 

 called sal catharticum amarum, which distinguished it from all other species of 

 natural salts : that of the Pyrmont water has no relation to this, but rather to 

 the sea-salt, not being in the least bitter.* 



It is also well known, that unless our waters be impregnated with a con- 

 siderable quantity of this bitter salt, it will not purge at all : 2 or 3 grains have 

 not the least cathartic power. For example: Put sij of the purging salts to a 

 quart of common water ; and this quantity will give but a stool or two to one 

 who is naturally very easy to work on. I have examined several other chaly- 

 beate waters, and found much the like ingredients, and never any that I could 

 suspect to carry any purging quality. 



I think we can better demonstrate that the chalybeate waters contain styptic 

 and astringent virtues, because they owe their origin to the iron mineral, and 

 more particularly to the pyrites, which Dr. Lister suggests, (not without some 

 reason) to be the parent even of all iron ores, as it is doubtless the cause of all 

 chalybeate waters: thus I have often examined the solution of the pyrites by 

 the rain-water at Deptford, and at other places where copperas is made, and 

 found it a very strong chalybeate water.-|~ It is from this mineral we have our 

 strong styptic and constringent medicines, for external and internal use ; from 

 hence our powders and salts of steel, or vitriol of mars ; nay, even those ob- 

 stinate and inveterate diarrhoeas which have baffled the force of all medicines, 

 have, by a judicious use of Tunbridge and other iron waters, received a cure. 



But after all we can say, it will be retorted, that there is matter of fact and 

 experience against this, that the waters really do purge at Pyrmont, where they 

 are drank. We allow, that Tunbridge waters do not only purge, but some- 

 times vomit, when drunk hastily, and in great quantity; but our physicians 



* Dr, Slare should have mentioned the weight of tlie residuum which he obtained by evaporating 

 a quart of the Pyrmont water to dryness. His examination was evidently very imperfect. Accord- 

 ing to Bergman's analysis, the Pyrmont waters do contain sulphate of magnesia (the sal catharticum 

 amarum of Dr. Grew) as well as a small proportion of muriate of soda (sea-salt). The other solid 

 and fixed ingredients (besides iron) are carbonate of lime, carbonate of magnesia, and sulphate of 

 lime (selenite). 



f By this action of rain-water upon martial pyrites, there would be obtained a solution of sulphate 

 of iron) i. e. iron combined with the sulphuric acid. But this chalybeate impregnation is different 

 from that of the Spa and Pyrmont waters, in which the iron is combined with the carbonic acid. 



