1815.} of Dunblane and Pitcaithly. 353 
some have been disposed to decide in the negative, from finding 
-examples of waters possessed of active powers, in which analysis 
does not detect any ingredients of adequate activity. 
_ On the general question, the remark by Dr. Saunders is perfectly 
.Just, that, ‘* considering the comparative accuracy to which che- 
umists are at present able to carry their inquiries, we can hardly 
suppose that, whatever slight error might occur in the estimation of 
minute quantities, the actual existence of any powerful agent on the 
human body in any mineral water should escape the nicety of re- 
search,’ Yet though this is just, and though we can have no hesi- 
tation in rejecting the opinion which would ascribe the medicinal 
qualities of mineral waters to unknown or mysterious causes, or 
which would deny all power to those in which an active chemical 
composition cannot be discovered, difficulties on this subject un- 
doubtedly exist, and there is some room for that scepticism which 
has been extended to this department of the Materia Medica. 
Of this no better example can be given than the celebrated Bath 
water. It has always been found difficult to account for its powers, 
the ingredients which are obtained in its analysis being substances 
of little activity, and the principal ones, indeed, being apparently 
inert. It contains in an English pint, along with a slight impreg- 
nation of carbonic acid, about nine grains of sulphate of lime, 
three grains of muriate of soda, three grains of sulphate of soda, 
sfsths of a grain of carbonate of lime, 4th grain of silica, and ,th 
grain of oxide of iron. Now from these ingredients unquestionably 
no medicinal power of any importance could be expected. They 
are either substances altogether inert, or are in quantities so minute, 
as in the. dose in which the water is taken to be incapable of pro- 
ducing any sensible effect. Some have from this circumstance been 
disposed to deny altogether any virtues to these waters; but the re+ 
verse of this appears to be established by sufficient evidence, and 
what is still less equivocal, the injurious effects they sometimes pro- 
duce, and the precautions hence necessary in their use, sufliciently 
demonstrate their active powers. To account for these, therefore, 
various hypotheses have been proposed. The observation has been 
urged, which to acertain extent is undoubtedly just, that substances 
given in small doses in a state of great dilution may from this dilu- 
tion produce more effect on the general system than the quantity 
iven would lead us to expect. The temperature of the water, too, 
it has been supposed, may have a considerable share in aiding the 
effect; and these two circumstances in particular, it has been 
imagined, may favour the action of the iron. ‘This is the view of 
the subject given by Dr. Saunders, in his Treatise on Mineral 
Waters. Some of the other ingredients, too, it has been supposed, 
may exert unknown powers. ‘hus some effect has been ascribed 
to the agency of the nitrogen gas which rises through the water : 
and Dr. Saunders himself, apparently not very well satisfied with 
the reasoning he had employed, allows some weight to the opinion 
| Soa by Dr. Gibbes, that the siliceous earth assists in the gene- 
or, VI, N° V, Z 
