356 BOTHAMLEY I MINERAL WATERS OF ASKERN IN YORKSHIRE. 
variations have no relation to the variations in the quantity of the 
sulphates. It has also no relation to the chemical reducing power 
of the waters, as measured by means of acidified (potassium) perman- 
ganate solution. 
There can, of course, be practically no doubt that the sulphur- 
etted hydrogen is a product of the reduction of the sulphates present 
in the water. In all probability the magnesium or calcium sulphate 
(or perhaps both) is first reduced to sulphide and the latter is decom- 
posed by the water and carbonic anhydride, with liberation of 
sulphuretted hydrogen. It is well known that sulphates can be 
reduced to sulphides by contact with water and organic matter if all 
air or oxygen is excluded, but we are still in the dark as to the pre- 
cise manner in which the reduction is brought about. 
Sulphuretted water is by no means uncommon in the peat bog 
in which the Askern waters are found, but it seems to occur in 
quantity only in the neighbourhood of the wells now in use. Its 
distribution is very local, and I am informed that sometimes a 
shallow well, cut in the peat, will yield sulphuretted water, whilst a 
similar well only a few yards away will yield non-sulphuretted water. 
Anyone going carefully over the district cannot fail to notice evi- 
dence of the occurrence of sulphuretted hydrogen in the surface 
water at isolated points. 
I was informed that during very hot weather sulphuretted 
hydrogen sometimes appears in one or two of the deeper hollows or 
pits in the Pool, but during my own visits, made at intervals over 
more than two years, including some hot summer months, I never 
saw any evidence of the occurrence of sulphuretted hydrogen in the 
water of the Pool at any point. 
There seems to be no sufficient reason for connecting the forma- 
tion of the sulphuretted hydrogen with the confervoid growth to 
which reference is made by Dr. Lankester in his book, for these 
growths are abundant enough in places where there is no sulphuretted 
hydrogen, although the general character of the water is in other 
respects the same. At the same time all the evidence points to the 
conclusion that the reduction of the sulphates, with production of 
sulphuretted hydrogen, is brought about by some particular kind or 
