350 OLIVER: MINERAL SPRINGS OF THE WEST RIDING. 
for whether a mineral spring shall bring- these constituents, present 
in the formations whence it is derived, to the surface, is a matter 
determined by the sulphates encountered as the water rises to its 
issue. In giving due weight to this fact we must bear in mind that 
in Harrogate the greatest care has been taken, especially in recent 
years, to exclude by water tight wells, etc., the inlets of surface 
water which generally contain sulphates. But even here it has been 
found that a newly opened well will deliver a sulphate-holding water 
for a certain time, which may at last become sulphate free. There 
are besides those of Harrogate many sulphate-free brine waters 
which contain barium and strontium: such, for example, as the 
mineral water issues from the coal formation of the Alleghany River 
district, and several of the Canadian waters described by Dr. Hunt.§ 
The frequent occurence of barium carbonates (witherite) along with 
the metallic sulphides in the lower carboniferous rocks, appears to 
be the only geological fact, at present known, suggestive of an 
explanation of the barium impregnation. 
4. Protoohloride of Iron. 
The appearance of this salt in large quantity in the Imperial 
Chalybeate Saline water — perhaps the most remarkable mineral 
spring in Europe — is a chemico- geological curiosity, and notwith- 
standing the valuable analytical evidence provided by several eminent 
chemists, it remains a puzzle to those who attempt an explanation of 
its origin. Is it derived from chemical decomposition, or from some 
existing deposit ? 
(1) Chemical decomijosition. — The only probable reaction is that 
between iron sulphate and barium chloride, which yields ferrous 
chloride and barytes. 
Fe SO4 + Ba Cl^ = Fe CI^ + Ba SO4. 
I have pointed out the fact that on the Bogs-Field iron sulphate 
is generated by oxidation of iron sulphide ; may there not be a 
similar convertion, hitherto unobserved, going on in the neighbour- 
§ The saline water of Boston Spa on the Pennian beds, about 12 miles 
S.E. of HaiTogate, is also sulphate free, and contains barium. See Contributions 
to the History of the Mineral Waters of Yorkshire, by Prof. Thorpe, F.R.S. The 
close familj' likeness of this water to the Harrogate Salines points to a similar 
source in the carboniferous beds that underlie the permian formations in this 
locality. 
