163 
As already observed, a certain uniformity prevails through- 
out the springs of this parish, in the nature of the neighbour- 
ing deposits, and the composition of the waters which pass 
through them, whose geological relations are thus rendered 
obvious. 
Let us for one moment illustrate this position by very 
briefly inquiring into the sources of the above ingredients as 
found by analysis. But first, a word or two as to temperature. 
The rains, it is well known, descend irregularly, but during 
the drought of last summer no perceptible change in the 
volume of this spring occurred throughout ; its temperature 
in all the trials, undertaken at various seasons, which I have 
instituted, has been uniformly 48.5 of Fahr., from which it 
may be inferred, that the temperature is imparted by the strata 
through which it flows from some general cause independ- 
ent of solar influences. This may be considered, perhaps, 
inconclusive, since the mean annual heat of the air is not 
stated, nor any computation made as to the rate of absorp- 
tion of caloric by exposed mineral masses, and other circum- 
stances connected with the subject. 
For these investigations we had not time, but it is strongly 
corroborative of internal terrestrial heat, that all the hot 
springs of Britain rise through disturbed strata of the car- 
boniferous system, chiefly below the coal, or through others 
which rest unconformably upon them, the average of seven 
springs afibrding an excess of temperature of 28° above that 
of the atmosphere, and the fact of those which have their 
efflux far distant from volcanic action, as in the Departments 
of the Arrieges and the Pyrenees Orientales, rising in granite, 
just at the boundary of that formation with the slates and 
other stratified rocks. 
But to proceed in tracing the products of this spring as 
furnished by the analysis ; and first, as to the gases. The 
neighbourhood of Horley Green abounds with pyrites, a 
2 A 
