148 REPORT—1883. 
directing public opinion to the value of such supplies, and by the pre- 
servation of the records of those carried out, has given an impetus to water 
of this class being generally adopted for domestic consumption in districts 
where gravitation supplies are unsuitable or unattainable. 
As regards the first head of inquiry—the circulation of underground 
waters—much remains to be learnt, especially as to the influence of 
variation of barometrical pressure on the volume of springs. Indepen- 
dent investigation is now being carried on by Mr. Baldwin Latham, but 
it is exceedingly desirable that numerous observations should be taken 
in different classes of rocks, the quantity of water a rock is capable of 
holding being no measure of the quantity of water it is capable of yield- 
ing. The difference of the period of time in which two rocks will absorb, 
and give off by gravity, the same quantity of water is governed by the 
difference of their chemical composition. 
The chemical composition of two rocks being identical, their facility 
of discharge of water is in direct relation, to the amount by which they 
are traversed by planes of joints and fissures, and the extent these may 
run parallel or at right angles to the valleys which cut into and expose 
the water-bearing beds. 
The proportion of the annual rainfall that is absorbed by different 
classes of rocks is a subject that requires further examination. The 
quantity is largely regulated by the quantity stored from previous years. 
After a succession of dry years the permanent water-level is reduced to 
minimum figures, and the water gradient becomes nearly flat and springs 
cease to flow. The first heavy rains will be nearly wholly absorbed, until 
the maximum water-gradient is reached and the rocks are stored with 
the largest amount of water they can hold. After they are once charged, 
all excess of rainfall runs off in floods, and the amount absorbed is prac- 
tically nil. Spread over the twelve months, the annual amount absorbed 
is probably never more than 15 inches, and the average ranges from 
5 inches in chalk countries to 10 inches in new red sandstone areas. 
In millstone grit districts about 8 inches are absorbed, but the permeable 
beds are thin, and the water is thrown off again in numerous springs, as 
a rule in the same drainage basin, giving permanence to the dry-weather 
flow of the streams traversing them. Except in Waterworks drainage 
areas but few observations exist as to the actual volumes run off daily © 
by the rivers of this country, and data on this subject are much required, 
as well as a permanent record of the height to which floods rise in the — 
various river-basins. 
Farther observations are required as to the action of faults in acting 
as ducts, along the face of which water is constantly passing, and barriers 
separating districts into distinct drainage areas. The facts so far obtained 
point to faults traversing thick permeable sandstone and limestone, having 
these formations on both sides of the dislocation, as offering no obstacle 
to the free passage of waters, which, even if locally obstructed by the 
hardened face or slickenside jointing of the fault, invariably finds its way 
through cracks extending across the width of the fault. In faults traversing 
thick shales and clays of any age, the fissure, be it wide or narrow, always. 
appears to haye been filled with the impermeable material forming the 
sides, and in some cases, when porous rocks have been immediately over- 
lain by impermeable material since denuded, the fissure of the fault has 
been filled from above at a time when the fault had an upward prolonga- 
tion, destroyed with the above-mentioned denuded material. 
