THURSDAY, JANUARY 9g, 1873 
DEEP SPRINGS 
S our contribution to a controversy which has now 
been going on for some weeks in the 77mes, and 
to which much public attention has been given, we have 
received Prof. Geikie’s permission to print a Lesson 
from his forthcoming Primer of Physical Geography 
dealing with the subject of Deep Springs. 
The facts which Prof. Geikie here summarises in so 
admirable a manner, taken in connection with what has 
already appeared in NATURE as to what one may almost 
call the cosmical connections of the recent rainfall, and 
the actual conditions of the case placed before the 
readers of the Zzmes by Mr. Bailey Denton, should, we 
think, be enough to convince all that there is a science in 
these matters, and that the way in which Nature is in the 
habit of working should be at least understood, if even in 
only a feeble way, before a protest be entered against 
her. 
Do we wish to continue to avail ourselves of surface 
springs? If so it must be remembered, first, that these 
are impossible without the deep springs of which Prof. 
Geikie speaks ; secondly, that it may be roughly said, 
that they are normally replenished once a year, and that 
in some parts of England there has not been rain enough 
this year yet to replenish them. In the words of Mr. 
Denton :— 
“During the summer months, from May to October, 
the rain which falls seldom reaches the depth of a yard. 
This has been clearly shown by Dickinson’s records. 
During that period evaporation, exceeding the rainfall 
very considerably, draws upon the subterranean supply of 
water stored in the soil, and in continued drought the 
draught is immense. In the winter months, from October 
to May, when the rainfall exceeds the evaporation, the 
excess penetrates the earth, and having saturated the 
subsoil as it passes through it, the surplus descends to 
the springs or subterranean level to replenish the one and 
raise the other. To produce this super-saturation requires 
time, and hence it is that ‘mid-winter’—ze. the shortest 
day—is reached before the deep springs and deep water- 
beds are augmented.” 
The present controversy will do lasting good if it 
induces, and we think it may, accurate observations of 
the amount of water in the deep springs in different 
areas in different years, and at different times of the 
year. Itis more than possible that the late heavy rainfall 
is even, from the deep spring point of view, a manifesta- 
tion of a higher law—or ofa miracle as Mr. Babbage would 
have called it—that nature may not only replenish our 
underground cisterns every year, but vary the yearly 
supply, over a period of eleven years or so. 
Professor Geikie’s “ Lesson” runs as follows :— 
“Tn this lesson we are to follow the course of that part 
of the rain which sinks below ground. A little attention 
to the soils and rocks which form the surface of a 
country is enough to show that they differ greatly from 
each other in hardness, and in texture or grain. Some 
are quite loose and porous, others are tough and close- 
grained. They consequently differ much in the quantity 
No. 167—VOL, VII 
NATURE 
Lai 
of water they allow to pass throughthem. A bed of sand, 
for example, is pervious, that is, will let water sink 
through it readily, because the little grains of sand lie 
loosely together, touching each other only at some points, 
so as to leave empty spaces between. The water readily 
finds its way among these empty spaces. In fact, the 
sand-bed may become a kind of sponge, quite saturated 
with the water which has filtered down from the surface. 
A bed of clay, on the other hand, is impervious; it is 
made up of very small particles fitting closely to each 
other, and therefore offering resistance to the passage of 
water. Wherever such a bed occurs, it hinders the free 
passage of the water, which, unable to sink through it 
from above on the way down, or from below on the way 
up to the surface again, is kept in by the clay, and forced 
to find another line of escape. 
“ Sandy or gravelly soils are dry because the rain at 
once sinks through them ; clay soils are wet because they 
retain the water, and prevent it from freely descending 
into the earth.. 
“When water from rain or melted snow sinks below 
the surface into the soil, or into rock, it does not remain 
at rest there. If you were to dig a deep hole in the 
ground you would soon find that the water which lies 
between the particles would begin to trickle out of the 
sides of your excavation, and gather into a pool in the 
bottom. If you baled the water out it would still keep 
oozing from the sides, and the pool would ere long be 
filled again. This would show you that the underground 
Mice will readily flow into any open channel which it can 
reach. 
“Now the rocks beneath us, besides being in many 
cases porous in their texture, such as sandstone, are 
all more or less traversed with cracks—sometimes 
mere lines, like those of a cracked window-pane, but 
sometimes wide and open clefts and tunnels. These 
numerous channels serve as passages for the under- 
ground water. Hence, although a rock may be so 
hard and close-grained that water does not soak through 
it at all, yet if that rock is plentifully supplied with these 
cracks, it may allow a large quantity of water to pass 
through. Limestone, for example, is a very hard rock, 
through the grains of which water can make but little 
way ; yet itis so full of cracks or ‘joints,’ as they are 
called, and these joints are often so wide, that they give 
passage to a great deal of water. 
“Tn hilly districts, where the surface of the ground 
has not been brought under the plough, you will 
notice that many places are marshy and wet, even 
when the weather has long been dry. The soil every- 
where around has perhaps been baked quite hard by 
the sun; but these places remain still wet in spite of 
the heat. Whence do they get their water? Plainly not 
directly from the air; for in that case the rest of the 
ground would also be damp. They get it not from above, 
but from below. It is oozing out of the ground ; and it 
is this constant outcome of water from below which keeps 
the ground wet and marshy. In other places you will 
observe that the water does not merely soak through the 
ground, but gives rise to a little runnel of clear water. 
If you follow such a runnel up to its source, you will see 
that it comes gushing out of the ground as a Spring. 
“Springs are the natural outlets for the underground 
water. But you ask why should this water have any 
outlets, and what makes it rise to the surface ? 
“The subjoined figure (Fig. 1) represents the way in 
which many rocks lie with regard to each other, and 
in which you would meet with them if you were to 
cut a long deep trench or section beneath the surface. 
They are arranged, as you see, in flat layers or beds. 
Let us suppose that @ is a flat layer of some imper- 
vious rock, like clay, and 4 another layer of a porous 
material, like sand. The rain which falls on the sur- 
face of the ground, and sinks through the upper bed, 
L 
