178 
will be arrested by the lower one, and made either to 
gather there, or find its escape along the surface of that 
lower bed. If a hollow orvalley should have its bottom 
below the level of the line along which the water flows, 
springs will gush out along the sides of the valley, as 
shown at ssin the woodcut. The line of escape may be 
either, as in this case, the junction between two different 
kinds of rock, or some of the numerous joints already 
referred to. Whatever it be, the water cannot help flow- 
Fic. 1.—Origin of Surface Springs. 
ing onward and downward, as long as there is any passage 
by which it can find its way ; and the rocks underneath are 
so full of cracks that it has no difficulty in doing so, 
“But it must happen that aj great deal of the under- 
ground water descends far below the level of the valleys, 
and even below the level of the sea. And yet, though it 
should descend for several miles, it conigs at last to the 
surface again. To realise clearly how this takes place, 
let us follow a particular drop of water from the time when 
it sinks into the earth as rain to the time when, after a 
long journeying up and down in the bowels of the earth, 
it once more reaches the surface. It soaks through the 
soil together with other drops, and joins some feeble 
Fic. 2.—Section of part of a district to show the origin “of deep-seated 
Springs. The Numerous joints in the rocks lead the water down into a 
main channel, by which it re-ascends to the surface as a spring at s. 
trickle, or some more ample flow of water, which works 
its way through crevices and tunnels of the rocks, It 
sinks in this way to perhaps a depth of several thousand 
feet until it reaches some rock through which it cannot 
readily make further way. All this while it has been fol- 
lowed by other drops, coursing after it through its wind- 
ing passage down to the same barrier at the bottom. The 
union of all these drops forms an accumulation of water, 
which is continually pressed by what is descending from 
the surface. Unable to work its way downward, the pent- 
up water must try to find escape in some other direction. 
By the pressure from above it is driven through other 
cracks and passages, winding up and down until at last it 
comes to the surface again. It breaks out there as a 
gushing spring (see Physics Primer, Art. 23). 
“Thus each of the numerous springs which issue out of 
the ground is a proof that there is a circulation of water 
underneath, as well as upon the surface of the land, But 
besides these natural outlets, other proofs are afforded by 
the artificial openings made in the earth. Holes, called 
asyee Pad. . ce eee ae ee fi 
CORES Ri ny 5) ae ae ae 
NATURE ss) ‘[Fan. 9, 1873 
Wells, are actually dug to catch this water. Mines, pits, 
quarries, and deep excavations of any kind, are usually 
troubled with it, and need to be kept dry by having it 
pumped out.” 
It is a satisfaction to think that,as Science gets more 
infused into our general education, such a question as — 
the one to which attention is now directed will not be 
mooted until its scientific bearings’ are understood ; for 
after all the question of deep springs is only one of the 
scientific points involved in the controversy. 
SHELLEY'S BIRDS OF EGYPT 
A Handbook to the Birds of Egypt. By G. E. Shelley, 
F.G.S., F.Z.S., &c. 1 vol. 8vo, with 14 coloured plates. 
(London: Van Voorst, 1872.) 
LY, Nie travellers who go “up the Nile” during the 
4 winter months, devote the leisure, which would 
otherwise hang somewhat heavily on their hands, to 
making a collection of birds. The boating trip usual on 
these occasions is, as Captain Shelley observes, admirably 
adapted for this purpose, “as there is much time left on 
hand while the vessel is delayed by adverse winds ; and 
even at other times progress is frequently not so rapid as 
to prevent the traveller from keeping pace with the boat, 
if he chooses to land for the sake of sport, which may 
generally be obtained on the banks of the river,” 
To such persons Captain Shelley’s volume w:i! | e most 
acceptable, as there was previously no single work that 
contained sufficient information to enable them to deter- 
mine the names of the birds met with on the Nile. Riip- 
pell’s “ Systematische Uebersicht” gives a complete list of 
all the species known to occur in Egypt at the time of its 
publication. But besides being now rather out of 
date, Riippell’s volume does not include descriptions 
of most of the common birds, and requires to be sup- 
plemented by several other works hardly adapted for 
a traveller’s library. Captain Shelley’s handy volume 
contains a sufficiently full account of all the Egyptian 
birds hitherto recorded, and is therefore far more conye- 
nient for use during a tour up the Nile, though other 
works will be required on the return home, to enable some 
of the more closely allied species to be certainly dis- — 
criminated, 
As limits of the “ Egyptian district,” of which he treats, 
Captain Shelley takes the Mediterranean on the north, 
and the second Nile cataract on the south, with the Ara- 
bian and Libyan deserts to the east and west. Within 
this area about 350 species of birds are met with, of each 
of which a short description is given, together with remarks 
upon the time of its occurrence, habits, and other pecu- 
liarities. The greater number of the birds of Egypt are 
well-known European forms, but there is a considerable 
admixture of Oriental and African speciés. In the latter 
category we may notice the beautiful little sun-bird, Vec- 
tarinia metallica, of which the portrait forms the 
frontispiece to the volume. Captain Shelley met with it 
near Kalabshee in Nubia, where it is tolerably plentiful in 
April, but has “no doubt that it occasionally descends 
below the first cataract,” as he noticed several specimens 
within twenty miles of Philee, Other tropical forms which 
