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doubtedly purer and more wholesome for drinking purposes than 
the always more or less contaminated waters of surface springs, 
rivers or lakes. 
We hear a good deal about our coal supplies becoming exhausted, 
so it is consoling to hear from America that the coalfields of that 
country alone are sufficient to supply the whole world for some 
2000 years longer. No doubt the apparently inexhaustible supplies 
of petroleum recently discovered in Russia, and which are brought 
through wooden pipes some 500 miles to the seaboard, will furnish 
a cheap substitute for solid fuel in the immediate future. Petroleum 
has been recently used, not only for smelting operations, but as a 
substitute for steam in propelling vessels. These ships have 
neither paddle-wheels nor screw, but carry a large tank containing 
petroleum, which is conducted in small charges along a steel pipe 
which opens in the stern of the vessel just below the water-mark. 
It is here mixed with atmospheric air to render it explosive, and 
each charge is fired in quick succession by electricity. The force 
of the explosion being expended on the water astern is sufficient 
to propel the vessel at the required speed. A practical step in the 
direction of utilising the internal heat of the earth has been made 
at Pesth, where a well has been sunk to 8,000 or 4,000 feet in 
depth and water raised at 180 degrees of heat, a temperature at 
which most culinary operations can be conducted. I have myself 
cooked food in water thus heated at the geysers, the celebrated 
boiling springs in Iceland. Whether this means of obtaining heat 
would pay is extremely doubtful; it would bea question of the 
relative expense of very deep boring or raising of coal. As the 
thickness of the earth’s solid crust is variously estimated at from 10 
to 400 miles, it would in no case be a very easy engineering task to 
tap the intensely hot fluid matter of the earth’s interior, or even to 
reach a depth at which we might theoretically expect to find a 
temperature of 212 degrees. The interesting experiments lately 
made by M. Spring, of Liege, seem to prove that all matter 
becomes fluid under extreme pressure, even metals flowing like 
water under a pressure of 750 atmospheres. These facts seem to 
settle the vexed question as to the solid or fluid condition of the 
earth’s centre, since, ifthe hardest metals become fluid at a pres- 
sure of 700 or 800 atmospheres, which would obtain at a depth of 
12 miles below the surface, no imaginable rock could remain 
solid at the inconceivable pressure which much exist at 2,000 miles 
of depth. 
They are making great progress with the celebrated Lick Obser- 
vatory in California. The great telescope, with the large 8ft. 
refractor, is at last finished, having cost £100,000. It is now 
proposed to provide a wonderful automatic apparatus. ‘‘ On enter- 
