10,2 THE FAIRY-LAND OF SCIENCE. 
in plants, and especially in seeds think of the oils of 
almonds, of lavender, of cloves, and of caraways; and 
the oils of turpentine which we get from the pines, 
and out of which tar is made. When you remember 
these and many more, and also how the seeds of the 
club-moss now are largely charged with oil, you will 
easily imagine that the large masses of coal-plants 
which have been pressed together and broken and 
crushed, would give out a great deal of oil which, 
when made very hot, rises up as gas. You may often 
yourself see tar oozing out of the lumps of soft coal 
in a fire, and making little black bubbles which burst 
and burn. It is from this tar that James Young first 
made paraffin oil, and the spirit benzone comes from 
the same source. 
In the ages that have passed since the vegetation 
that now forms our coal was deposited its slow decom- 
position, perhaps under conditions of great heat and 
pressure, has resulted in vast natural accumulations of 
this coal-oil and also of coal-gas in the interior of the 
earth. 
The great storehouses that contain these valu- 
able products of the ancient coal-forests are only to 
be found where the bending of the strata makes great 
caverns. The rocks and earth above the rocks con- 
stituting the domes over the great natural cisterns or 
tanks often press, as may well be supposed, with enor- 
mous weight upon the inclosed coal-oil or gas. 
When these oil wells, as they are called, were first 
discovered, and before any efficient means of restrain- 
ing the flow had been contrived, the oil frequently 
burst forth, and, carrying away the barriers erected 
