164 WHAT IS LIFE? 



upwards to form huge mountains, or pressed down to 

 form deep valleys. Now the water obtains subter- 

 ranean passages in the solid masses of the earth. The 

 water molecules meet with certain molecules, and at a 

 certain temperature they combine, or at any rate 

 produce a compound mass of liquid rock containing 

 water throughout. 1 This mass forces its way into any 

 cracks which may be provided for it by movements of 

 the earth's crust, and often emerges as lava at the 

 surface. Then we may say a volcano is born. 2 



1 See " The Natural History of Lavas as illustrated by the materials- 

 ejected from Krakatoa," Prof. J. W. Judd, F.R.S., Geol. Mag. 1888, 

 p. 10. 



2 The phenomena resulting from contact of molecules may be 

 illustrated by putting a piece of the metal potassium on water ; 

 it immediately decomposes the water, and combustion flame is 

 the result. Or mix some lump-sugar, ground to powder, with 

 potassium chlorate. Dip a glass rod into sulphuric acid, and 

 then touch the powder with the wet rod ; it immediately bursts- 

 into flame almost an explosion. There is a tendency by some 

 to believe that volcanoes are vents for the molten boiling mass of 

 matter beneath the crust of the earth. The evidence that volcanoes 

 are the results of local reaction arising from the contact of water 

 with certain molecular matter, is this : Volcanoes generally exist in 

 the neighbourhood of seas and lakes. When active, there is often a 

 local loss of water, as the failure of wells and springs. Volcanoes, 

 become extinct, showing that the materials for providing chemical re- 

 action have been exhausted. But above all, the enormous amount 

 of water in the vaporous condition steam, ejected by the active 

 volcanoes. It is estimated that 999 parts out of 1000 parts of the 

 white cloud which hangs over an active volcano consist of steam. 

 " It has often been noticed at Vesuvius that each great concussion is 

 accompanied by a huge ball-like cloud of steam Avhich rushes up 

 from the crater. Doubtless it is the sudden escape of that steam 

 which causes the explosion." (" Text-Book of Geology," Sir 

 Archibald Geikie, F.R.S., 3rd edition, 1893, p. 215.) 



Volcanoes belong to almost all geological formations. 



