HO W EXTINCT MONSTERS ARE FRESER VED, 1 1 
this “ too too solid flesh would melt ” is soon realised after death ; 
and that active chemical element in the air known as oxygen, in 
breathing which we live, has a tenfold power over dead matter, 
slowly causing chemical actions somewhat similar to those that 
take place in a burning candle, whereby decaying flesh is con- 
verted into water-vapour and carbonic acid gas. Thus we see 
that oxygen not only supports life, but breaks up into simpler 
forms the unwholesome and dangerous products of decaying 
matter, thus keeping the atmosphere sweet and pure ; but in 
time, even the dry bones of the bird or rabbit, though able for 
a longer period to resist the attacks of the atmosphere, crumble 
into dust, and serve to fertilise the soil that once supported 
them. 
Now, if water and air be excluded, it is wonderful how long 
even the most perishable things may be preserved from this other- 
wise universal decay. In the Edinburgh museum of antiquities 
may be seen an old wooden cask of butter that has lain for 
centuries in peat — which substance has a curiously preservative 
power ; and human bodies have been dug out of Irish peat with 
the flesh well preserved, which, from the nature of the costume 
worn by the person, we can tell to be very ancient. Meat packed 
in tins, so as to be entirely excluded from the air, may be kept a 
very long time, and will be found to be quite fresh and fit for use. 
But air and water have a way of penetrating into all sorts of 
places, so that in nature they are almost everywhere. Water can 
slowly filter through even the hardest rocks, and since it contains 
dissolved air, it causes the decay of animal or vegetable sub- 
stances. Take the case of a dead leaf falling into a lake, or some 
quiet pool in a river. It sinks to the bottom, and is buried up 
in gravel, mud, or sand. Now, our leaf will stand a very poor 
chance of preservation on a sandy or gravelly bottom, because 
these materials, being porous, allow the water to pass through 
them easily. But if it settles down on fine mud it may be covered 
up and become a fossil. In time the soft mud will harden into 
