186 THE EARTH CONDUCTS SOUND. 
and I have often been astonished to see that grass 
plots and fields had advanced greatly in growth 
during the period they had thus lain concealed 
from view. But, not only are grasses providentially 
resistent of frost, they resist great heats also, 
their tops may indeed wither, and we may fancy 
they are sacrificed, but the roots retain vitality and 
take the first occasion to throw forth new shoots. 
Again, the graminez thrive well, at least the 
majority of the species, in every variety of soil, and 
hence, gardeners need be no longer astonished at 
the trouble they encounter in freeing their grounds 
of grass weeds, the vast number of seeds sown by 
one plant is astonishing, and if buried by the spade 
after being thus scattered, other seeds of the same 
order are brought to light by the act of spading, and 
those then buried will in their turn be exposed to 
the surface at a future time. The cerealia grow in 
most climates and situations as though they were 
designed for the especial consumption of man, the 
cosmopolite. 
There is one fact which illustrates with us the 
power of the earth in conducting sound. When 
every thing around is still, and particularly there- 
fore at night, a hollow roaring sound reaches the 
ear from the direction of the rocky coasts. On 
paying more attention, we find there are intervals 
regularly kept when the noise is much less evident, 
perchance proceeding from echo of what had just 
died away. Attending to the phenomenon with 
greater accuracy still, it is remarked that the noise 
is more plainly heard in vallies than on elevated 
spots, and lastly it is perceived only when the wind 
arrives from the direction of the coasts, and especi- 
ally from the south-west. It is caused by the 
continued and reiterated blows inflicted by the tide 
upon the rocks and precipices of the shore. It may 
