68 
THE PHYSICAL GEOGRAPHY OF THE SEA. 
supply of food designed for living creatures is thrown ; or, in one 
word, it is itself the food, in its simple form, of all living crea- 
tures. The animal grinds down the fibre and the tissue of the 
plant, or the nutritious store that has been laid up within its cells, 
and converts these into the substance of which its own organs are 
composed. The plant acquires the organs and nutritious store 
thus yielded up as food to the animal, from the invulnerable air 
surrounding it." 
" But animals are furnished with the means of locomotion and 
of seizure — they can approach their food, and lay hold of and 
swallow it ; plants must wait till their food comes to them. No 
solid particles find access to their frames ; the restless ambient 
air which rushes past them loaded with the carbon, the hydrogen, 
the oxygen, the water — every thing they need in the shape of sup- 
plies is constantly at hand to minister to their wants, not only to 
afford them food in due season, but in the shape and fashion in 
which alone it can avail them." 
90. There is no more worthy or suitable employment of the 
human mind than to trace the evidences of design and purpose 
in the Creator, which are visible in many parts of the creation. 
Hence, to the right-minded mariner, and to him who studies the 
physical relations of earth, sea, and air, the atmosphere is some- 
thing more than a shoreless ocean, at the bottom of which his 
bark is wafted or driven along. It is an envelope or covering for 
the dispersion of light and heat over the surface of the earth ; it 
is a sewer into which, with every breath we draw, we cast vast 
quantities of dead animal matter ; it is a laboratory for purifica- 
tion, in which that matter is recompounded, and wrought again 
into wholesome and healthful shapes ; it is a machine (§ 87) for 
pumping up all the rivers from the sea, and conveying the waters 
for their fountains on the ocean to their sources in the mount- 
ains. 
91. Upon the proper working of this machine depends the well- 
being of every plant and animal that inhabits the earth ; there- 
fore the management of it, or its movement, or the performance 
of its offices, can not be left to chance. They are, we may rely 
upon it, guided by laws that make all parts, functions, and move- 
ments of the machinery as obedient to order as are the planets in 
their orbits. 
