114 THE VEGETABLE KINGDOM. 



it were not sufficient that the earth should bring forth 

 everywhere all kinds of trees, shrubs, and grasses the waters 

 of the ocean itself are often filled with vegetable life ; in 

 some tracks the tangled sea- weed (Fucus Natans) is so dense 

 as to impede the onward progress of ships for hundreds of 

 miles together. 



Humboldt, in his " Views of Nature," describing the two 

 great banks of sea- weed, says : " The two banks of sea-weed, 

 together with the transverse band uniting them, consti- 

 tute the Sargasso Sea of the older writers, and collectively 

 occupy an area equal to six or seven times that of 

 Germany." 



Nor is this the only vegetation which the great world of 

 waters contains, for if we descend from the contemplation 

 of its larger members we find them even surpassed in 

 quantity by others of such extreme smallness, that they can 

 only be seen individually by means of the microscope, but 

 which exist in such prodigious quantities that the mind can 

 hardly realise the fact. These vegetable atoms have been 

 so increasing and depositing their minute coverings at the 

 bottom of most parts of the ocean, that for hundreds of 

 miles their beds are composed of nothing else, and it has 

 been found that most of the great changes on the surface 

 of the earth have been effected by these minute creatures 

 and their companions of the animal world ; for as we find 

 chalk-downs and coral-reefs formed by the remains of 

 microscopic animals, so productions of equal extent have 

 been formed by the smallest members of the vegetable 

 kingdom, chiefly the " DiatomaceaB," a race of minute vege- 

 table productions which propagate by sub-division and have 

 the power of withdrawing earthy matters from the waters 

 in which they live, which forms a sort of shell or covering ; 

 this shell at their death remains indestructible and gradually 

 accumulates in the bed of the sea (fig. 1). Examination of 

 the various strata of the earth shows that chains of hills, 

 beds of marl, and almost every kind of soil, whether super- 

 ficial or raised from a depth, consist in a great proportion of 

 the earthy remains of these minute plants. These tracts of 

 land were once the beds of oceans which were thus gradually 



