262 DISCOVERY OF A WHITE FOSSIL POWDER. 
our native Flora is not generally known, it may not be 
amiss briefly to sketch their characters. They are chiefly 
aquatic, and afford the strongest illustration of the fact, that - 
not a spot on the globe has been left without some visible — 
witness of that Almighty hand which first projected it into 
space. If the summit of the most barren rock or exposed : 
heath is clothed with lichens and mosses, scarcely visible 
without a magnifier, the waters also, both salt and fresh, 
swarm with a vegetation of their own, if possible still more | 
minute; the coral caves and deep recesses of the ocean, the - 
crystal lake and stagnant pool, the rapid and the sluggish - 
stream, the pure and ice-cold rivulet of the Alps, the thermal 
waters, and even the boiling Geysers of Iceland, are severally 
provided with plants peculiar to themselves, which would 
soon perish, if transported into any other temperature oF 
locality. "These are the Alge, or Conferve, many of which 
are conspicuous for the beauty and even splendour of their 
colours, and so strange and grotesque in form, that they 
seem to have dropped down from another planet; while each 
is admirably fitted for its place in the great chain of being, 
adapted for food to innumerable tribes of creatures in figure 
as anomalous as themselves, and many of them of direct utility 
to man, either as food, in medicine, or the arts. Some, which 
on account of the simplicity of their forms, are placed at the 
bottom of the vegetable scale, are so minute, as to be invisi- 
ble to the naked eye, except by the altered appearance 
they give to other larger species on which they grow in such 
prodigious numbers. To this division belong those which 
have furnished the fossil powders now described. Their 
figure and structure are so unlike ordinary plants, that some 
of the ablest naturalists have doubted whether they really 
belong to the vegetable world, and have confessed themselves 
unable to draw the line of distinction between them and de 
.. less highly organized animals, from which, however, they are 
equally dissimilar. Minute as they are, many of them secrete 
ard tran parent envelope or shell of pure silex, which, 
^, is almost indestructible, and is composed í 
