620 KANSAS ClTY REVIEW OF SCIENCE. 
basin where the waters may be retained for a time. But should there be an 
excess of decomposing vegetation present, as in peat bogs, this reoxidation can- 
not take place, and the metal is deposited in the form of carbonate of iron. The 
former of these methods is the more usual, though the latter is not infrequent. 
But the existence of iron ore in either of these forms proves the existence of veg- 
etation at the time of its accumulation. Now, the Laurentian period was remark- 
able for the extensive beds of iron ore that were accumulated in its rocks. The 
vast deposits of iron found in the Iron Mountain regions of Missouri, the Lake 
Superior regions of New Jersey, and Sweden, all are found in the rocks of this 
period. Now, taking the above facts, either singly or in combination, they seem 
to establish beyond a doubt the existence, even during this time, of enormous 
quantities of vegetation, although not a vestige of it may exist in the form of 
fossils at the present time. The fact of the disappearance of all these organic 
forms may be easily accounted for in the extremely fragile character of all those 
primitive organisms. And while the above are only circumstantial evidences of 
their existence, they.are of such a nature as to carry all the weight that belongs 
to ordinary direct evidence. We conclude, therefore, that the existence of lime- 
stones, graphite and iron, in the rocks of the Laurentian period, prove the 
existence of vegetation during the time of their formation, while the enor- 
mous extent of their existence is to be taken as the measure of its abundance. 
While we are thus positive of the existence, during the early period, of vast 
quantities of vegetable matter, in regard to the form in which it flourished we are 
left entirely to conjecture. But of one thing we are assured, and that is that no 
land plants existed at that day, for the very good reason that no dry land had yet 
appeared above the universal ocean that covered all the face of the whole earth, 
and consequently this class of vegetation could not have had any influence in 
bringing about the above results. All the vegetation of that age was doubtless 
of that simple yet extensive class of marine plants known as fucoids. The 
Archzean age, of which we have been treating, was followed by the Silurian ; 
but, between the closing of the former and the beginning of the latter, there 
seems to have been a considerable lapse of time of which we have norecord. As 
to the length of this unrecorded time, or as to what did or did not take place 
during its lapse, we are left wholly to conjecture, and the assumption that great 
changes had taken place in the organic development of higher from lower specific 
form, is a begging of the question, inconsistent with scientific methods of inquiry. 
With the incoming of the Silurian age, there was the sudden appearance of a 
wonderful variety of somewhat highly developed living organisms, especially of 
the animal series. The fossil remains of more than 10,000 different species of 
animals have been discovered in the rocks of this age, and others are almost con- 
stantly coming to light. Every class of the animal kingdom, except vertebrates, 
was numerously represented in the fauna of that age, while the individuals be- 
longing to many of these species was above computation or even conception. 
Now some of these, as the Trilobites, that came in with the very beginning of 
