28 LOWEK AND UPPER SILTJEIAN FORMATIONS: 



of infusoria (shelled animalcules), if this fact, which has been 

 announced, could be satisfactorily verified. At the same time, 

 it is admitted that there are strata of immense thickness in 

 this portion of the rock series in some parts of the earth, 

 which exhibit no tokens of that metamorphosis from heat 

 which has been spoken of, and yet are truly Azoic, or destitute 

 of fossils. 



Traces of life first appear in considerable force in the 

 Silurian formation, a series of beds (sandstones, limestones, 

 slates, &c.) on which this name has been conferred, because of 

 its large development in a region of western England, occupied 

 in the time of the Romans by a people called by them Silures. 

 In England this formation is of immense thickness perhaps 

 not less than 30,000 feet implying its deposition in deep 

 seas, and the lapse of a vast space of time between its begin- 

 ning and its close. In the State of New York, in Bohemia, in 

 Scandinavia, in India, and Australia, it has been examined 

 with more or less care, and everywhere found to exhibit cer- 

 tain general characters, and particularly as to its fossil con- 

 tents. And what were the vessels of the mystery of life in 

 the Silurian era, or more particularly its earlier portion, as 

 far as these rocks inform us 1 



One would imagine that, if our present amount of geological 

 knowledge had come to us by some sudden revelation, it 

 would have been with a kind of awe that its first recipients 

 would have waited for this portion of it. But, had they done 

 so, they would quickly have had to admit that nature is 

 simpler than man's wit would make her ; for, behold, a broad 

 answer to the interrogation brings before us little besides the 

 humblest and most unpretending forms of vegetable and 

 animal life ! 



The list includes no land-plants or land-animals. It in- 

 cludes no marine creatures so high as fish. Even of the 

 classes below fish (Invertebrates), it presents generally only 

 examples of humble families. As we grope downward 

 among these early and obscure fields of creation, we find from 

 time to time a few fossils lower than they had before been 

 found in the same situation, but always the tendency is to a 

 limitation of these primitive creatures to very humble forms. 

 In the Skiddaw slates, for example, which are perhaps older 

 than any part of the Silurian formation, we have only fucoids, 

 or impressions of fuci, a tribe of lowly sea-plants, and grapto- 

 lites, a humble polypian family, allied to the sea-pens of our 



