FACTS AND OBSERVATIONS. xxxvii 



Pal&arcee, while the shales of Point Levis, near Quebec (and the shales only), are crowded with 

 various species of Graptolites, seen for the most part nowhere else. 



These singularities in the geographical distribution of the Mollusca will be explained at the 

 same time with those of the present fauna of Australia, South America, Madagascar, &c. ; but the 

 manner of so doing is still to be wished for. 



The sedimentary strata containing our 9030 organic remains exhibit ample traces of localiza- 

 tion. Upon this subject our space admonishes us to be very brief. The sedimentary strata consist 

 of a few simple forms, about eleven in number, varying in the proportions of their ingredients, in 

 aggregation, and in mass ; but still the limestones, schists, &c. of the most distant countries, and of 

 different parts of the epoch, may be undistinguishable. Many a time, of hand specimens from the 

 Silurian, Triassic, and Jurassic periods, &c., the same may be said. All strata and masses of rock are 

 local, as well as their mineral variations, in breadths of greater or less size. Here a bed is missing, 

 there another, while intercalations, overlaps, and breaks are not unfrequent. Beds being local is 

 not perceived and acknowledged except when they are so small as to permit of being easily traced. 

 In North-east America the Oneida conglomerate, the Onondago-salt group, and the Oriskany sand- 

 stone are striking instances of intercalation of beds only occupying portions of a basin. Doubtless 

 the same occurs in the Old World. 



The Oriskany sandstone is particularly worthy of our study. It is now known to extend to the 

 south of New York, and very far to the north-east of that State (Dana) . It is composed of the 

 unaltered debris of granite, gneiss, and mica, in the form of sand, gravel, and lumps, largely 

 infiltrated with lime. Usually without organic connexion with the limestones below, it indicates 

 the beginning of a new period, and is in fact the base of the Devonian. 



FIRST APPEARANCE. This may be considered, practically, only another term for the date of 

 its creation, liable indeed to mistake in individual cases, which, however, sooner or later meets with 

 correction. While I give my full belief to the sublime utterance of the prophet, " / have made the 

 earth, the man and the creatures that are thereon, by my great power " (Jer. xxvii. 5), the present 

 observations rest wholly on natural-history facts derived from the ' Thesaurus ' and similar 

 sources. 



By far the most important part of a geological formation is its life. Mineral substances, 

 always few in number, are simply ministerial to life. 



The first appearance of individual existences seems to be a normal transaction, not a casual, as 

 it appears to be ; for the great result is beneficial and harmonious. It takes place (we know not 

 how ; no eye saw it) among conditions prearranged for healthy subsistence, and not by transmutation. 



Life started into being, necessarily, in societies both composite and simple ; the composite at 

 once, in the beginning of a stage or at any other time Radiata, Mollusca, Annelida, Articulata, 

 all showing themselves simultaneously, or nearly so, for they subsist on each other. The sporadic 

 method is common to all parts of an epoch ; for there has always been a sowing of solitary forms, 

 together with considerable retention of the old population ; and there was a growth in numbers 

 until a change in conditions came. All this is well known. 



It is a very striking fact that the great majority of the Silurian fauna made their first appearance 

 on the same horizon that is, everywhere on, proximately, the same stage or subdivision of the epoch. 

 The same strata can occasionally be traced with accuracy, and often with little change of constitu- 

 tion, for more than 1000 miles (Potsdam sandstone), but oftener not. In this manner we learn that 

 the conditions were similar in these regions. The recurrent species form the exceptions. 



The lowest traceable place in the succession of strata in which a mollusk is found must be 

 held to be that of its origination or first appearance ; and the fact may be reasoned from with tole- 

 rable safety. Thus we all believe in the various periods at which the Goniatite, Ammonite, Tri- 

 gonia, and Helix first showed themselves. When treating on recurrency, this subject will receive 

 further consideration. 



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