August 25, 1893.] 



SCIENCE. 



103 



tion of water, the strata or layers of which they are com- 

 posed varying in composition and thickness according to 

 the mineral character of the water and sediments, and the 

 length of time engaged in forming them. They are read- 

 ily distinguished from igneous, or eruptive rocks, by their 

 horizontally stratified apj)earance, and by the occurrence 

 of organic remains, of which some strata are almost whol- 

 ly composed. These remains, which we commonly call 

 fossils, comprise almost every variety of vegetable and 

 animal life of the past, from the lowest fungus to the 

 highest form of animate creation, including also many ex- 

 tinct species of both plants and animals, and which have 

 no living representatives in the types and genera of the 

 present day. 



An examination into the nature and character of these 

 fossil remains, both of vegetables and animals, which 

 have inhabited the globe during the periods of its past 

 history, constitutes the science of palaeontology. 



The sedimentary rocks, which enter so largely into the 

 formation of the earth's surface, oom^Jrise a number of 

 great divisions, distinguished by special and character- 

 istic collections of plants and animals, and these again 

 are further sub-divided, each sub-division having fossils 

 peculiar to itself, and which may easily be recognized by 

 those skilled in paleontology. 



We shall have a clear understanding of the manner in 

 which sedimentary rocks were formed by observing the 

 various natural processes in operation at the present time 

 in modifying the surface of the globe. 



Sediments of various kinds, such as sand and gravel, 

 and clays in solution, are constantly being carried down 

 by streams and rivers and deposited on the bottom of 

 lakes and seas. 



Portions of banks and cliffs on the sea coast are contin- 

 ually breaking away, and, by the action of the water, dis- 

 integrated and sj)read over the bottom. The sediment 

 deposited in this way is generally found to be disposed in 

 horizontally arranged beds or layers, often enclosing- 

 shells and bones, weeds, leaves and branches from trees, 

 and other organic bodies, drifted from the land or carried 

 by the various streams into the sea. In process of time 

 the sediments so deposited become solidified, jjartly by 

 means of the calcareous and silicious matter contained in 

 them, and that derived from the decomposition of the 

 enclosed organic remains, and partly by the pressiire of 

 the superincumbent layers and strata of sedimentary 

 matter. 



In this and similar ways, all the stratified rocks on the 

 surface of the globe have at different jjeriods been built 

 up, enclosing within the various formations the almost 

 innumerable forms of vegetable and animal life peculiar 

 to each successive period. 



The time occupied in the deposition and solidifying of 

 stratified rocks must necessarily have been enormously 

 great. 



It would not be an exaggeration to say that tens of 

 thousands of years would be requisite to bring about the 

 results which are so apparent in all our stratified rock 

 formations. 



The coast line of the Gulf of Mexico, at the mouth of 

 the Mississippi Eiver, has been known for more than three 

 hundred years; and notwithstanding the immense alluvial 

 deposits annually conveyed to the sea by that river and 

 its tributaries for more than three centuries, comjjarative- 

 ly little change has been made by the encroachment of 

 the land upon the sea, and yet there was doubtless a time 

 when the delta of the Mississippi was at St. Louis, nearly 

 eight hundi-ed miles from its present position. 



Another and more forcible illustration may be seen in 

 the various coal fields of the j^resent day. They appear 

 to have consisted, originally, of primeval forests, situated 



in low or marshy ground, which by a sinking of the 

 earth's crust, or some similar natural phenomenon, grad- 

 ually became submerged, and eventually covered with 

 organic sediment of a vegetable kind, and in this condi- 

 tion have been gradually consolidated. In process of 

 time fresh forests appear to have grown up, covering the 

 same area, and in turn have in a like manner disapjjeared 

 beneath the surface. In the coal-bearing strata of Nova 

 Scotia, which have attained a thickness of 14,570 feet, no 

 less than seventeen successive forests have been counted 

 in less than one-third of that depth. Trees four feet in 

 diameter have been found standing erect and almost en- 

 tire, as they originally grew upon the surface. In the 

 coal field of Sydney fifty-nine fossil forests have been 

 distinctly traced, one above another. 



When we take into consideration the time necessary to 

 mature the growth of a forest, the gradual subsidence of 

 the area on which it grew, until the whole was complete- 

 ly submerged, the filling up of the area with decomi^osed 

 organic matter, the formation and growth of a second forest 

 similar to its j)redecessor, and so on until fifty-nine such 

 forests have matured and in turn disappeared, we can form 

 some idea, though very vague at best, of the vast extent 

 of time occupied in fitting up this world as an abode for 

 man. 



Again, when we consider that many stratified rocks lie 

 hundreds and thousands of feet above the level of the 

 sea, that the various strata of which they are composed 

 abound in the fossilized remains of marine shells and ani- 

 mals, that there was a time when these same rocks must 

 have formed the bed of the ocean, and the substratum of 

 numerous other strata ages since abraded from their sur- 

 face, not only will our conceptions of the length of time 

 the earth has existed be greatly enlarged, but rightly 

 considered, we shall also be led to adore the unsearchable 

 wisdom and mighty power by which all these things were 

 made. 



A study of the geology of the Manitou Islands lying in 

 front of North Bay reveals the only exceptional break in 

 all the Laurentian monotony of this district. There, side 

 by side with rocks of the Laurentian sea, we have j)re- 

 sented, in clearly defined outlines, substantial evidences 

 of stratified rock formation belonging to what is common- 

 ly known as the Trenton period, which is only one of the 

 great sub-divisions of the Palssozic age of the earth's his- 

 tory. 



At some time very remote, when this whole region was 

 in the throes of convulsion, when livid streams of molten 

 rock broke forth from beneath, and fire and heat and steam 

 acting in concert aided the work of disintegration, when 

 huge masses of metamorphosed and igneous rock matter 

 were heterogeneously piled into the hills and mountains 

 round about, and when by an unevenly formed subsidence 

 of the earth's crust an immense valley was constituted, 

 now occupied by the waters of Lake Nipissing, amid the 

 wreck of matter and the chaos and confusion that 

 reigned on every hand, a portion of Little JManitou re- 

 mained undisturbed, retaining in an unchanged condi- 

 tion, in its argillaceous and bitumenous shales and cal- 

 careous strata, abundant organic remains of both animal 

 and vegetable life, the internal evidence of its own antiq- 

 uitj'. 



On Great Manitou Island similar evidences exist, but 

 under somewhat changed conditions. There are out- 

 croppings of stratified rock on both the eastern and the 

 western divisions of the island. That on the eastern joart 

 of the island apparently corresj)onds in strike with the 

 exposure on Little Manitou, but appears to have a slight 

 dip to the south or southwest. The whole area, however, 

 is so obscured with drift and bowlders that neither dip 

 nor strike can be determined with any degree of accuracy. 



