196 



SCIENCE. 



[Vol. II., Ko. 28. 



■wound up periodically by cliance, — we sliall then 

 have an idea parallel to that of an organism living, 

 yet without any vital energy or creative law; but in 

 such a case we should certainly have to assume some 

 antecedent cause, whether we call it 'horologity' or 

 by some other name. Perhaps the term ' evolution ' 

 ■would serve as 'well as any other, were it not that 

 common sense teaches that nothing can be sponta- 

 neously evolved out of that in which it did not 

 previously exist. 



There is one other unsolved problem, in the study 

 of life by the geologist, to which it is still necessary 

 to advert. This is the inability of paleontology to 

 fill up the gaps in the chain of being. In this re- 

 spect, we are constantly taunted with the imperfec- 

 tion of the record; but facts show that this is much 

 more complete than is generally supposed. Over 

 long periods of time and many lines of being, we 

 have a nearly continuous chain; and, if this does not 

 show the tendency desired, the fault is as likely to be 

 in the theory as in the record. On the other hand, 

 the abrupt f>nd simultaneous appearance of new types 

 in many specific and generic forms, and over wide 

 and separate areas at one and the same time, is too 

 often repeated to be accidental. Hence paleontolo- 

 gists, in endeavoring to establish evolution, have been 

 obliged to assume periods of exceptional activity in 

 the introduction of species, alternating with others 

 of stagnation, — a doctrine differing very little from 

 that of special creation as held by the older geologists. 



The attempt has lately been made to account for 

 these breaks by the assumption that the geological 

 record relates only to periods of submergence, and 

 gives no information as to those of elevation. This 

 is manifestly untrue. In so far as marine life is 

 concerned, the periods of submergence are those in 

 which new forms abound for very obvious reasons 

 already hinted. But the periods of new forms of 

 land and fresh-water life are those of elevation, and 

 these have their own records and monuments, often 

 very rich and ample.; as, for example, the swamps of 

 the carboniferous, the transition from the cretaceous 

 subsidence to the Laramie elevation, the tertiary 

 lake-basins of the west, the terraces and raised 

 beaches of the pleistocene. Had I time to refer in 

 detail to the breaks in the continuity of life, which 

 cannot be explained by the imperfection of the rec- 

 ord, I could show at least that nature, in this case, 

 does advance per saltum, — by leaps, rather than by 

 a slow continuous process. Many able reasoners, as 

 LeConte in this country, and Mivart and Collard in 

 England, hold this view. 



Here, as elsewhere, a vast amount of steady con- 

 scientious work is required to enable us to solve the 

 problems of the history of life. But, if so, the more 

 the hope for the patient student and investigator. I 

 know nothing more chilling to research, or unfavor- 

 able to progress, than the promulgation of a dogmatic 

 decision that there is nothing to be learned but a 

 merely fortuitous and uncaused succession, amenable 

 to no law, and only to be covered, in order to hide its 

 shapeless and uncertain proportions, by the mantle 

 of bold and gratuitous hypothesis. 



So soon as we find evidence of continents and 

 oceans, we raise the question, " Have these continents 

 existed from the first in their present position and 

 form, or have the land and water changed places in 

 the course of geological time?" In reality both state- 

 ments are true in a certain limited sense. On the 

 one hand, any geological map whatever suffices to 

 show that the general outline of the existing land 

 began to be formed in the first and oldest crumplings 

 of the crust. On the other hand, the greater part of 

 the surface of the land consists of marine sediments 

 which must have been derived from land that has 

 perished in the process, while all the continental 

 surfaces, except, pejhaps, some high peaks and ridges, 

 have been many times submerged. Both of these 

 apparently contradictory statements are true; and, 

 without assuming both, it is impossible to explain the 

 existing contours and reliefs of the surface. 



In the case of Xorth America, the form of the old 

 nucleus of Laurentlan rock in the north already 

 marks out that of the finished continent, and the 

 successive later formations have been laid upon the 

 edges of this, like the successive loads of earth 

 dumped over an embankment. But in order to give 

 the great thickness of the paleozoic sediments, the 

 land must have been again and again submerged, and 

 for long periods of time. Thus, in one sense, the 

 continents have been fixed; in another, they have 

 been constantly fluctuating. Hall and Dana have 

 well illustrated these points in so far as eastern North 

 America is concerned. Professor Hull of the Geolo- 

 gical survey of Ireland has recently had the boldness 

 to reduce the fluctuations of land and water, as evi- 

 denced in the British Islands, to the form of a series 

 of maps Intended to show the physical geography 

 of each successive period. The attempt is probably 

 premature, and has been met with much adverse 

 criticism; but there can be no doubt that it has an 

 element of truth. When we attempt to calculate 

 what could have been supplied from the old eozolc 

 nucleus by decay and aqueous erosion, and when 

 we take into account the greater local thickness of 

 sediments towards the present sea-basins, we can 

 scarcely avoid the conclusion that extensive areas 

 once occupied by high land are now under the sea. 

 But to ascertain the precise areas and position of these 

 perished lands may now be impossible. 



In point of fact, we are obliged to believe in the 

 contemporaneous existence in all geological periods, 

 except perhaps the very oldest, of three sorts of areas 

 on the surface of the earth: 1. Oceanic areas of deep 

 sea, which must always have occupied the bed of the 

 present ocean, or parts of it; 2. Continental plateaus, 

 sometimes existing as low flats or as higher table- 

 lands, and sometimes submerged ; 3. Areas of plica- 

 tion or folding, more especially along the borders of 

 the oceans, forming elevated lands rarely submerged, 

 and constantly affording the material of sedimentary 

 accumulations. 



Every geologist knows the contention which has 

 been occasioned by the attempts to correlate the 

 earlier paleozoic deposits of the Atlantic margin of 

 North America with those forming at the same time 



