SCIENCE. 



405 



the carboniferous strata which surmounts it ; indeed, ac- 

 cording to the results of the survey, has been removed 

 from the entire uncovered archaean nucleus. Here a re- 

 markable gap occurs ; the next succeeding formation is 

 the carboniferous, and we pass from the primordial at 

 one step to the end of the palaeozoic strata, with the strik- 

 ing omission of the Silurian and Devonian systems. We 

 are then told that the carboniferous limestone overlies 

 conformably this lower rock — a statement hardly credible 

 — that its hard and resistant strata rise in conspicuous 

 relief like an amphitheatric wall around the included and 

 debased archaean area, with a talus of debris composed 

 of its own and Potsdam fragments, piled upon its sides. 

 Beyond the mural escarpments of the carboniferous, a 

 trough-like valley encircles the latter formation like a 

 moat, the bottom of which is formed of the Red Beds, 

 probably Trias or Jura. These consist of marls and clays, 

 sandstone or limestone bands, whose soft material has 

 been easily and largely removed. Beyond this again, and 

 rising from it in steep cliffs, the mechanical basis of the 

 cretaceous is met — the Dakota Sandstone — forming the 

 foot hills which encircle as a final group this geological 

 unit. Beyond again stretches the plains of tertiary 

 strata. 



The history of the Black Hills, as written by this sur- 

 vey, is this : A low archaean area primarily, whose erasion 

 and degradation has furnished the sands, and fragments 

 of which the Potsdam sandstones, conglomerate, and 

 quartzites have been formed, has been finally oveilaid 

 upon submergence with a regular but unconformable sheet 

 of Potsdam rock. The dome thus made has been lifted 

 from the water and lor the long time from the Potsdam 

 to the Lower Carboniferous remained dry land, not even 

 subjected — an extraordinary statement — to considerable 

 denudation. Then the carboniferous sea flowed over all 

 and deposited its even floor of limestone over the Pots- 

 dam, which two, most regularly superimposed, now form 

 the walls of the archaean inclosure, from which they have 

 been remov.ed by erasion. 



The Triassic and Jurassic followed, surmounting the 

 carboniferous with beds of marl and clays, and adding 

 their accumulations to the rising mound of strata. 



Lastly, the cretaceous sealed in the column of deposits 

 so that the ideal dome assumed the form of the adjoined 

 section after upheaval. 



Ideal Cross-Section of the Black Hills. 



1. Archaean Schists. 5. Red Beds. 



. Granite. 6. Jura. 



3. Potsdam. 7. Cretaceous. 



4. Carboniferous. 8. Tertiary. 



Then the uplift occurred which brought these heavy 

 beddings upward in a flat-topped oval displacement, a 

 highland from which, by a process of enormous denuda- 

 tion, the cretaceous and the Jura and Red Beds have been 

 pared away, their slanting beds and monoclinals now sur- 

 rounding the hills. The carboniferous and Potsdam have 

 also disappeared from the large area on the east side of 

 the dome, where the archaean schists are exposed, and in 

 time will retreat further and further, uncovering new por- 

 tions of the azoic terrain. The carboniferous now forms 

 the surface rock of the wide western plateau, and is 

 deeply cut by a net-work of anastomosing canons. A 

 bird's-eye view of the whole presents the aspect of an 

 overturned colossal pastry, with its bottom crust on one 



side badly gnawed away. In this place it would be im- 

 possible to discuss the serious questions which arise in 

 reference to this exposition. Its guarantee is in the field 

 work and observations of its authors, and it certainly pre- 

 sents a geological chapter of extreme interest. 



Prof. Whitfield's important contributions in the palae- 

 ontology form a striking feature in the report. Mr. Jenney 

 reports, after a detailed examination of the mineral re- 

 sources of the country, that " the Black Hills are pre-em- 

 inently a gold-producing region." Mr. Caswell contrib- 

 utes a chapter on the litnology of the Black Hills. 



Very much of general scientific interest is found 

 throughout this handsome volume, and the United States 

 Government have, in its publication, added one more 

 honor to its deserved eminence amongst nations re-organ- 

 izing science, and added one more debt to the increasing 

 sum due to it from all scientific students. 



L. P. Gratacap. 



Washington, 1880. 



THE GREAT PRIMORDIAL FORCE.* 

 By Henry Raymond Rogers, M. D., Dunkirk, N. Y. 



The law of " Conservation of Force " having received 

 the full and unqualified endorsement of all true scientists, 

 >s to-day the basis of all physical philosophy and the 

 key to the explanation of all physical phenomena. No 

 view of force can henceforth be accepted which is incom- 

 patible with it. 



It may be said to be the product of the last half cen- 

 tury, its origin being obscure and uncertain. Its earlier 

 conceptions evinced but little promise of the grand 

 future that awaited it, and its advancement, like that ot 

 all fundamental truths, has been exceedingly slow. It 

 must be confessed that to-day, even, our knowledge of its 

 provisions is but rudimentary. In the way of applying 

 it to the explanation of the mysteries ot nature's varied 

 phenomena but little has yet been done. We are con- 

 fident that whenever this immutable law shall be properly 

 applied, a new era will have dawned upon physical 

 science. 



Another fundamental principle of recent discovery has 

 been developed pari passu with that mentioned, and in 

 importance is only secondary to it, viz : — the " Unity of 

 Force,"— the correlation of all the forces. It has been 

 demonstrated that all forms of force are resolvable into 

 one another, it is therefore manifest that whatever name, 

 or designation, we may give to these varied forms, but 

 one essence pervades and animates them all. Instead of 

 many independent forces, set forth in an irrational, con- 

 tradictory, and mostly complicated philosophy, actually 

 there exists One Great Primordial force ; simple in its 

 character, competent to explain all physical phenomena, 

 and in harmony with the nature of things. It is the 

 force that rules the universe of matter, — innumerable 

 star-suns and minutest atoms alike ; and, for its realm, it 

 has the vast bewildering space and all the cosmical 

 bodies which occupy its depths. 



This force is real and substantial. " Conservation of 

 force proves as certainly as it proves anything, that all 

 force is substantial. Nothing can be conserved, or pre- 

 served, unless it is something that exists, and it seems to 

 be an axiomatic truth that nothing can exist unless it be 

 a substance of some kind. If force in one form is con- 

 vertible into force of another form, then all force in 

 whatever form it may be exerted is substance, since it is 

 impossible to conceive ot the conversion of one thing into 

 another thing, and neither thing be anything substantial. 

 Our inability to take cognizance of the constituents, or 

 corpuscles of a force, is no valid reason to a thoughtful 



* Read before the A. A. A. S., Cincinnati, 1881. 



