May 25, 18S3.] 



SCIENCE. 



455 



and judicially considered in connection with tlie great 

 mass of stratigrapliical evidence with which it linlvs 

 itself, and of which it furnishes at once the key and 

 clearest exponent. 



Friim this decisive locality, there stretches away 

 north-easterly, 1o Keweenaw Point, a belt of outcrops 

 constantly maintaining the typical character, bedding, 

 and dip of the Keweenaw series. Mr. [Strong mapped 

 no less than fifty-five exposed areas within the coun- 

 ty in which occur the unconformities on the St. 

 Croix {Geol. of Wise, iii.; Atlas, sheet xix.); and 

 no concealed interval of so much as four miles oc- 

 curs along the belt within thirty miles of the deci- 

 sive locality. Tliroughout the whole broad belt to 

 Keweenaw Point, occupying several thousand square 

 miles, all the outcrops, numbered by hundreds, are 

 of the Keweenawan class, and there are none of any 

 other kind. This we conceive to be decisive evidence, 

 notwithstanding some concealment from drift. 



6. To the second class belong the unconformi- 

 ties of Douglas County, in the extreme north-western 

 corner of Wisconsin, and those of the Keweenaw 

 range of Michigan. In the former region, in a dis- 

 tance of twenty-five miles, there are four excellent 

 sections across the junction-line. These have been 

 described in detail, and illustrated by Sweet. On 

 the one side, the Keweenawan beds dip from 35° to 

 50° southward, terminating northward in upturned, 

 worn edges. Approaching these from the opposite 

 direction are horizontal beds, which, at a distance 

 from the contact, are simple sandstones, but, near 

 the junction, become conglomeritic from material 

 manifestly derived from the copper-bearing series. 

 The beds are locally broken and bent upwards near 

 the junction ; but this, in our judgment, does not 

 vitiate the evidence of unconformity at the time of 

 deposition. We maintain that these sections afford 

 strong evidence that the Keweenaw rocks were up- 

 turned before the flat-lying beds abutting against 

 them were formed. 



Upon the discussion of the controverted contact- 

 line along the base of the great escarpment of Kewee- 

 naw Point, I will not here enter, partly because it 

 might be useless without elaborate discussion, and 

 partly because I could scarcely fail to trench upon 

 data that belong to another. The whole region in 

 controversy has recently been re-examined, and 

 sketches carefully prepared, intended to show the 

 exact facts exposed to observation, stripped of the 

 bias of interpretation. Pending their appearance, I 

 need only call attention to the fault-line long since 

 claimed by Foster and Whitney to exist here, — a view 

 in which several subsequent students of the region 

 acquie>ce, among them Irving and myself, with quali- 

 fications. Now, wliile the existence of this fault may 

 be maintained consistently with the view that the 

 flat-lying sand^tones on the ea-^t are the equivalents 

 of the uppermost beds of the tilted series on the west, 

 and also with the view that the eastern sandstones 

 were deposited unconformably against the cliff 

 formed by the upturned beds, the faulting in this 

 case being held to have previously taken place, it is 

 altogether inconsistent with the view that the eastern 

 sandstones pass continuously under the cliff. 



c. Besides the above regions, which present more 

 than a dozen separate localities of actual or approx- 

 imate contact, several other districts atford strong 

 evidence of unconformity, though they do not rise 

 to actual, at least to ocular, demonstration. The 

 more important are found on the upper St. Croix 

 River, on the Snake and Kettle Rivers in Minnesota, 

 and in the vicinity of Lake Agogebic, Michigan. 

 These localities present horizontal quartzose sand- 



stones, regarded as Potsdam, lying near upturned ig- 

 neous and detrital silicate rocks, referred, on the 

 basis of irrefragable evidence, to the Keweenawan 

 series. The relations of these are so close, that all 

 recent investigators who have examined them re- 

 gard them as instances of unconformity between 

 diverse formations, and find no other explanation 

 consonant with the general geology of the region. It 

 was my purpose to present the more significant facts 

 relating to these little-known districts, upon two of 

 which I have made unpublished observations; but 

 space forbids. Let it be observed, however, that in 

 all cases the vipturned beds are distinctly Keweena- 

 wan in type, and are referred to that series on strati- 

 graphical evidence, that, apart from controversy, 

 would be accepted as conclusive, while all the hori- 

 zontal beds, which are exhibited at eight separate 

 localities, are quartzose, and definitely of the type 

 referred to the Potsdam. We hold these to be facts 

 of much significance as parts of the chain of evidence. 

 The wide range of territory represented by these 

 several cases of unconformity adds to their force as 

 evidence of the distingtness of the formations. 



5. The inherent consistency of the view. — The 

 harmony of the foregoing evidences, drawn from 

 diverse sources and from widely separated localities, 

 and the mutual confirmation they lend each other, 

 as well as their accordance with the entire phenomena 

 of the region, are inherent arguments for the correct- 

 ness of the whole. 



0. The dynamic simplicity of the view. — No im- 

 portant orographic movements, beyond those that 

 must be independently assumed to explain the at- 

 titude of the Huronian strata of the region, and such 

 faults as there is independent evidence of, are in- 

 voked. On the other hand, an extraordinary amount 

 of local faulting and disturbance seems necessary to 

 the alternative hypotheses, and this notwithstanding 

 the unmetamorphosed condition of the beds. 



7. The discovery by the United States geologists of 

 a like series in the Grand Canon of the Colorado. — 

 This, while not a direct argument, has an important 

 collateral bearing on the question. By reference to 

 p. 183 of No. 6 of this journal, it will be seen tliat a 

 series remarkably similar to the Keweenawan in its 

 essential characters occupies the same general posi- 

 tion and attitude, lying in inclined, unmetamorphosed 

 beds, uncimformably below the upper Cambrian, and 

 also resting unconformably upon the crystalline ar- 

 chaean series. The observations of Bell show a some- 

 what similar group bordering Hudson's Bay ; but too 

 little is yet known of it to indicate its true horizon. 

 The ultimate acceptance of the Keweenawan group 

 as the representative of an important period in 

 geological history, will, of course, largely depend on 

 the discovery of similar formations elsewhere, or the 

 persistent failure to otherwise fill the gap between 

 the Cambrian and Huronian. 



T. C. Chambeelin. 



Washington, D.C., May 6, 1883. 



LIQUEFACTION, VAPORIZATION, AND 

 THE KINETIC THEORY OF SOLIDS 

 AND LIQUIDS.^ 



This paper discusses at length the two kinds of 

 vibratory motion which the molecule of a solid body 

 may have, rotary and translatory. It is demonstrated 

 that the mean kinetic energy of such an oscillatory 



1 Abstract of a paper presented by H. T. Eddt, Ph.D., 

 University of Cincinnati, to tlie Section of physics and chemis- 

 try of the Ohio raech. inst. , April 26. 



