170 



SCIENCE. 



[Vol. II., No. 27. 



solid rock, but also in the innumerable chippings 

 that lie scattered about the quarry. 



The rock is magiiesiaii limestone, dresses readily, 

 and, when burnt, supplies excellent lime. Stone from 

 this place is shipped by rail to Winnipeg, where it is 

 used for ordinary and ornamental building-purposes. 

 Many of the fossils being in the form of casts, they 

 frequently interfere "wilh the successful dressing of the 

 stone. About four feet of drift material overlies the 

 rock; but at another quarry lately opened, nearer 

 the river and a short distance farther north, the drift 

 material attains a thickness of twenty feet. The 

 rock is much tbe same, but apparently not so fossil- 

 iferous. 



In the quarry first referred to, the remains of cor- 

 als belonging to the genera Alveolaria, Halysites, and 

 Zaphrentis, are very numerous. Some specimens 

 obtained bear a close resemblance to the genus Favo- 

 sites. Another group of very common fossils are 

 representatives of the genera Orthoceras, Endoceras, 

 Ormoceras, and Cyrtoceras. 



An excellent specimen measuring eight inches in 

 diameter, with three whorls, was found. The specific 

 characters are much obliterated, but in general out- 

 line and appearance it bears a close resemblance to 

 Trocholites ammonius of the Trenton. 



Several imperfect specimens of Trilobites were 

 found. One appears to be a member of the genus 

 Illaeiius. Fragments of Stromatopora are common, 

 showing in all cases distinct lamination, and, in sev- 

 eral, well-defined oscula; while in a few, conical 

 elevations can be observed. The specimens obtained 

 were found among the fragments of rock scattered 

 about the quarry ; but the characters of all are exceed- 

 ingly uniform. The largest obtained measures 7 

 inches across, .^ in depth, and 2 in thickness. The 

 laminae are well marked, numbering four to the line. 

 They present a wave-like appearance, there being 

 three crests in the section under examination. At 

 the summit of each crest a large aperture is observed. 

 Viewing the specimen from the lop, six of these os- 

 cula are seen, all about the same distance apart. 

 As yet, I have discovered no rods or pillars present ; 

 but there is no question regarding the presence of 

 well-marked laminae and oscula. 



I have read carefully the description of the species 

 S. tuberculata, S. pevforata, S. granulata, S. mam- 

 millata, and S. ostiolata, of Nicholson, and S. concen- 

 trica of Goldfuss, and none seem to embrace the 

 species from this quarry. If any reader of Science 

 can suggest the species to which this interesting fos- 

 sil from Selkirk belongs, he will confer a great favor 

 upon the writer. ,J. Hoyes Panton. 



Pre-Bonneville climate. 



In a critical notice of my preliminary report on 

 Lake Bonneville (Science, no. 20), Mr. Davis points 

 out that a certain conclusion as to the history of the 

 basin is not sustained by the phenomena described. 

 Since reading his comment, I have not been able to 

 consult my text; but, if memory serves, his restriction 

 is fully warranted. Still, the conclusion is not of 

 necessity overthrown; for it is based in part on 

 omitted data, the report aiming to present only an 

 outline of the subject. Kow that the matter is up 

 for discussion, it may be well to indicate these. 



The facts set forth are as follows. Above the 

 Bonneville shore-line the topographic forms are those 

 produced by sub-aerial agencies. Below the shore- 

 line the details are of sub-aqueous origin, but the 



larger features are sub-aerial in type. Especially 

 are the great alluvial cones constituting the pedi- 

 ments of some of the mountains continued beneath 

 the old water-margin, their surfaces being lightly 

 etched and embossed by lake agencies. Kvidently 

 these alluvial cones are of pre-Bonneville date; and 

 evidently, too, the goal of drainage — 'the base 

 level of erosion' — -was lower when they were built 

 than during the Bonneville epoch. 



The questioned conclusion is, that the emptiness 

 of the basin during the long pre-Bonneville, alluvial- 

 cone epoch was due to aridity. Mr. Davis acutely 

 perceives, that the adduced phenomena comport 

 equally well with the alternative hypothesis that the 

 pre-Bonneville condition of the basin was one of 

 free drainage to the ocean, the present continuity 

 of the basin's rim having been instituted either at 

 or just before the beginning of the Bonneville ep- 

 och. 



On this hypothesis, the place at which the drainage 

 of the basin was discharged must have acquired 

 the peculiar configuration of a river-channel; and 

 since, as our observations show, alluvial accumulation 

 has not been great in the region during Bonneville 

 and post-Bonneville time, vestiges of this channel 

 should remain. The fact that they have not been 

 found goes far to show that they are not visible; for 

 intelligent search has been made for them, our eyes 

 having been trained for their recognition by the dis- 

 covery of pre-Bonneville channels within the basin. 

 All the low passes of the enclosing rim have been 

 scrutinized. At whatever points, then, earlier drain- 

 age systems have intersected this rim, the channels 

 appear to have been obliterated by the erosive and 

 constructive agencies of land sculpture. 



Again : the principal plain of the Bonneville basin 

 is at heart mountainous. Its surface is level only 

 because the alluvial mountain bases are deeply buried 

 by later deposits. Of the nature of these deposits 

 we know little more than that the uppermost is 

 lacustrine, the Bonneville layer concealing all else. 

 The deposit representing the pre-Bonneville or 

 alluvial-cone epoch must be relatively heavy, and 

 may be assumed to dominate in the determination 

 of the general configuration of the plain. Wilh the 

 basin closed, a certain system of slopes would arise: 

 with the basin open, there would arise a certain 

 other system, definitely related to the point of dis- 

 charge. The actual system of slopes is adjusted to 

 the existing status, — a closed basin, with lacustral 

 sedimentation. 



Assuming that there was at some remote date a 

 channel of outflow, and that the configuration of 

 the plain was adjusted thereto, the period consumed 

 in the obliteration of the one and the remodelling of 

 the other must have been long as compared with the 

 Bonneville epoch. The pre-Bonneville portion of 

 the period — when the basin was closed, hut con- 

 tained no lake — was presumably characterized by 

 a climate similar to the present. 



Tlie aridity of the pre-Bonneville epoch is one of 

 the features associating the Bonneville history with 

 glacial history; for, if it be disproved, the Bonneville 

 flooding no longer demonstrates a climatic episode, 

 and the apparent homology disappears. And the 

 Bonneville oscillations have, of course, no climato- 

 graphic value if they were orographically produced. 

 It is well, therefore, to test thoroughly. every link in 

 the chain of evidence. G. K. Gii.bekt. 



Nevada, July 15, 1883. 



