OCTOBEB 7, 1898.] 



SCIENCE. 



465 



occurs very abundantly in pegmatite veins 

 that cut the crystalline schists of the foot- 

 hills of Jefferson county, west of Denver, 

 Colorado. On the Belcher Hill road, near 

 Golden, the tourmaline occurs : (a) in sepa- 

 rate crystals ; (6) in black masses (schorl) 

 in quartz veins ; (c) the same in pegmatite 

 veins ; and (d) in finely disseminated 

 needles replacing biotite and even feldspar 

 and quartz in biotite schists and gneisses at 

 contact with veins of pegmatite and quartz. 

 The beautiful banding and cross-banding 

 produced by this replacement is unusual. 

 The paper was illustrated by specimens and 

 photographs. 



10. Magmatie Differentiation in the Rocks of 

 the Copper- bearinq Series. By Alfred C. 

 Lane, Houghton, Mich. In many of the 

 effusive sheets a difference may be noted 

 between the top and the bottom. At the 

 top the feldspar is oligoclase, at the bottom 

 labradorite. At the top olivine is more 

 conspicuous, at the bottom augite. The 

 oligoclase and olivine were evidently formed 

 before the lava from which the sheet was 

 formed came to rest, at least in part. The 

 augite and labradorite were probably 

 formed later. It is possible that the early 

 formed oligoclase rose to the top, and that 

 the sodiferous magma there formed had not 

 such corrosive action on the olivine as the 

 calcareous magma left below, the latter 

 causing the olivine to be changed to augite. 

 Comparing different flows, we find the same 

 kind of relations that exist between the top 

 and bottom of the same flow. This sug- 

 gests that similar differentiation went on 

 before eruption. 



11. The Volume Relations of Original and 

 ■Secondary Minerals in Rocks. By Professor 

 Charles R. Van Hise, Madison, Wis. 

 This paper discusses the volume relations 

 of secondary minerals as compared with 

 original minerals, and considers this vol- 

 ume change in reference to the depth at 

 which the alteration occurs. 



12. Note on a Method of Stream Capture 

 By Alfred C. Lane, Houghton, Mich, 

 When the divide between two streams is 

 porous, and the valley of one much deeper 

 than that of the other, springs may arise on 

 the side of this deeper valley, which drain 

 the water from the higher valley and thus 

 diminish the erosive capacity of the stream 

 therein, until the higher valley has a stream 

 only in times of rain and is soon eaten into 

 by lateral tributaries of the deeper stream. 

 Various illustrations of this action were 

 given, and it was noted that the streams 

 draining the ice-front during the Glacial 

 period were especially liable to capture be- 

 cause they occupied channels heavily filled 

 with porous gravel and sand. 



13. The Development of the Ohio River. By 

 Professor William G. Tight, Granville, 

 Ohio. A brief review of the literature 

 shows that it has been generally accepted 

 that the Ohio River is a very ancient 

 stream, but recently the work of several 

 geologists in New York and Pennsylvania 

 indicate the Pleistocene origin of the Ohio 

 above New Martinsville. In papers al- 

 ready published by the author the existence 

 of a very ancient erosion basin extending in 

 general from east to west through the cen- 

 tral part of Ohio and Indiana is established 

 by the restoration of many tributary drain- 

 age lines and by deep wells. Further evi- 

 dence is presented in this paper to show 

 that the Ohio in its present location has 

 been established through the appropriation 

 of sections of numerous northwardly and 

 northwestwardly flowing streams by the cut- 

 ting of the ancient cols and the broadening 

 and deepening of the valleys. The ex- 

 planation for these changes is found in the 

 position and action of the ice-sheet in the 

 various sections, thus determining the age 

 of this part of the Ohio valley to be Glacial 

 or Postglacial. 



The theory is proposed that the develop- 

 ment of the Ohio River almost entirely be- 



