472 



SCIENCE 



[N. S. Vol. XXVII. No. 



L. E. Dickson : " On higher congruences and 

 modular invariants." 



Max Mason : " Note on Jacobi's equation in 

 the calculus of variations." 



G. W. Htt.t, : " Subjective geometry." 



G. A. Buss : " A method of deriving Euler's 

 equation by means of an invariant integral." 



C. N. Haskins : " On the second law of the 

 mean." 



Edwakd Kasner : " The contact transforma- 

 tions of mechanics." 



Edwaed Kasneb: "The plane sections of an 

 arbitrary surface." 



G. A. MiLLEB : " Note on the periodic diurnal 

 fractions." 



F. R. Shaepe : " The inner force of a moving 

 electron." 



W. H. Eoevee : " Brilliant points of curves and 

 surfaces." 



Feank Iewin : " Transformations of the ele- 

 ments X, y, y', ■ • ■, yik) that carry a union of 

 such elements over into a union." 



The San Francisco Section met at Stan- 

 ford University also on February 29. The 

 Chicago Section will meet April 17-18. The 

 next regular meeting of the society will be 

 held on April 25. The summer meeting will 

 be held at the University of Illinois, Septem- 

 ber 10-11. F. N. Cole, 



Secretary 



DISCUSSION AND CORRESPONDENCE 



LAFAYETTE DEPOSITS IN LOUISIANA 



To THE Editor of Science : In your current 

 number (February 28, 1908, page 351) Pro- 

 fessor G. D. Harris suggests assigning the 

 Lafayette formation to the Pleistocene, rather 

 than the Pliocene, on the basis of associated 

 fossils brought up in borings from depths of 

 1,500 feet or more. In this connection it 

 is worth while to consider the alternative 

 hypothesis that the beds tapped by the drill 

 in southern Louisiana are redeposited Lafay- 

 ette materials rather than original deposits. 

 It is to be noted as tending to favor the 

 alternative hypothesis that the Lafayette de- 

 posits are made up of residuary products 

 gathered from the interior and laid down 

 along shore (with little admixture of other 

 material) during a period of continental de- 

 pression, the distribution having been effected 



by river currents or wave action, or by both 

 combined; so that it seems improbable that 

 materials of this distinctive type could have 

 been deposited far off-shore, and especially at 

 depths of 2,000 feet or more — for to the depth 

 of the boring noted by Professor Harris must 

 be added the 500 or more feet of subsidence 

 dviring the Lafayette period. It is also to be 

 remembered that among the striking features 

 of the Lafayette formation is its extensive 

 erosion, especially in the Mississippi embay- 

 ment : From a latitude above the mouth of the 

 Missouri to the gulf the formation has been 

 completely removed over an area averaging 

 50 to 75 miles in width, aggregating fully 40,- 

 000 square miles — i. e., about one eighth of 

 the total area of the formation above present 

 tide level. Moreover, it seems certain both 

 from evidence of remnants and from physical 

 considerations that this was the thickest por- 

 tion of the formation; so that in this district 

 something like a fifth of the aggregate volume 

 of the deposits must have been eroded away, 

 largely during the post-Lafayette high-level 

 period when that portion of the continent 

 about the present mouth of the Mississippi 

 stood a thousand feet or more above its present 

 level. During this high-level period the 

 Lafayette materials might well have been re- 

 deposited at what was then a limited depth 

 below the surface of the gulf, with little 

 admixture of foreign matter. Such an asso- 

 ciation would be quite consistent with Pro- 

 fessor Harris's paleontologic evidence; and it 

 has the advantage of consistency both with the 

 physical conditions attending the genesis and 

 partial degradation of the formation, and 

 with the stratigraphic relations found farther 

 in-shore both in the Mississippi Valley and 

 along the middle Atlantic slope. 



W J McGee 



A HANDY substitute FOR THE BLAST BLOWPIPE 

 IN BLOWPIPE ANALYSIS 



It occurred to me that the small rubber bulb 

 which is used to furnish the atomized alcohol 

 for the platinum tip in an ordinary pyrog- 

 raphy outfit, might profitably, where there is 

 no equipment for tapping a compressed air 



