922 



SCIENCE. 



[N. S. Vol. XIX. No. 494. 



that they have been noticeably dragged down 

 along the contact of the individual necks, and 

 that the whole later area of dacitic plugs is 

 down-sunken in respect to the adjacent area. 

 Th\is while much of the faulting was due to 

 the thrust of the intrusion of the necks, much 

 of it accomplished a collapse and down-sinking 

 around the volcanic centers, subsequent upon 

 eruption. 



On account of the extreme irregularity of 

 the volcanic formations, due both to original 

 irregularity and to constantly intervening 

 erosion, it is impossible to project cross-sec- 

 tions underground; but in mines instructive 

 opportunities to study vein faulting in three 

 dimensions are offered. It is there seen that 

 many veins are aifected by intersecting sys- 

 tems of close-set faults, producing sometimes 

 an intricacy almost defying analysis. 



In the Wandering Boy mine, a vein is af- 

 fected by two intersecting systems of faults, 

 each system with a nearly uniform amount 

 and direction of throw. The result of these 

 systems is to produce a zigzag line of equal 

 displacement, diagonal between the directions 

 of the two systems, and the blocks are pro- 

 gressively down-thrown along these lines. The 

 strike of the vein is fortuitously parallel with 

 the trend of equal displacement, and the rela- 

 tion of the dip to the vertical displacement 

 such that one offsets the other, so that drifts 

 perpendicular to each other encounter con- 

 tinually fragments of the vein, which thus ap- 

 pears to occupy in this space a horizontal zone. 



Mr. Cleveland Abbe, Jr., then presented 

 ' The Historic-Economic Signiiicance of the 

 Eall Line of the Atlantic Slope.' The speaker 

 endeavored in a few words to point out the 

 role the Pall Line played in the life of the 

 North American Indians living along its 

 course, showing that it was marked by village 

 sites and may have been used to define tribal 

 boundaries. 



The first European explorers probably never 

 pushed as far inland as the falls of the rivers, 

 and the earliest settlements also were made 

 near the mouths of rivers and located on the 

 coastal plain. Only after these settlements 

 were well established did adventurers and 

 pioneers go out from them to the more remote 



falls. It was also pointed out that the dates 

 of founding settlements at the falls grow 

 later and later from New Jersey to Alabama, 

 presumably due to the increasing distances of 

 those points from the coastal settlements. 



The significance of the falls along the fall 

 line for the industrial development of the 

 bordering regions, and more especially the 

 social and industrial changes which it is bring- 

 ing about in the southeastern states, was also 

 emphasized. This paper will be published in 

 full in the Journal of Geography. 



Alfred H. Brooks, 

 Secretary. 



THE PHILOSOPHICAL SOCIETY OF WASHINGTON. 



The 586th meeting was held May 7, 1904, 

 Vice-President Abbe in the chair. 



Mr. I. E. Fowle, Jr., presented some results 

 of work at the Astrophysical Observatory on 

 ' The Absorption of Water Vapor in the 

 Infra-red Solar Spectrum.' 



The quantitative investigation of the varia- 

 tion, due to atmospheric water vapor, of the 

 transmissibility of our atmosphere to the in- 

 coming solar energy is the primary object of 

 this paper. This transmissibility which de- 

 creases from band to band generally with 

 increasing wave-length, although it increases 

 with increasing wave-lengfh in the separate 

 bands themselves, is well expressed by a modi- 

 fication of Bouguer's formula, e = eja'''^--'''" ; 

 e„ and e are the values of the solar energy of 

 a particular wave-length before and after 

 transmission though our atmosphere, a, the 

 fractional transmission of a unit layer, m, 

 the air mass traversed by the beam and .SSe,, 

 is the aqueous vapor in one air mass as given 

 by Hann's general formula, £„ being the vapor 

 pressure at the earth's surface. Aqueous 

 vapor seems to have no general absorption be- 

 tween 0.7 and 2.0 /J.. Bouguer's formula im- 

 plies the absorption by a given quantity of 

 water in vapor as independent of its density. 



Mr. S. T. Tamura then presented a con- 

 densed mathematical discussion of the prob- 

 lem of ' The Nocturnal Cooling of the Atmos- 

 phere.' The paper does not admit of a brief 

 abstract. Charles K. Wead, 



Secretary. 



