992 



SCIENCE 



[N. S. Vol, XXVII. No. 704 



feet and the displacement diminished as the 

 distance from the fault plane increased. A 

 consideration of the origin of the forces which 

 produced the break shows that they must have 

 been the result of an elastic strain set up in 

 the rocks by the slow movement of the ground 

 at a distance from the fault, and that the 

 strain was of the nature of a shear, and did 

 not consist of compressions and extensions, 

 such as accompany the ordinary bending of 

 beams. The difference in the amount of the 

 displacement at the fault end and at a dis- 

 tance shows that about two thirds of this 

 strain must have existed already at the time 

 of the earlier survey. An analysis of the 

 forces which produced this slow displacement 

 shows that they must have been applied at the 

 under surface of the displaced area, and not 

 at its boundaries, and that they must have 

 been applied in a definite way. The force at 

 the fault plane at the time of the rupture 

 must have been 2,000 pounds to the square 

 inch, and it is probable that the rock in an 

 uninjured condition was too strong to break 

 under this force. It seems probable, there- 

 fore, that the old break along the fault plane 

 had not become completely consolidated, and 

 broke under a smaller force than was neces- 

 sary to break the fresh rock. By analogy with 

 the underground flows which the theory of 

 isostasy has shown exist, it was suggested as 

 a possibility that underground flows might 

 cause dragging forces on the rock above and 

 thus set up the strain which caused the rup- 

 ture along the fault plane. 



Mr. C. K. Wead presented a brief paper on 

 " EiBciency." The word had come down 

 through the medieval Latin with the loose 

 popular'.meanings which it still retains. But 

 in 1854 Rankine seized it, stamped on it a 

 technical meaning and gave it currency where 

 it was greatly needed. The definition he gave, 

 in the course of his studies on the steam 

 engine, was, " The efficiency of a machine is 

 the ratio of the useful worh performed hy it 

 to the whole worh expended on it." This test 

 of efiiciency, which is applied everywhere in 

 mechanical engineering, is coming to be ap- 

 plied in almost every line of human activity, 

 even though the quantities to be compared are 



not always commensurable. For illustration, 

 reference was made to manufacturing, trans- 

 portation, administration, the so-called trusts, 

 philanthropies, war, scientific terminology and 

 so on. 



E. L. Fakis 

 Secretary 



THE GEOLOGICAL SOCIETY OF WASHINGTON 



At the 206th meeting of the society, held 

 on Wednesday evening, May 13, in the Cosmos 

 Club, the following papers were presented: 



Regular Program 

 The Unconformity hetween the Mississippian 

 and Pennsylvanian Rochs in Western Penn- 

 sylvania, and its hearing on Questions of 

 Geologic Correlation: Chas. Butts. 

 In the anthracite basins the Pottsville is 

 1,200 feet thick, the Mauch Chunk, 2,000 and 

 the Pocono, 1,000. On the Allegheny front, 

 in Blair County, the Pottsville is 130 feet 

 thick, the Mauch Chunk, 180, and the Pocono, 

 1,100. The Connoquenessing sandstone near 

 the top is the oldest Pottsville present. In 

 Allegheny Valley, at Kittanning, the section is 

 the same as the last, except that the Mauch 

 Chunk is missing. The top, 400 to 500 feet, 

 of the Pocono is a sandstone, unbroken in the 

 Allegheny front but more or less broken by 

 beds of shale in Allegheny Valley. This is 

 the Burgeon sandstone of the U. S. Geolog- 

 ical Survey, the " Big Injun " sand of the 

 oil-well drillers, and the Logan and Black 

 Hand formations of the Ohio geologists. In 

 Lawrence County the Burgoon is absent, and 

 the lowest Pottsville rests on middle Pocono 

 beds. The Burgoon forms the lower part of 

 the Allegheny Valley walls. The Kittanning 

 region north to Tionesta, where it is eroded 

 off, and the Connoquenessing rests on middle 

 Pocono. At Warren the whole Pocono is 

 eroded and the Pottsville (Olean or Sharon 

 conglomerate) rests on the underlying rocks. 

 These facts indicate an uplift of west and 

 cential Pennsylvania at the close of Mauch 

 Chunk time, with the erosion of all the Mauch 

 Chunk and part, or all, of the Pocono along 

 a strip extending from Newcastle to Warren, 

 the axis of the uplift lying along that line. 



