238 



SCIENCE. 



[N. S. Vol. V. No. 110. 



this series contains the Dermaptera and Coleop- 

 tera, in which the hind wings are transversely 

 folded, and the Plecoptera, Platyptera and Or- 

 thoptera, in which the hind wings are longitudi- 

 nally folded beneath the primaries. The second 

 series is that in which the prothorax is fairly 

 well developed, but is quite closely attached at 

 its base to the other segments, and is not freely 

 movable, as in the case of the first series. In 

 this branch, which was terrestrial from the 

 start, are included the Isoptera, Mallophaga, 

 Corrodentia and Neuroptera. The third series 

 had the prothorax reduced in size from the be- 

 ginning, and always united to the other thoracic 

 segments, the general tendency being towards 

 a complete loss of function of all save the legs 

 in this part. All the members of this series 

 are from an aquatic form, and they include the 

 Odonata, Ephemerida, Trichoptera, Lepidop- 

 tera, Mecoptera, Siphonaptera, Diptera and 

 Hymenoptera. From the Neuroptera, as gen- 

 erally understood, he separates the Sialidae, 

 which he makes, with its relatives, an order 

 under the term Platyptera. 



This paper was actively discussed by Messrs. 

 Banks, Gill and Ashmead, who criticised de- 

 tails rather than the general ideas expressed. 



Dr. A. D. Hopkins, a corresponding member 

 of the Society, presented some notes on Scoly- 

 tidse, with descriptions of four new species, viz. : 

 Pityophthorus frontalis, a species which infests 

 dead oak twigs ; P. fagi, which infests peach 

 twigs; Thysanoes querciperda, infesting oak, and 

 T. obscurus, reared from hickory twigs. 



L. O. Howard, 



Secretary. 



GEOLOGICAL SOCIETY OF WASHINGTON. 



At the 56th meeting of this Society, held in 

 Washington, D. C, January 13, 1897, com- 

 munications were presesented as follows : 



The Measurement of Faults : J. E. Spueb, 

 U. S. Geological Survey. Faults are simple 

 movements in the rocks of the earth's crust 

 along fracture planes, and, since these planes 

 may stand in any attitude, there is no rule by 

 which the nature of a fault may be judged be- 

 forehand. The existence of a fault can be de- 

 termined by the evidences of friction along the 

 plane of motion, such as fault breccia, polished 



and striated rock faces and so on ; the amount 

 of movement, however, can be completely as- 

 certained only by the aid of independent and 

 accidental phenomena. In homogenous rock 

 masses the amount of movement cannot be 

 ascertained ; in heterogeneous rocks it may ordi- 

 narily be ascertained with greater or less ac- 

 curacy, and the variations in rock masses must 

 be used as criteria. The commonest variations 

 which are constant enough to be reliable as 

 data are sedimentary beds, and hence it is easy 

 to fall into the error of considering faults simply 

 as dislocations of strata. In careful geological 

 work, however, any available criterion must be 

 regarded as of as much value as any other ; in 

 mining geology the most valuable are, besides 

 sedimentary beds, igneous bodies (such as 

 dikes), bodies of ore, striae on the fault plane, 

 showing direction of movement, and the com- 

 position of the fault breccia, which may show 

 in some degree, the amount of movement. 



In seeking to measure a fault it is necessary 

 to have clearly in mind some of the principal 

 functions of fault movement. Among these 

 functions certain which are of greatest impor- 

 tance are adopted and defined. These are : 

 Total displacement, lateral separation, perpendicu- 

 lar separation, throw, vertical separation and offset. 

 The number may be increased indefinitely, yet 

 ordinarily this is undesirable. 



Glaciation of Paget Sound Region: Bailby Wil- 

 lis. During the past season the drift deposits 

 about the southeastern edge of Puget Sound 

 have been studied in some detail. They are 

 found to consist of several beds of till, separated 

 by stratified deposits of clay, sand and coarse 

 gravel, together with widely distributed lignite 

 beds. The character and extent of the glacia- 

 tion of the Puget Sound region are indicated in 

 these deposits, and it is found that the principal 

 flow of the ice was rather from the north than 

 from the mountains on the southeast. Two 

 problems are presented by the phenomena i 

 (1) the sequence of glacial advance and retreat, 

 and the extent and duration of climatic changes 

 indicated by the presence of lignites ; (2) the 

 bearing of the peculiar conditions of glacial de- 

 velopment upon the physiography of the sound. 

 Either the deeper valleys of the sound have 

 been eroded during a period of high level from 



