394 Scientific Intelligence. 



acacia, Spanish chestnut and sycamore were active, while the 

 ash, elm, horse chestnut and plane wood were comparatively but 

 slightly active. Exposure to bright sunlight for a short time (5 

 to 10 minutes) served to intensify to a high degree the action of 

 the active parts ; this is true of all wood. This increased action 

 lingers for a considerable time ; red glass, however, prevents this 

 increase of activity. — Proc. Hoy. Soc, lxxiv, 131. 



I. Geology and Mineralogy. 



1. U. S. Geological Survey. — The following publications have 

 recently been issued : 



Latrobe Folio, Penn., No. 110; by M. R. Campbell. The 

 Latrobe district is in the midst of the Pennsylvania coal area and 

 its general geologic structure and economic importance have long 

 been known. There is, however, little discussion of physio- 

 graphic history in the Pennsylvania reports, and it is particularly 

 in this regard that the recent work of Mr. Campbell adds to our 

 knowledge of Western Pennsylvania. 



The Schooley peneplain is recognized in the summit of Chest- 

 nut Ridge. The Harrisburg peneplain, cut in the Schooley plain 

 when the land stood 1200 feet lower than at present, is recognized 

 here as well as in the Monongahela and Susquehanna Valleys. 

 The Harrisburg peneplain is Early Tertiary. A still lower level 

 is described as the Worthington peneplain. The broad valley 

 floor of the Conemaugh, which is such a conspicuous feature 

 between Blairsville and Tunnelton, is found to correspond to sim- 

 ilar features on the Monongahela, Youghioheny and Allegheny 

 rivers, and to date from pre-Quaternary times. This feature is 

 described as the Parker strath. The abandoned channels and ox- 

 bows of these rivers are believed to be the results of ice dams in 

 early Glacial time, and not connected with the draining of Lake 

 Monongahela as suggested by Dr. I. C. White. The streams of 

 this district flowed directly toward the ice front and with the 

 advent of spring the ice melted first at the head of the stream. 

 There was thus opportunity for many ice dams, temporary, or 

 even continuing through several seasons. This hypothesis 

 accounts for many abandoned channels in Western Pennsylvania, 

 which otherwise are inexplicable. 



Zinc and Lead Deposits of Northern Arkansas : by 

 George I. Adams, assisted by A. H. Purdue and E. F. Bur- 

 chard ; with a section on the Determination and Correla- 

 tion of Formations, by E. O. ITlrich, 115 pp., 27 pis., 6 figs., 

 Professional Paper No. 24. In addition to the economic study 

 of the lead and zinc deposits of northern Arkansas, Mr. George 

 I. Adams presents a sketch on the geologic and physiographic 

 history of that region. A number of faults already noticed by 

 the Arkansas geological survey are described and proof given 

 that they are normal faults and not thrust faults, as considered 

 by Branner. A description is given of the brecciated dolomite 



