Geology and Natural History. 149 



was measured in heat equivalents by means of an electrical cur- 

 rent which was passed through a suitable conductor in the tube 

 which was exposed to the X-rays. The author attributes the 

 movement of the pressure level to heat, and does not refer to a 

 probable electrification of the air in the tube. — Wied. Ann., lxiii, 

 pp. 160-176. J. t. 



12. Effect of Cathode rays on air. — P. Lenard shows that the 

 cathode rays in air form regions of mist condensation. A jet of 

 steam at a short distance from an aluminum window of a Crookes 

 tube becomes of a bright whiteness and of a cloudy nature. 

 Cathode rays work in this respect far more powerfully than 

 X-rays. A. Paulsen has formed a cathode-ray theory of the 

 Northern lights and he had anticipated a condensation working of 

 the cathode rays. He has also assumed that the rays of the 

 Northern light form clouds. — Wied. Ann., lxiii, 1897, pp. 

 253-260. j. t. 



13. Electric arc between aluminum electrodes. — V. v. Lang, in the 

 course of an investigation of the polarization of electrodes 

 between which the electric arc is formed, finds that a steady cur- 

 rent can be obtained by means of an alternating current which 

 feeds an electric arc between an aluminum terminal and a carbon 

 terminal. The direct current amounts to about six per cent of 

 the alternating current and flows from the positive aluminum to 

 the negative carbon. This action is the reverse of that noted 

 when an alternating current flows in an electrolytic cell in which 

 an aluminum electrode and an electrode of another metal are 

 placed. — Wied. Ann., lxiii, 1897, pp. 191-194. j. t. 



1 4. Stratified discharges of electricity in free air. — Max To epler 

 shows that the phenomena of stratification are not confined to dis- 

 charges in rarified media, but can be produced in atmospheric air 

 at ordinary pressures. The discharges were photographed, thin 

 layers of poorly-conducting substances being interposed between 

 the spark terminals. — Wied. Ann., lxiii, pp. 109-116. j. t. 



II. Geology and Natural History. 



1. On the Geology of Johnson County. Ioioa. — Professor 

 Samuel Calvin has developed some facts of more than ordinary 

 interest in the chapter on Johnson County in the Annual Report 

 of the Iowa Geological Survey (vol. vii, pp. 33-116, 1897). 



The classification of the formations, which is particularly re- 

 markable for the intervals not represented, is as follows, viz: 



Group. System. Series. Staye. 



f Pleistocene f Recent Alluvian 



Cenozoic ■{ or -{ i Loess 



| Quaternary | Glacial < Iowan till 



I { ( Kansan ti 



f Carboniferous \ Pennsylvanian - Des Moines 



( -Mtssissippiau — Kinderhook 

 Paleozoic { I Upper Devonian — State" Quarry 



j Devonian < Middle Devomau f Cedar Valley 



( (Hamilton?) { Wapsipinicon 



t Silurian Niagara Anamosa 



* / Le Claire 



