October 23, 1914] 



SCIENCE 



607 



the deflection of the galvanometer. Hence we 

 would expect that the maximum current den- 

 sity would be set up in the earth's crust, most 

 directly under the sun and parallel with the 

 equator. Consequently the resultant of all of 

 the current filaments set up in the earth's 

 crust would be represented by Fig. 2, in which 

 the currents in the southern hemisphere would 

 be opposite to that in the northern. 



As this current sheet advances westward 

 with the sun, and its magnetic field strikes the 

 various magnetometer needles, there will be the 

 conditions for a westward deflection in the 

 northern hemisphere and an eastward deflec- 

 tion in the southern hemisphere, followed later 

 in the day by a reversed deflection in both 

 cases. 



This experiment on the mud strip was re- 

 peated and the same results obtained with sev- 

 eral kinds of soil to be found here locally. 

 The relation of direction of current and direc- 

 tion of motion of flame was the same for the 

 mud strip as for the iron wire investigated by 

 Tomlinson.^ From what we know of thermo- 

 electric elements, it would seem possible to 

 find conditions where the direction of the cur- 

 rent would be the same as the flame. For 

 instance, in large areas covered by glacial de- 

 posits if one edge of the deposit was heated 

 more than the opposite edge we might possibly 

 find a condition as just stated. Certain it is 

 that oceanic areas would differ from land areas 

 for these thermo-electric earth currents. 



It was interesting to note the effect of pour- 

 ing water on the strip of mud. Fairly large 

 disturbances were produced when one or the 

 other edge of the wet portion was heated. 

 Local showers might thus produce local mag- 

 netic disturbances. 



Blowing air either on one side or the other 

 of a heated section of the strip also produced 

 regular disturbances. Winds in this respect 

 may be a possible cause of magnetic disturb- 

 ances. 



The cooling effect of a cloud passing over 

 the sun or the shadow of the moon sweeping 

 across the earth's surface in an eclipse may be 

 made manifest by setting up these thermo- 

 electric currents which will affect the earth's 



magnetic field. The temperature to which the 

 mud was heated was bearable to the hand. 



Whether these thermo-electric currents 

 actually exist in the earth's crust as due to the 

 heat of the sun's rays, and whether they could 

 be picked out from other earth currents, is a 

 matter to be investigated further, but for the 

 present it does seem worth while to learn 

 more about these thermo-electric currents due 

 to a moving heat source or sink in all sorts 

 of conductors, particularly electrolytic. 



S. E. Williams 



Physical Laboratoky, 

 Oberlin College 



changes of drainage in ohio 



There is probably no state in the union in 

 which the advance of the ice caused more 

 decided and interesting changes in drainage 

 than Ohio. Almost every stream of any impor- 

 tance in the state is now running in a new 

 channel for at least a part of its course, and 

 most of them for practically their entire dis- 

 tance. 



During the progress of the reconnaissance 

 soil survey of Ohio the writer had an oppor- 

 tunity to visit every section of the state and to 

 make some study of the adjustments in drain- 

 age which resulted from the advance of the 

 ice. Some observations and conclusions are 

 believed to be of general interest and may be 

 of value in interpreting changes in drainage 

 elsewhere. 



The most important relates to the probable 

 interglacial rather than preglacial origin of 

 many old valleys in Ohio, but the gravelly 

 nature of all terraces along streams in or 

 issuing from the glaciated section of the state, 

 as contrasted with the silt and clay character 

 of the terraces along nonglacial streams, is 

 also worthy of mention, as this fact often 

 helps to determine the age as well as the 

 direction of flow of some old streams. 



The course of the old Kanawha Eiver was 

 definitely traced many years ago through the 

 hills east of the Scioto in southern Ohio as 

 far north as Waverly, but as to its further 

 course there has been some doubt. The occur- 

 rence of deposits, similar to those in its old 



