187^.] L. Schwencller — On Eartli-Oiirrents. 143 



bodies generally. That the great electric convulsions observed from time 

 to time were nothing but the Telegraph signals transmitted from far 

 distant regions to our planet, indicating great physical changes in the uni- 

 verse, long before, if ever, they could be felt by the more rough instruments — 

 light, heat and gravitation — at present the only means by which we recognize 

 our kinship with the outer world. 



" It could be, therefore, easily perceived how important it was to investi- 

 gate such a phenomenon (probably of all the most widely connected) by 

 direct measurements. 



" Now if such electrical disturbances only existed by fits and starts, as 

 was the case during magnetic storms, it would be almost hopeless to 

 attempt a general system of measurement. This was, however, fortunately 

 not the case, since these earth -currents, which during magnetic storms 

 became so violent, seemed to exist permanently, only of very feeble strength, 

 audit was on this subject that he would give some observed facts." 



The general outline of the rest of Mr. Schwendler's communication will 

 be best given in extracts from his paper, which will be printed in full in 

 Part II of the Journal. 



Mr. Schwendler says : 



" The currents observed at all hours of the day and all seasons of the 

 year, in every line throughout India, may be obviously due to many differ- 

 ent causes acting separately or conjointly. These curreats I have desig- 

 nated " natural currents," to indicate the fact of their being in the lines 

 without any direct, or at least intentional, human agency. The causes which 

 may produce natural currents in Telegraph lines are : — 



1. Galvanic action between the earth plates. 



2. Polarization of the earth plates by the signalling currents. 



3. Polarization of badly insulated points in the line. 



4. Atmospheric electricity. 



5. Thermo-electricity. 



6. Inductive capacity. 



7. Voltaic induction. 



8. Earth currents. 



The latter must be considered as produced by an actual difference of 

 potentials between the two points of our planet with which the ends of a 

 Telegraph line are in contact. 



Surely if these " earth-currents" do permanently exist, and further, if 

 they are strong enough to overpower the others, which are evidently of a 

 much more accidental and less permanent nature, then a large number of 

 quantitative observations, judiciously reduced and conveniently compiled, 

 should at least show the tendency of the general law that governs them in 

 strength and direction, leading perhaps finally to tae true explanation of the 

 earth's magnetism and the causes of its variations. 



