144 L. Sclnvendler — 0)i Eartli-Currents. [June, 



Such were in short my reasonings when in 1868 I was entrusted by 

 Colonel Robinson, the Director General of Telegraphs, with the introduction 

 of a system of testing the lines in India, and, although the practical objects 

 of that system had nothing whatsoever to do with the solution of the problem, 

 yet the fact that in each test measurements had to be made with positive 

 and negative currents (for the very purpose of eliminating the influence of 

 the natural currents) secured all the data necessary for the quantitative 

 determination of the electromotive force in the line, to which the natural 

 current must be considered proportional, involving only a slight additional 

 calculation without any extra observations. To this end the necessary 

 provisions were made and instructions issued ; and in this manner more than 

 10,000 electromotive forces, producing the natural currents in the lines of 

 India, have been calculated from the tests made between 1868 and 1872, 

 and are now at our disposal ; and although the results of these numerous obser- 

 vations have not as yet been all analyzed, or even compiled, yet in many 

 special cases, and for limited periods, this has been done, and from these we 

 are justified in stating the following as facts : — 



1. All the lines in India are affected by natural currents. 



2. From more than 10,000 observations it has been established that 

 the prevailing flow of these currents between any pair of stations is as of a 

 copper current from the east to the west ; but which is the true direction, 

 or that of maximum intensity, and further whether there is only one such 

 direction, has not been computed as yet. 



3. The strength of the natural current in one and the same line is very 

 variable. 



4. The direction of the natural current in one and the same line, 

 though also variable to a certain extent, is, however, far more constant than 

 its strength, and out of a number of observations there is generally a mark- 

 ed preponderance of currents flowing in the same direction. 



5. The variation in strength and direction of the natural currents in 

 parallel lines of the same length, is far more uniform than might have been 

 expected, considering the many accidental influences to which long overland 

 lines are exposed. 



6. The prevailing direction of the natural current in any line is 

 generallj^ also the direction of the maximum current observed, but this is 

 not the case invariably. 



These general facts point to one probable conclusion, namely, that 

 " earth-currents''' do permanently exist in the lines of India, though they 

 are often, and under certain circumstances, even much, obscured by many 

 other causes, of commensurate magnitude, but more unstable and accidental 

 in character. 



