546 REPORT — 1886. 



The author then proceeded to show that the extra current at hreaking-circuit 

 ■was much less in motors than in generators, on account of the opposing E.M.F. in 

 motor armatures. He thought that M. Marcel Deprez had in his recent experi- 

 ments taken needless precautions to avoid the effects of extra currents in his motors, 

 and said that he had frequently opened the circuits of Brush generators giving 

 2,000 to 3,000 volts and 10 amperes without in any case doing any harm. 



5. On Electric Induction hetween Wires aoid Wires. 

 By W. H. Pkeece, F.B.S. 



Along the Gray's Inn Road in London the Post Office has a line of iron pipes 

 huried underground carrying many telegraph wires. The United Telephone Com- 

 pany has a line of open wires along the same route over the housetops situated 

 eighty feet from the underground wires. Considerable disturbances were experi- 

 enced on the telephone circuits, and even Morse signals were read which were said 

 to be caused by the continuous and parallel telegraph circuits. 



A very careful series of experiments, extending over some period, proved un- 

 mistakably that it was so, and that the well-known pattering disturbances due to 

 induction are experienced at a much greater distance than was anticipated. 



It became of importance to lind out how far these effects could be detected. 



Experiments conducted on the Newcastle town moor extended the area of the 

 disturbance to a distance of .3,000 feet, while the effects were detected on parallel 

 lines of telegraph between Durham and Darlington at a distance of 10^ miles. But 

 the greatest distance experimented upon was between the east and west coast of the 

 Border, where two lines of wire 40 miles apart were affected, the one by the other, 

 sounds produced at Newcastle on the Jedburgh line being distinctly heard at 

 Gretna on a parallel line, though no wires connected the two places. 



Very careful experiments have shown that these effects are independent of the 

 earth, and are probably inductive effects through the air. 



Distinct conversation has been held by telephone through the air, without any 

 wire, through a distance of one quarter of a mile ; and this distance can probably be 

 much exceeded. 



Effects are not confined to the air, for submarine cables, half a mile apart in the 

 sea, disturb each other. 



6. On a Magnetic Experiment. By W. H. Preecb, F.B.S. 



A broken bit of needle was discovered in a hand by a strongly magnetised and 

 delicately suspended needle when no indications were given by an induction- 

 balance. • 



7. On a new Scale for Tangent Oalvanometer. By W. H. Preece, F.B.S. , 



and H. R. Kempe. 



The instrument is ' slewed ' around, so that the plane of the coil makes an angle 

 of 60° with the mei'idian, instead of coinciding with the meridian, and this point is 

 taken as zero, whence a scale in tangent divisions is drawn, coincident with the old 

 scale of tangent-divisions when the zero and the meridian agree. This renders the 

 instrument far more sensitive to increments of current for high deflexions, while 

 the divisions are still proportional to the current strength. 



8. On Stationary Waves in Flowing Water .^ 

 By Sir William Thomson, LL.D., F.E.S. 



The subject includes the beautiful wave-pattern produced by a steamer under way 

 in smooth water. But the communication to the Section was limited to another 

 interesting and well-known phenomenon, the rippling of the surface of a natural 

 rivulet, or of the water flowing in a mill-stream, or through a conduit of any 



' For the full paper see the Phil, Mag. for October 1886 and the succeeding 

 months. 



