252 report — 1859. 



6. By the usual hand-signalling, it was found just possible that legible groups of 

 dots and dashes should be received through 1800 knots at a speed of 20 dots per 

 minute. 



7. The amplitude of oscillation due to various relative speeds can be thrown 

 into a curve which is the same for all lengths ; and since the law of retardation does 

 not depend on the nature or dimensions of the material forming the cable, we can by 

 means of this curve determine from one single observation at any speed, the ampli- 

 tude of oscillation which will be due to any other speed, or in other words, the pos- 

 sible speed of signalling. 



8. The maximum speed of signalling by any given system corresponds, as has been 

 observed, to a certain amplitude of oscillation produced by successive dots. The 

 actual amplitude necessary for each system must be determined by experiment. 



For Morse-signals sent by hand, it can hardly be less than 15 to 20 per cent, of the 

 maximum strength of current due to the battery used. 



Mechanical senders would greatly increase the speed at which signals can be trans- 

 mitted. 



9. A comparison was made between signals sent by alternate reverse currents 

 and those sent by alternate contacts with one pole of the battery and earth. One 

 diagram would serve for both sets of signals, by simply drawing a line parallel to the 

 baseline of the curve at half the height of the maximum, this line being taken as 

 the base- or zero-line for the signals sent by reverse currents, all deflections above this 

 line being called positive, all those below negative. 



10. The use of reverse currents is of advantage in the first signals sent after the 

 line has been completely discharged ; the nature of this advantage may be briefly in- 

 dicated by pointing out that, when no signals are being sent, the spot of light rests 

 on the base-line, which in the common system is at a remote part of the scale from 

 that at which the dots and dashes appear, but in the system of reversals is in the 

 very centre of that portion of the scale. 



The conclusions and experiments were,in the original paper, illustrated by diagrams. 



On some of the Methods adopted for ascertaining the Locality and Nature of 

 Defects in Telegraphic Conductors. By Cromwell F. Varley, Electrician 

 of the Electric and International Telegraph Company, and of the Atlantic 

 Telegraph Company, fyc. 



The author said the plans adopted by him were various : viz. — 

 Case 1. — When a conductor "makes dead earth," i. e. the connexion between the 

 conductor and the earth offers no appreciable resistance, the operation is very simple, 

 and consists solely in ascertaining how much resistance the conductor in question 

 offers to the passage of electric currents. 



Modes of Measuring Resistance. 



He preferred using a standard of resistance and a differential galvanometer. A 

 current from a battery, whose positive pole is connected to the earth, is made to 

 divide and pass round the differential galvanometer in opposite directions. The one 

 half of the clirrent is made to enter the cable whose resistance is to be measured, 

 and the other half to go through the resistance coils to the earth. So much resist- 

 ance is then included in the latter circuit as shall make the divided currents equal in 

 force, when the needle will stand at zero. The number of resistance coils required 

 to make the needle stand at zero indicates the resistance of the conductor ; and if 

 the defect in the insulation he so large as to offer no appreciable resistance at the 

 fault, the amount of resistance will indicate the locality of the fault. 



When no resistance coils are at hand, the following method may be adopted : — 



1st. Having a galvanometer whose resistance is known, and a Daniel's battery, first 

 ascertain that each cell is in good order, and offers no appreciable resistance com- 

 pared with that of the galvanometer. 



2nd. Connect one pole of the battery to the earth, and the other through the gal- 

 vanometer to the cable. 



3rd. Note the deflection. 



