484 



SUBMARINE CABLE LAYING AND EEPAIRING. 



which the blades can be moved up or down. The blades are 

 connected respectively to the cable and condenser. The 

 insulated handle is raised to " charge," which moves the con- 

 tact blades downwards, making rubbing contact with the two 

 outside blocks c and d connected to the slides. For mixing, the 

 handle is pushed down, when the contact blades are raised and 

 touch the middle block e, thus connecting the cable and con- 

 denser. A small key is provided for putting the galvanometer 

 in circuit. Fig. 268 shows the key as connected up for taking 

 the test. 



Gott's Capacity Test. — This test, suitable for the measure- 

 ment of capacity of long cables, and due to Mr. John Grotfc, was 

 described in the Journal of the Society of Telegraph Engineers 



F V 



a Slides b 10,000 



Fig. 269.— Gott's Capacity Test. 



1881 (Vol. X., p. 278). It is practically the same as Sir William 

 Thomson's second method, described by him ia 1872 (Vol. I. of 

 the Journal of the same Society), in a Paper " On the Measure 

 ment of Electrostatic Capacity," but was independently devised 

 by Mr. Gott and published as above after having proved it 

 with success on a number of laid cables by tests afloat 

 and ashore. He pointed out that the method gave identical 

 results with that of Sir William Thomson, and was sometimes 

 more convenient, as a carefully insulated battery was not re- 

 quired. Sir William Thomson said of the test that it was 

 " applicable, notwithstanding earth currents in moderation, to 

 measure the capacity of a submerged cable of 2,000 or 3,000 

 miles with only a single microfarad as standard for capacity 

 and a battery of not more than 100 cells to charge it." 



