368 



THE ELECTRIC TELEGRAPH. 



become completely charged, and that the quantity of elec- 

 tricity which goes into it, to contribute to the charge, at any 

 moment, after closing the circuit, is represented by the differ- 

 ence between the true insulation and the measured current. 



Time. 



40 min. 



Fig. 169. 



60 min. 



This difference is found experimentally to be inversely pro- 

 portional to the time, or nearly so. 



82. Joints in the Core. After the tests of the single knots 

 of core, these are joined up in lengths of six knots, more or 

 less, to be transferred to the machines in the sheathing 

 works. Joining the core is an operation requiring manual 

 skill, and, above all, scrupulous cleanliness. No joint is ad- 

 mitted into a submarine line unless made by a workman who 

 has had a considerable practice. This is a branch brought 

 to perfection by the Gutta-percha Company. The jointer 

 commences by cutting off the two ends of the core, so that 

 the gutta-percha and copper- wire are " flush ; " he then 



