SCIENCE AND PRACTICE. 391 



short circuit for the current to earth from every corner of 

 the apparatus. Therefore, the fewer the pieces used, the 

 fewer the chances are that the " subtle fluid " departs from 

 the way it should go. 



94. Before commencing to pay out a cable, and while the 

 ship is quiet in harbour, careful measurements are made of 

 its insulation, copper resistance, and temperature. 



In commencing to pay out a cable, one end of the shore- 

 cable is put upon the land and carried into the station. The 

 ship pays this out to the end, when it is joined to the middle- 

 cable, or to the deep-sea cable if no middle cable is employed. 

 At this point the officer of the ship takes the bearings care- 

 fully, in his nautical way, and the telegraph engineer takes 

 his bearings in a less scientific and much simpler way. These 

 consist in rough sketches of marked points on the coast. 

 The line which a church makes with a hill, or two hills 

 together, or an inlet with a hill behind should be carefully 

 noted. There are very few coasts which do not present such 

 inequalities as to enable the engineer to find lines between 

 distant objects. Of these lines, two at least should be noted, 

 if possible, making an angle of 90 with each other ; and the 

 objects noticed on the land should be, one as near to the 

 water and the other as far from it as the nature of the coast 

 permits. In the long run, this method is the most valuable, 

 and enables the engineer to return at any time to the 

 exact locality of the joint in case he may want to pick 

 it up. 



From this point begins the most difficult and risky part of 

 submarine telegraphy. The manufacture requires a constant 

 supervision and care ; it has, however, the advantages of 

 terra-firma and any accident may be repaired, because the 

 essential element time, is to be had ; but the laying demands 

 untiring courage and caution, and that, because, when once 

 under way, there is no stopping without danger to the cable, 

 notwithstanding the innumerable casualties which invariably 

 attend a sea voyage. 



95. In his new book* on telegraphy, M. du Moncel says 



* Traite sur le Telegraphie. Paris, 1864. 



