ON DEEP-SEA SOUNDING. 379 



accidents excepted, this sounding line might out- 

 live the iron plates and frames of the ship. If the 

 sinker gets jammed in a cleft of rock at the bottom, 

 or against the side of a boulder, the wire is inevit- 

 ably lost. Such an accident must obviously be very 

 rare indeed, and there does not seem to be any 

 other kind of accident which is altogether inevitable 

 by care in the use of the instrument. The main care 

 in respect to avoidance of breakage of the wire may 

 be stated in three words beware of kinks. A 

 certain amount of what I may call internal molecu- 

 lar wear and tear will probably occur through the 

 wire bending round the iron guard rod which you 

 see in the afterpart of the instrument, when, in 

 hauling in, the wire does not lead fair aft in the 

 plane of the wheel, as is often the case even with 

 very careful steering of the ship ; but, from all we 

 know of the elastic properties of metals, it seems 

 that thousands of casts might be taken with the 

 same wire before it would be sensibly weakened by 

 internal molecular friction. Practice has altogether 

 confirmed these theoretical anticipations so far as 

 one year of experience can go. My sounding 

 machine has been in regular use in charge of 

 Captains Munro and Hedderwick in the Anchor 

 liners AncJioria and Devonia (Messrs. Hender- 

 son Brothers, Glasgow), for twelve months and 

 seven months respectively, and in neither ship has 

 a fathom of wire been lost hitherto, though 

 soundings have been taken at all hours of day 



