REMARKS CONCERNING SOUNDING WITH THE LE BLANC-MACHINE. 



In addition to the directions given above, the following deserve consideration. A too 

 sudden descent of the weighted scale should be avoided as much as possible, because it might 

 cause a sudden slack between the wire drum and the winding drum. At the same time the 

 movement of the scale should not be interfered with to much as its descent and the succeeding 

 automatic stopping of the machine is the sign that the bottom has been reached, and it is most 

 important that this should be accurately noted. 



Especially in the case of a great depth when the rope is heavily weighted and the 

 weight perhaps increased with thermometers, mistakes are easily made when there is a slight 

 heaving of the ship. 



It is also possible for the machine to be automatically stopped before the bottom is 

 reached, simply on account of the motion of the ship. With the next heave of the ship the 

 rope will recover itself, loosen the brake and start the machine again, unless under the im- 

 pression that the bottom has been reached, the brake has been tightened. In this case there 

 is a danger of the wire breaking, on the scale being lifted up and striking the upper stop 

 unless the attendant loosenes the brake in time. 



If at a greath depth and through the additional weight of waterbottles and thermo- 

 meters, the friction under water is great and the decrease in weight on the lead, reaching the 

 bottom is relatively small, the chances are that in a high sea the apparatus, on reaching the 

 bottom will behave in the same way as mentioned above. It will then be very doubtful whether 

 the bottom has been reached or not. Should the scale remain down, even although the 

 machine starts working again then it is a sure proof that the bottom has been reached and 

 in that case the wire should be hauled in somewhat. 



If the lead is sticking; to the mud the scale wil be lifted. Should the scale fall and 

 remain hanging half way, than this proves that the lead is off the ground and the ballast- 

 weights dropped. Should the tension in the wire be appreciably reduced but the scale remain 

 up, then the lead is off the ground (or out of the mud), but it is not certain whether the 

 weights are dropped. If it requires much exertion to pull the scale down then it is probable 

 that the weights are not slipped. 



The different currents of the upper and lower water layers or the drifting of the ship 

 by side-wind can increase the uncertainty of the ground being reached. In both cases and 

 especially when the ship is rolling, even although the lead has reached the ground, the tension 

 in the wire which is hanging in a bend can suddenly be sufficiently increased to restart the 

 winch and to lift the scale. In this case there is every chance that the wire is allowed to run 

 out under the impression that the ground has not been reached and thus cause the kinking 

 and breaking of the wire. 



From these remarks it will be seen that it is always advisable to use a heavy lead, 

 when sounding in great depths with a heaving ship. The indication that ground is reached will 



