266 Scientific Proceedings, Royal Dublin Society. 



dimensions and quantities involved. Every cubic foot of air increases th& 

 lifting force by over 64 lbs. A cubic yard of air exerts a force of buoyancy 

 amounting to 1728 lbs. — a force far in excess of what would be required. The 

 float need possess a volume no greater than that of a sphere 3 feet in 

 diameter. 



There would be many advantages in carrying out the operations in a 

 small boat, preferably a motor-boat or steam-launch. It would be found 

 easier to approximate to a position vertically above the drill ; for, in fact, there 

 may be a considerable component of the force of haulage tending to bring 

 the boat into this position. This horizontal component depends on the 

 distance of the boat from the point vertically over the sounder and upon the 

 depth. If 6 be the angle with the horizontal at which the drill would be seen 

 from the boat, and the lifting wire be supposed to be stretched taut from boat 

 to drill, then / x cos 0, where / is the stress in the wire, gives the horizontal 

 force urging the boat towards the point above the drill. If / is 200 lbs. 

 and = 70°, the force urging the boat towards this point is nearly 70 lbs. 

 Now in the case of a small boat this force would readily move the boat ; but 

 in the case of a ship there would, of course, be no effect. Even at an angle 

 so large as 84° there would be a horizontal component of over 20 lbs., which 

 would at least certainly indicate the proper direction in which the boat should 

 be urged in order to approximate to the vertical position. I think the sound 

 of the bell will also help in finding the vertical position above the drill. 

 I may observe that wind-drift is easily guarded against by the use of a mark 

 dropped at the moment at which the sounder reaches the bottom. This mark 

 must present only a small area above water, and expose a considerable surface 

 below water. A good plan is to let a lightly weighted rope depend from it 

 say to 10 or 12 fathoms. Such a mark will only be moved by currents. 



If the operations are carried out from a small boat provided with power, 

 the following method of drawing the sounder to the surface would probably 

 be found at once safe and expeditious, and one which would avoid many 

 difficulties arising from raising so considerable a weight by the limited 

 mechanical resources of a small vessel. The drill having been lifted from 

 the ooze in the manner described, the lifting wire is taken in on the winding- 

 engine, and the float released. To the lower extremity of the float a block- 

 and-sheave with attached nipper is now fastened. The block and nipper are 

 opened and closed again round the lifting wire. Just above the block a sea 

 anchor is now attached. This sea anchor consists of one or more conical bags 

 of canvas of the usual form. They are tied in series if more than one are 

 required. This anchor must be of sufficient resistance in the water to move 

 but slowly under a considerable horizontal traction. The boat is now backed 



