264 Scientific Proceedings^ Rot/al Dublin Society. 



There appears to be a critical velocity wheu the mud is water-covered, 

 beyond which the ooze rapidly loses its hold upon the drill, and lets it run 

 away. When this is once reached, a lesser force serves to produce the rapid 

 rotation, as No. 10 seems to show, and again No. 14, made shortly after. 

 But it is to be remembered that the mud flooring the ocean, left for ages 

 undisturbed, is probably in a much more compacted condition ; if, indeed, it 

 is not in a state approaching that of chalk at a little depth from the surface. 



It might be found desirable to give the drill a rotary motion in one 

 direction only. This can readily be accomplished by the addition of two free 

 wheels on the driving-collar, an idle wheel connecting both by bevelled 

 gearing, and both free wheels driving the collar, or running free, when 

 moving rotationally in the same direction. Suppose one rack gears on the 

 upper free wheel and the other on the lower. Then when the upper rack 

 moves from right to left, the free wheel geared with it directly drives the 

 collar, and when it moves from left to right this free wheel runs free ; but as 

 it transmits its motion to the lower wheel, turning it in the contrary direction, 

 the latter now drives the collar. The second engine, geared on the lower 

 wheel, acts in the same manner. This mechanism gives an intermittent 

 rotation in the one direction. A double set of free wheels, each set 

 separately driven with a difference of phase of one-half a stroke, will give a 

 practically continuous uniform motion in one direction. Of course any 

 desired arrangement of phase may be arranged for and maintained with 

 certainty by the coupling of the valves. 



The problem of rock-drilling calls for a fast and light stroke of less 

 power, as well as special arrangements for grasping and cutting off the 

 drilled-out core. I shall not here consider these conditions otherwise than to 

 observe that I believe an engine of the type already described is best for the 

 purpose, but of lesser plunger-area and more rapid stroke. 



Finally, it is desirable to describe certain modifications of the customary 

 methods of raising sounding-machines in deep water. It is impossible to 

 operate always in still water. The effect of a swell when loosening the 

 drill might result in putting serious stresses upon the lifting wire — stresses 

 which no convenient arrangement of absorption springs could guard against. 

 To avoid this danger the stress is first applied through the arrangement 

 shown in figure 1. A pulley-block is let run down the wire, and when it has 

 gone down a few fathoms a nipper makes it fast. Beneath the sheave of the 

 pulley a rope leads to a float, the other end being hauled from the ship. 

 Now, in this case one-half the actual lifting force is applied from the ship, 

 und the effect of this force is to partly submerge the float. The safe limit 

 of stress is conditioned entirely by the dimensions of the float, and may be 



