268 Scientific Proceedings^ Royal Dublin Society. 



A plunger, P, of uniform section, plays from the one cylinder to the 

 cylinder vis-d-vis to it. This plunger is forced to the left when the left 

 ej'liuder is connected through the valve V^ with the receptacle (not shown 

 in the drawing), and tlie right cylinder is in eonneetion with the external 

 water through the valve F^. At the completion of the stroke the valves are 

 suddenly turned through such an angle as will place the left cylinder in 

 connection with the sea and tlie right in connection with the receptacle. The 

 plunger now moves to the right. 



The motion of the plunger is conveyed to tlie drill by means of an 

 attached rack, R, which moves back and forth with the plunger, and engages 

 witli the cogged wheel, W, giving a reciprocating circular motion to it. The 

 drill-tube feeds down through a sleeve, H, so recessed as to engage with 

 projecting ribs upon tlie outer surface of the tube. The drill is in this way 

 rotated one revolution alternately in either direction, and feeds down into 

 the mud under the influence of its weight, which, if necessary, may be 

 augmented by an added weight placed at its upper extremity. The rollers; 

 r, maintain the racks in position against the cogged wheel. 



Referring now to the more detailed vertical longitudinal section and the 

 transverse section through the centre, and also to the section on YY, it will 

 be seen that the cylinders are carried on U-shaped beds continued right 

 across and preserving the alignment of the opposing cylinders ; and that 

 the rack attached to the plunger enters the recess beneath the cylinders, and 

 is engaged with the plunger by a forked projection which embraces a stop 

 upon the plunger. This latter cannot, therefore, be strained laterally by 

 forces reacting through the rack. It is important to notice that the plunger 

 fits loosely in the cylinder, entering it through a leather collar of the form 

 usual in such cases. At its extremity a guide-piece is attached, which 

 permits the water to freely pass it. 



The valves are of stop-cock pattern, and rotate back and forth through 

 about 90" at each reversal of the stroke. A detailed figure shows their construc- 

 tion. It, however, conveys a somewhat exaggerated idea of the dimensions 

 of the ways through the valve. A bore of one millimetre is sufiQcient for the 

 free passage of the water. The water from without enters through a port at 

 the top of the valve. The perforated piece surrounding this port is for the 

 attachment of a cage-like strainer of wire, covered with a fine fabric, so that 

 no coarse particles can enter the cylinder. Connection with the receptacle is 

 made below through a coned coupling. The manner in which the valve is 

 actuated is shown fully in the longitudinal section on XX. (Compare this 

 with the transverse section at centre.) 



The object aimed at is to secure a vapid turnover of the valve through 



