COALING WARSHIPS FROM COLLIERS IN HARBOR. 127 



4. Holding the bucket by the holding rope and paying out the closing 

 rope the bucket empties its load. 



5. Winding in on the inhaul rope and paying out on the outhaul rope 

 the bucket is caused to swing back over the hatch. 



6. Lowering or paying out the bucket lines lowers the bucket until 

 it strikes the coal and the cycle is complete. 



This cycle has been accomplished in an average of twenty-one seconds for 

 an hour, although frequently single-bucket loads have been filled, discharged 

 and returned in fifteen seconds. 



THE MARINE TRANSFER ON THE COLLIERS MARS, VULCAN AND HECTOR. 



The colliers Mars, Vulcan and Hector were built by the Maryland 

 Steel Company under one contract and are similar in all respects. Each 

 ship has ten hatches. Between each pair of hatches are a pair of vertical 

 king posts (Figs. 5 and 6, Plate 36). Each king post carries two steel booms. 

 Between the king posts are four winches, being duplicates of those on the 

 colliers Vestal and Prometheus (Fig. 7, Plate 37). The king posts are short; 

 in fact, too short. When operating the Marine Transfer both booms are 

 fixed. One supports the double swiveled and hinged block (Fig. 9, Plate 37) 

 directly over the center of the hatch. The other is fixed outboard on the 

 side where the coal is to be delivered. The inhaul pulley, which on the 

 Vestal is placed on a boom end, is attached to the rail of the collier. The 

 pendulum rope and counterpoise are omitted. 



The masts and booms on these three colliers are cheaper than on the Vestal 

 and Prometheus, but they are less favorable to the operation of the Marine 

 Transfer. These colliers have wide hatches and a far greater amount of coal 

 can be taken out of them with the clamshell bucket before trimming is 

 necessary than is possible on the Vestal. The operation of the bucket is 

 practically the same on all the colliers. The strain on the rope drawing 

 the bucket outboard on the Mars is greater than the strain on the hoisting 

 rope. This is because the king posts are low and because the point of 

 suspension of the double block is low. It is of the greatest importance in 

 designing ships to carry Marine Transfers that the most careful considera- 

 tion be given to the strains developed. After the strains are computed for 

 a quiescent load a factor of safety of from eight to ten should be employed. 

 The arrangement of masts and booms on the collier Vestal is preferred by 

 the writer to the arrangement on the Mars. 



On the colliers Mars, Vulcan and Hector, fully loaded and with masts and 

 booms as originally provided, the clamshell bucket clears the deck of war- 



