176 



NATURE 



[December 21, 1893 



balanced rudder, from 22° in the Warrior to 37" in the 

 Bellerophon, than from the decrease in length from 380 

 to 300 feet. But it was really for want of experiment 

 and diagram reduced to scale, that the error was com- 

 mitted of exaggerating the element of length. As a fact 



K 



V 



No. I. — Both engines ahead. I35 Revs. 34^ He 



No. 2.— Starboard engine stopped. >April 20, 1881. 

 No. 3. — Starboard engine reversed. JDft. of water, 22-5 F. 

 (Wind nearly ahead at start ; light). 



•7 A. 



Fig. 6.— To show eflfect of Twin Screws. Scale, J inch = 100 feet. 



it is but one element out of many. The Edinburgh, for 

 instance, which is 325 feet long, requires a "diameter" 

 93 yards longer than the Minotaur, which is 400 feet 

 long. 



beginning to be applied to the rudders, so that any helm- 

 angle provided for, could be obtained at any speed. These 

 changes in the elements of mancEuvring powers demanded 

 especial study ; and, most of all, some more complete and 

 accurate method of measurement. Anticipating, I here 

 show, in Fig. 6, what these developments came to in the 

 case of H.M.S. Thunderer, and how little modification 

 the twin-screw can make in the early part of the turn. 



The invention of a satisfactory method of measurement 

 is due to Mr. Philip Watts, late of the Admiralty, who, in 

 the year 1877, applied it to the Thunderer for purposes 

 that had nothing to do with manoeuvring. But the experi- 

 ments showed how very far from circular the path really 

 was, and how misleading the idea of a circular path had 

 been. Collisions, unaccountable before, were now easily 

 accounted for, and a terrible opportunity of bringing the 

 new light to bear was offered when, in 1878, the Bywell 

 Castle ran into and sank the Princess Alice, destroying 

 600 lives. The accident was wholly a question of 

 manoeuvring. Starting, as it was possible to start, with 

 the assumption that the Princess Alice was legally wrong 

 in turning to the left when approaching the Byzuell 

 Castle, disclosing her movement by exhibiting first 

 her red and then her green light in front of the latter 

 ship, the question remained as to what was safe for the 

 Bywell Castle to do .'' She did turn to the right and sink 

 her neighbour. Ought seamen to be instructed that the 

 movement was a right or a wrong one as an answer to 

 the signal received ? The diagram which is reproduced 

 in Fig. 7, was carefully prepared by putting all the facts 

 into line with the best experiments, but it was found im- 



Princess Alice 



Green] \Red 



V 'MO" 



20" • f20" 



Bywell Castle 



Fig. 7. — Scale, J inch = loo feet. 



Fig. 8. — Scale, j inch = loo feet. 



The twin-screw began to make its appearance in the 

 early days of Sir E. Reed's control of our shipbuilding, 

 and he pushed it forward vigorously. Several twin-screw 

 battleships were launched, and others laid down before he 

 left office in 1870. At the same time steam power was 



NO. 1260, VOL. 49] 



possible to bring ideas of the manoeuvring powers of 

 the ships, and the causes of the accident, together into 

 the discussion. The form of the accident was common, 

 and it remains common ; but no teaching yet exists- 

 which might help seamen to avoid it. 



