IV 



consideration of the great advantages of introducing resistance as a 

 check to rolling, led him to urge the adoption of bilge keels on an 

 enlarged scale. The advantage of such large bilge keels was especially 

 noticeable in the behaviour at sea of the Indian troop ships. 



Contemporaneously with his investigations on rolling, Froude had 

 been pursuing the subject of the resistance of ships, and by experi- 

 ments in models tried first on a small scale and subsequently with 

 models 6 feet and 12 feet long, had satisfied himself of tbe correctness 

 of a definite law which he propounded for the relation between the 

 resistance of a vessel and that of her model, and his law was simply 

 that the resistance varied as the cube of the linear dimension at speeds 

 proportional to the square root of the linear dimension. A correction 

 had to be applied to allow for the increased ardency of surface friction 

 on a short surface like a model as compared with that on the much 

 larger surface of a ship. 



Froude, convinced of the value of model experiments as a measure 

 of the resistance of ships, at the desire of Mr. E. J. Reed, who had 

 examined the experiments and their results, made a proposal to the 

 Admiralty to conduct a series of experiments on models for them. 

 The proposal was accepted, and in the year 1870 the experimental 

 establishment near Froude's house at Chelston Cross, Torquay, was 

 constructed. The main features of this are a covered waterway along 

 which models made of hard paraffin are drawn by steam-power at 

 regulated speed and their resistance automatically recorded. There 

 are machines for shaping the models and appliances for testing the 

 effect of model screw propellers and for making other observations. 



At this time, also, the loss of Her Majesty's ship " Captain" led to 

 the appointment of the Committee on Designs of Ships of War, of 

 which Froude was a member. 



As a work undertaken for this Committee, he tried a variety of ex- 

 periments with models of Her Majesty's ship " Devastation " to 

 exemplify the probable effects of bilge keels in the rolling of that ship, 

 and shortly afterwards, at the request of the Admiralty, he determined 

 by still water rolling experiments with several of Her Majesty's ships 

 the resistance which the forms of their hulls offered to rolling whence 

 might be inferred their probable behaviour at sea. 



Proceeding a step further, Froude devised automatic recording 

 apparatus for continuously registering the rolling movements of a ship 

 at sea, both in relation to the vertical and in relation to a line perpen- 

 dicular to the mean wave surface on which the ship at each moment 

 was placed. From the record given by this instrument the form of 

 the waves in which the ship had been resting could be deduced with 

 accuracy. 



Following urj these experiments on rolling, Froude conducted 

 experiments at sea in Her Majesty's ship " Greyhound," and sub- 



