iii 



Short Tubes or Orifices," on which a paper by Froude was read at the 

 Institution of Civil Engineers, June 15th, 1847. Herein attention 

 was called to the misconception on which was based a then generally- 

 received theory of the flow of gases. This received theory treated 

 elastic fluids as though they were under virtually the same conditions 

 as inelastic fluids. Froude tested by the best means in his power the 

 result of his more correct views by experiment on the flow of air into 

 a more or less complete vacuum. 



Another subject of inquiry in which he put his views on paper 

 (though he did not publish them) was the resistance experienced by a 

 plane moving obliquely through a fluid. Here, as in the previous case, 

 Froude detected and expounded quantitatively the want of correctness 

 of the existing theory, and suggested an improved and much more 

 correct interpretation of the experimental data. The correct theory 

 on the subject is scarcely yet determined, though it is in course of 

 determination by that doctrine of stream lines by the appreciation of 

 which Froude worked so usefully. 



The important bearing of the resistance experienced by an oblique 

 plane upon the consideration of the flight of birds was a constant 

 subject of thought to Froude. He studied the attitudes adopted by 

 birds, especially sea fowl, in soaring, and made many measurements 

 and quantitative calculations on the subject, but never felt satisfied 

 that there might not be cases not to be accounted for by his inter- 

 pretations. 



On his voyage out to the Cape in 1878-9, and at the Cape he 

 pursued his observations, and he wrote long letters on the subject to 

 friends in England. One of his last acts before he was laid up in his 

 short final illness was, though suffering from feverish cold, to measure 

 accurately two albatross obtained for the purpose. 



We will now give an outline of the investigations into the rolling 

 and form of ships, by which Froude obtained a high position among 

 men of science. At the request of his friend Mr. Brunei, his attention 

 had been given to the problems connected with the rolling of ships 

 during the construction of the " Great Eastern " ship, and in 1861 

 he placed before the Institute of Naval Architects a paper embodying 

 the elementary principles by which the rolling of ships is governed. 



In this paper he dealt especially with the leading phenomena of 

 cumulative rolling, and in successive papers at the same Institution, 

 and in Naval Science, he considered the modifying influence of the 

 frictional and other resistances. He also dealt with the cases of 

 abnormal forms of ships. 



As a preliminary to the discussion of the subject of the rolling of 

 ships, Froude had put into mechanical language the essential features 

 of the trochoidal sea wave. He, from the first, verified the principle 

 of the subject by experiments with variously formed models. The 



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