ON INSTRUMENTS FOR MEASURING THE SPEED OF SHIPS. 211 



the Committee, he most kindly undertook to carry out at the experi- 

 menting tank at his house at Torquay. 



The result of the first portion of those experiments be presented, 

 through this Committee, to the Association at its meeting at Belfast in 

 1874. The second and concluding part he did not live to complete. 



His son, Mr. R. Edmund Fronde, who assisted his father throughout 

 the entire of his first set of experiments, has, however, communicated to 

 the Committee the result of some experiments carried out by Mr. Wm. 

 Froude last year with H.M.S. Iris, upon a pressure log, the form of 

 which was in accordance with the conclusions drawn from the first set of 

 experiments, detailed in the Report of 1874. 



The results are, it is understood, confirmatory of the views held by 

 the late Mr. Froude. 



The Committee deem themselves fortunate to be able to terminate 

 their labours by the presentation of this document as an appendix to this 

 report. They have only to add that having ascertained that the first 

 series of experiments for the Report of 1874 had entailed upon the late 

 Mr. Wm. Froude expenses amounting to 171. Is. 8d., they have refunded 

 that amount to his executors (out of the 501. originally granted to the 

 Committee). 



Appendix. 



To the Secretary of the British Association Committee on Instruments for 

 Measuring the Speed of Ships. 



Chelston Cross, Torquay, 27th July, 1879. 



Dear Sir, — In compliance with your request I proceed to give a 

 description of the character and behaviour of the pressure log used in the 

 M.M. trials of H.M.S. Iris last summer, in so far as it throws light upon 

 the points suggested for further inquiry in ray father's Report to the 

 Committee at the Belfast meeting of the Association in 1874. 



In the Iris two pressure tubes were used which I will call A and B. 

 Both were 1^ inches external diameter. Tube A finished at the outer 

 end in a gunmetal disc 8 inches diameter, and T 2 „ inch thick, turned in 

 a lathe on both faces nicely flat and square to the axis of the tube. The 

 disc extended completely across the tube end, so as to close it. Tube B 

 was simply plugged up, the plug being turned off square and true to the 

 axis, forming a plain flat end to the cylindrical tube. In each tube was 

 fitted a central tube of smaller diameter. A nice clean hole about 

 ^th inch diameter was drilled in the centre of the closed end of each 

 tube, communicating with the central tube, and a similar hole in the side 

 of each tube communicating with the annular chamber round the central 

 tube. In tube A the side hole was distant 2 inches from the outer 

 surface of the disc, in tube B it was distant 3 inches from the outer 

 surface of the closed end. A cross section of each tube is given above. 

 Each of the two chambers in each of the two tubes communicated with 

 a gauge glass, the level of the water surface in which indicated the 

 pressure in the chamber. There were thus four gauge glasses in all, 

 two communicating with the side holes of the two tubes, two with the 

 end holes. 



p2 



