[12] “On the Photography of Ripples,” by J. H. Vincent, Philosophical Magazine, vol. 43, 1897, p. 411, and also vol. 48, 1899. These photographs of ripples have been reproduced as lantern slides by Messrs. Newton and Co., of Fleet Street, London.
[13] Some smokers can blow these smoke rings from their mouth, and they may sometimes be seen when a gun is fired with black old-fashioned gunpowder, or from engine-funnels.
[14] For details and illustrations of these researches, the reader is referred to papers by Professor H. S. Hele-Shaw, entitled, “Investigation of the Nature of Surface-resistance of Water, and of Stream-line Motion under Experimental Conditions,” Proceedings of the Institution of Naval Architects, July, 1897, and March, 1898. A convenient apparatus for exhibiting these experiments in lectures has been designed by Professor Hele-Shaw, and is manufactured by the Imperial Engineering Company, Pembroke Place, Liverpool.
[15] The French word échelon means a step-ladder-like arrangement; but it is usually applied to an arrangement of rows of objects when each row extends a little beyond its neighbour. Soldiers are said to march in echelon when the ranks of men are so ordered.
[16] See Lord Kelvin on “Ship Waves,” Popular Lectures, vol. iii. p. 482.
[17] More accurately, as the 1·83 power of the speed.
[18] This figure is taken by permission from an article by Mr. R. W. Dana, which appeared in Nature for June 5, 1902, the diagram being borrowed from a paper by Naval Const. D. W. Taylor, U.S., read before the (U.S.) Society of Naval Architects and Marine Engineers (1900).
[19] “Practical Applications of Model Experiments to Merchant Ship Design,” by Mr. Archibald Denny, Engineering Conference, Institution of Civil Engineers, May 25, 1897.
[20] Reproduced here by the kind permission of the editor of Harmsworth’s Magazine.
[21] See Lord Kelvin’s Popular Lectures, vol. iii., “Navigation,” Lecture on “Ship Waves.”