36 



NATURE 



[May 12, 1898 



Having thus found a way of representing stream lines 

 by colour bands, various electrical problem?, and problems 

 connected with the flow of heat, can be solved in cases 



Fig. 10. — Section of screw shaft strat (: 



where it would be impossible to obtain direct mathemat- 

 ical solutions. It is sufficient for the present purpose to 

 give one or two illustrations of the application of tlie 

 method to problems of interest connected with the flow 



Fig. II. — Sinuous motion in gradu.-illj- enlarging and 

 (thick sheet). 



Fig. 12. — Colour bands in gradually enlarging and contracting channel 

 (thin sheet). 



of water. Thus, Figs. 9 and 10 illustrate the flow re- 

 spectively in the case of broad and narrow stream bands 

 round a section of the twin screw strut of one of Her 

 Majesty's cruisers. This might of course be the section 

 of a ship-shaped vessel moving through the water, and as 



NO. 1489, VOL. 58] 



is well known the width apart of the different stream 

 lines would indicate the pressure and velocity in the fluid 

 at every point. Thus stream lines can be obtained in 

 such a case representing a process which for this form 

 of section it would be practically impossible to do by any 

 mathematical process. Figs. 11 and 12 illustrate the 

 flow of water through a passage which gradually enlarges 

 and then contracts. The former ca§e represents the flow 

 under ordinary conditions with the thick sheet of water ; 

 the latter case, Fig. 12, being the flow of the colour bands 

 moving in a very thin sheet of water. One more case 

 may be given even more remarkable than any of the 

 foregoing, that is the case of a sudden enlargement of the 

 section of a pipe. Fig. 13 represents the ordinary case 

 of a thick sheet of water in which the eddies and whirls 

 plainly indicate why it is that such a large loss of energy 

 occurs under these conditions in a pipe ; while Fig. 14 

 shows how a perfectly incompressible and frictionless 

 fluid would flow under the same conditions. This is, 

 however, actually what occurs with a thin sheet of water 

 with suitably arranged colour bands. 



KiG. 13. — Sudden enlargement (thick sheet.) 



(thin sheet). 



It may be well to remark that all the figures in this 

 article are actual reproductions of photographs of flowing 

 water, which have all been projected on a screen by 

 means of a lantern at the two recent meetings of the 

 Institution of Naval Architects. H. S. Hele-Shaw. 



FORTHCOMING MEETING OF THE 

 BRITISH ASSOCIATION. 



THE preparations in Bristol for the meeting of the 

 British Association on September 7 proceed apace, 

 and local interest is now thoroughly aroused. The 

 material for the handbook is nearly all in the hands of 

 the editor (Dr. Bertram Rogers), and most of it in type. 

 Among the contributors we note the names of E. J. 

 Lowe, F.R.S. (Meteorology), C. Lloyd Morgan (Geology 

 and Prehistoric Archaeology), A. I3ulleid (Glastonbury 

 Lake Village), A. T. Martin (Roman Archaeology), 

 J. Latimer (History), J. R. Bramble (Architecture), Dr. 

 D. S. Davies (Sanitation), J. W. White (Botany) J. M. 



