610 tuansactions op. section a. 



and the existence of which the kite-flights at Blue Hill have demonstrated. 

 Sometimes there are coincident rhythmical oscillations in the barograph trace. 

 The continuous crests and hollows of the undulations in the clouds extend usually 

 from north to south, or at right angles to their drift, in contrast to the cirrus 

 bands, which move most frequently in the direction of their length. Since the 

 crest of a wave usually lies normal to the wind which produces and propagates it, 

 these observations confirm Von Helmholtz's explanation of the undulations as 

 being the visible crests of atmospheric waves formed between currents of air 

 differing in density and also in velocity or direction. 



Sir Oliver Lodge asked whether the recurrent rapid minor oscillations of 

 brief duration could not be due to a sort of echo or reverberation from the 

 discontinuity layers ; but subsequently he supposed that they might more likely 

 be due to secondary and insignificant vortices accompanying the main depression. 



Sir WiLLiAir Wiixte observed that his interest in wave-motion chiefly centred 

 in water waves, and particularly in deep-sea waves. Observations of ocean waves 

 were of importance to the naval architect, since the behaviour of ships at sea 

 largely depended upon the character of the wave-phenomena, and particularly 

 upon the proportion of the relative periods of approach of waves and the natural 

 periods of oscillation of ships. For many years (under orders from the Admiralty) 

 officers of the Navy made numerous observations of the dimensions and periods 

 of waves which produced oscillations in ships — particularly transverse oscillations 

 of rolling — noting at the same time the actual angles of inclination obtained on 

 each side of the vertical. In this manner the modern theory of rolling (developed 

 chiefly by the late William Fronde and Professor Rankine) was confirmed to an 

 extent surticient for practical purposes. In the case of the ' Challenger Expedition 

 also special orders were given in regard to making observations of wave- 

 phenomena ; but, unfortunately, very little additional mforniation was obtained. 

 There is need for much more extended observation of ocean waves, particularly 

 under the special circumstances when they form a fairly regular series. The 

 phenomena of a 'confused sea' also require much more extensive study. In 

 addition, the behaviour of deep-sea waves during their degradation, when they 

 run into shallow water and approach the shore, deserves careful -study, and has a 

 practical application in regard to the construction of harbours and sea defences of 

 all kinds. 



Up to the present time we have but little definite information available in 

 regard to the generation of waves, and the laws connecting the force and velocity 

 of wiud with the creation of water-waves. The best observations available are 

 those of the late Lieutenant Paris, of the French Navy, and they reflect the 

 greatest credit upon that officer both as to the methods employed and extent of 

 the work done. The analysis of his results, however, shows conclusively that 

 much more extended observation is required. 



Wave-phenomena which accompany the movements of ships through water 

 which otherwise would be still, have received great attention in recent, years in 

 connection with experiments made on models in tanks on the system iutroduced 

 by the late Mr. William Froude, greatly developed in thi.s country by Mr. R. E. 

 Froude, and now extensively employed in all maritime countries as an aid to the 

 design of steamships. This branch of investigation is still in full progress, and 

 it cannot be doubted that wave-phenomena in general may be studied with 

 advantage in such tanks. In most of these establishments the pressure of work 

 in connection with experiments which have a direct bearing upon the designs of 

 new steamships interleres greatly with purely research work. On these grounds 

 it has been advocated for some years past to establish at the National Physical 

 Laboratory an experimental tank, which should be devoted primarily to research 

 work. The Institution of Naval Architects has made various attempts towards 

 the creation of such an establishment, but has failed hitherto. Quite recently — 

 thanks to the generosity of Mr. Al red Yarrow in ottering to meet the capital 

 expenditure required — the question has been brought into a much more hopeful 

 condition. The Institution of Naval Architects is now engaged in obtaining 

 guarantees from shipbuilders and shipowners for an ade(juate fund to meet the 



