318 REPORT — 1844. 



owing to the presence of those minute corrugations of the superficial film which 

 form waves of the third order. These corrugations produce on the surface 

 of the water an effect very similar to the effect of those panes of glass which 

 we see corrugated for the purpose of destroying their transparency, and these 

 corrugations at once prevent the eye from distinguishing forms at a consider- 

 able depth, and diminish the perfection of forms reflected in the water. To 

 fly-fishers this appearance is well known as diminishing the facility with which 

 the fish see their captors. This first stage of disturbance has tliis distinguishing 

 circumstance, that the phaenomeua on the surface cease almost simultaneously 

 with the intermission of the distuibing cause, so that a spot which is sheltered 

 from the direct action of the wind remains smooth, the waves of the third 

 order being incapable of travelling spontaneously to any considerable distance, 

 except when under the continued action of the original disturbing force. 

 This condition is the indication of present force, not of that which is past. 

 While it remains it gives that deep blackness to the water which the sailor 

 is accustomed to regard as an index of the presence of wind, and often as the 

 forerunner of more. 



The second condition of wave motion is to be observed when the velocity 

 of the wind acting on the smooth water has increased to two miles an hour. 

 Small waves then begin to rise uniformly over the whole surface of the water; 

 these are waves Of the second order, and cover the water with considerable 

 regulaiity. Capillary waves disappear from the ridges of these waves, but are 

 to be found sheltered in the hollows between them, and on the anterior slopes 

 of these waves. The regularity of the distribution of these secondary waves 

 over the surface is remarkable ; they begin with about an inch of amplitude, and 

 a couple of inches long ; they enlarge as the velocity or duration of the wave 

 increases ; by and by conterminal waves unite ; the ridges increase, and if the 

 wind increase the waves become cusped, and are regular waves of the second 

 order. They continue enlarging their dimensions, and the depth to which 

 they produce the agitation increasing simultaneously with their magnitude, 

 the surface becomes extensively covered with waves of nearly uniform mag- 

 nitude. 



How it is that waves of unequal magnitude should ever be produced may 

 not seem at first sight very obvious, if all parts of the original surface continue 

 equally exposed to an equal wind. But it is to be observed that it rarely 

 occurs that the water is all equally exposed to equal winds. The configura- 

 tion of the land is alone sufficient to cause local inequalities in the strength 

 of the wind and partial variations of direction. By another cause are local 

 inequalities rapidly produced and exaggerated. The configuration of the shores 

 reflects the waves, some in one direction, some in another, and so deranges 

 their uniformity. The transmission of reflected waves over such as are 

 directly generated by the wind, produces new forms and inequalities, which, 

 exposed to the wind, generate new modifications of its force, and of course, 

 in their turn, give I'ise to further deviations from the primitive condition of 

 the fluid. There are on the sea frequently three or four series of coexisting 

 waves, each series having a different direction from the other, and the indivi- 

 dual waves of each series remaining parallel to one another. Thus do the 

 condition, origin, and relations of the waves which cover the surface of the 

 sea after a considerable time, become more complex than at their first genesis. 

 It is not until the waves of the sea encounter a shallow shelving coast, that 

 they present any of the phaenomeua of the wave of the first order (Report of 

 1838). After breaking on the margin of the shoal, they continue to roll along 

 in the shallow Avater towards the beach, and becoming transformed into waves 

 of the first order, finally break on the shore. 



