434 MR. T. HEELIS ON THE HEIGHT ETC. OF WAVES 



wave which has not yet attained its maximum^ or by a 

 fresh one in course of formation. If in a gale of wind a 

 large wave be observed approaching the ship and breaking, 

 she will experience it (unless she be so near to the point 

 at which it has broken as to be involved in the broken 

 water) as a comparatively small one ; and on looking to 

 windward, it will be found that after the formation of its 

 foaming crest a wave invariably ceases to dominate over its 

 fellows. 



When the crest of a wave has toppled over, it always 

 seems to sink much more rapidly than it rose ; and I think 

 (but without having been able to verify my conjecture by 

 exact observation) that its altitudes follow the wave-line 

 curve described by Mr. Scott Russell, and that, a line 

 being supposed to be drawn from the point of its formation 

 to that of its extinction, it will be found that its greatest 

 altitude is attained at the point of maximum of such a 

 curve. 



It may also be stated with a considerable degree of con- 

 fidence, although, as before, not yet determined by exact 

 observation, that the length of any one wave forming part 

 of a ridge measured along its base is proportional to the 

 width of the trough; and from what I have observed I 

 should add that its tendency is to be symmetrical on both 

 sides of the point of maximum, although this is often in- 

 terfered with by a variety of causes, such as the cross sea 

 of a cyclone, which produces pyramidal waves. 



The length of a wave seems to depend upon, and bear a 

 definite relation to, the width of the trough between any 

 two successive waves. It is certain, at any rate, that when 

 the waves are low, and the distances between the ridges 

 short, the waves themselves, measured along the lines of 

 their bases, are short also. 



On the 1 8th July 1862, the ship running fast, with the 

 wind and sea right aft, the force of the wind being 7 of 



