324 REPORT — 1844. 



some of the v.ater which orijjinally served to maintain the level of the fluid 

 or surlace of repose ; tliis hollow is transferred like a hollow wave along the 

 fluid, and there may exist several sucii waves, which I have called residuary 

 negative waves. But these waves do not accompany the primary wave, nor 

 have they the same velocity. See O, fig. 16. 



It is of some importance to note, that these residuary phtenomena of wave- 

 genesis are not companion phcBnomena to the primary wave or positive wave 

 of the first order. They will be separately considered at another time; mean- 

 while it is to be noted that these residuary phaenomena accompany only the 

 genesis of the wave, but do not attend the transmission, as they are rapidly 

 left behind by the great primary solitary wave of the first order. Certain 

 philosophers have fallen into error in their conceptions of these experiments 

 by not sufficiently noting this distinction. 



It is worth notice also, that besides these, many other modes of genesis 

 have been employed ; solids elevated from the bottom of the channel, vessels 

 drawn along the channel, &c.; wherever a considerable addition is made to the 

 height and volume of the liquid at any given point in the channel, a wave of 

 the first order is generated, diftering in no way from the former, except in such 

 particulars as are hereinafter noticed. 



Motion of Transmission. — The crest of the wave is observed to move 

 along a channel which does not vary in dimension, with a velocity sensibly 

 uniform, so that the velocity with which it is transmitted may be determined 

 by simply measuring a given distance along the channel, and observing the 

 number of seconds which may elapse during the transit from one end of the 

 line to the other. This interval of time is sensibly equal for any equal space 

 measured along the path, and hence we determine that the velocity of the 

 wave transmission is sensibly uniform. 



Range of Wave Transmission. — The distance through which a wave of the 

 first order will continue to propagate itself, is so great as to afford considerable 

 facility for accurate observation of its velocity. For accurate observations it is 

 convenient to allow the early part of the range to escape without observation ; 

 for this purpose, that the primary wave, which is to be the subject of observa- 

 tion, may disembarrass itself of such secondary phsenomena as frequently ac- 

 company its genesis, when that genesis cannot be accurately accomplished. 

 A small part of the range is sufficient for this ])urpose, and the remainder is 

 perfectly adapted for purposes of accurate observation, as it continues to 

 travel along its path long after the secondary waves have ceased to exist. 

 The longevity of the wave of the first order, and the facility of observing it, 

 may be judged of from the following experiments, made in 1835-1837. 



Ex. 1. A wave of the first order, only 6 inches high at the crest, had tra- 

 versed a distance of 500 feet, when it was first mtide the subject of observa- 

 tion. After being transmitted along a further distance of 700 feet, another 

 observation was noted, and it was observed still to have a height of 5 inches, 

 and to have travelled with a velocity of 7'55 miles an hour. 



Ex. 2. A wave of the first order, originally 6 inches high, was transmitted 

 through a distance of 3200 feet, with a mean velocity of 7*4' miles an hour, 

 and at the end of this path still maintained a height of 2 inches. 



Ex. 3. A wave 18 inches high, moving at the rate of 15 miles an hour, in 

 a channel 15 feet deep, had still a height of 6 inches, having traversed the 

 same space in 12 minutes. 



Ex. 4. Among small experimental waves of the first order, in small chan- 

 nels, I have selected one, which, whose crest being 1*34' inch high, in a 

 channel 5*10 inches deep, was transmitted through a range of 1360 feet, and 

 still admitted of accurate observation. 



