Iasl-arv 1. 1901 J 



K NOWLEDGE 



3 



their experience. The height of the individual waves 

 was often found to vai-y in the projx>rtion of 1 to 2; 

 it was onlv in vei-y favourable conditions that the 

 average height was 0.7 or O.S of the extreme height. 

 In the open ocean a strong wind soon caused waves of 

 as much as 16.4 feet (o metres). 



The distane-e from crest to crest was found often to 

 v<u-v in the proportion of 1 to 3 in two successive waves. 

 In a rising sea the wave length increased more rapidly 

 than the height, a process which was found to continue 

 for several da vs. Thus, to the east of the Cape of Good 

 Hope, during strong west w^nds, which blew with great 

 regularitv for four days, the height of the waves only 

 increased from 19. C9 to 22.97 feet (6-7 metres), whilst 

 the length which w.is but 370.74 feet (113 metres) on the 

 6rst. day had attained 771 feet (235 metres) on the 

 fourtli. This was the greatest daily average length 

 observed, but individual cases occurred in which more 

 than 1312 feet (4^0 metres) separated two succeeding 

 ridges, and an interval of 984 feet (300 metres) was not 

 uncommon. 



Much interest attaches to the determination of the 

 ratio of the length to the height of waves. The minimum 

 observed by Paris, for a train of waves presumably, 

 was 13. but this was among the Kuriles in a cross sea 

 near to land, and with strong currents running. This 

 obsen-ation is therefore not strictly one of ocean waves. 

 In the open ocean with a " moderate breeze " of 16.8 

 knots (geographical miles per hour) the length was about 

 25 times the height, in a gale the ratio is as low as 18, 

 and in a labouring cross sea the ratio does not generally 

 exceed 20. When the wind drops, the waves, of course, 

 flatten out ; when the length has become 40 times the 

 height the condition is that of a " long swell." 



The velocity, according to Paris, is the least variable 

 element. When the breeze had been blowing steadily 

 for some time and the sea was regular, the velocity 

 varied but little from one wave to the next. In fact, 

 he savs, it is a rare thing in the open ocean to see two 

 large waves pass one over anotlier, which would be occur- 

 ring everv moment if there were the smallest difference 

 in their velocities. We shall see later on that another 

 good observer, the Hon. Ralph Abercromby, had quite 

 different experiences on this point. In the open ocean, 

 sufficient depth is pre-supposed ; Paris finds fi-om his 

 daily record that a wind of the same force gives every- 

 where almost the same velocity of wave. He does not 

 consider himself to be " an large," unless he is at a 

 distance from the windward shore of at least twenty 

 leagues ; only then, he says, can the waves attain their 

 full development. 



The following observations were made upon the per- 

 sistence of the swell after the cessation of wind. Having 

 left the strong breezes or gales from the S.W. on 

 October 31st. 1867, for the calm of the tropic of Capri- 

 corn, the ship, now under steam, was accompanied for 

 three days by a swell unruffled by the slightest breath 

 of wind. The S.W. winds had raised regular waves 

 14.77 feet (4.5 metres) high, and 469 feet (143 metres) 

 average length, with a velocity of about 30 knots; 

 sixty hours later, the distance traversed being 350 miles, 

 the velocity of the wave had only diminished 2 per cent., 

 about 0.6 knot, the wave length being 443 feet (135 

 metres). The difference between the lengths of successive 

 waves seems to have remained large. During this period 

 the height of the waves had diminished by one half. 

 Such a swell, if there be a sufficient stretch of open sea, 

 would finally become invisible owing to this flattening 

 out of the wave, for waves are only seen by difference 



of illumination of their front and back, but in this par- 

 ticular case the observer lost sight of the swell long 

 before it was flattened to this extent owing to another 

 cause. During the last (third) day, calm still continuing, 

 it was crossed by a set of waves coming from the east. 

 These were 3.28 feet (1 metre) in height, and 174 feet 

 (53 metres) in wave length, about the same length as 

 those met with afterwards when the ship entered the 

 easterly trade winds. Here the south-westerly swell 

 ceased to bo visible, after having been traced for 150 

 leagues. The smaller swell from the trades was met 

 with 50 leagues from the place where the easterly winds 

 were blowing. 



{To be continued.) 



MONKEY HAND-PRINTS. 



By R. Lydkkkek. 



The ai'rangcmcnt of the fine ridges and grooves on the 

 palmar aspect of the human hand has of late years been 

 studied with great attention — first by Mr. Francis Galton, 

 and subsequently by Mr. Henry, of the Bengal Police — • 

 in order to develop a satisfactory system of identification 

 by means of " finger-prints." To that exceedingly 

 important and interesting subject I shall devote a 

 special article on a future occasion. In the present 

 communication I desire, however, to draw attention to 

 the arrangement of these lines on the hands of monkeys, 

 and their function in both men and monkeys. This 

 study seems to have been first seriously taken up by 

 Dr. D. Hepburn, of Dublin, who communicated to 

 the Dublin Society the results of his investiga- 

 tions, which were duly published in the Trana- 

 acfinns of that Society. The method employed 

 by Dr. Hepburn was to take impressions of the 

 hands of living monkeys on plates of glass coated with 

 printers' ink; but there are many difficulties connected 

 with this operation, and in preparing a series of im- 

 pressions for the Natural History Museum, it occuri'ed 

 to me that I might be able to take them on paper from 

 the hands of monkeys recently deceased. I accordingly 

 communicated with my friend, Mr. F. E. Bcddard, the 

 Prosector to the Zoological Society, a.sking him to be 

 good enough to send me the right hands of some of the 

 monkeys that died in the Society's menagerie. With 

 this request he very kindly complied, and from the 

 specimens which from time to time arrived at the 

 Museum, I was enabled to take, among others, the im- 

 pressions herewith reproduced. Although they are not 

 quite so successful as might be desired, they are yet 

 amply sufficient to show the general plan of arrange- 

 ment of their lines, and the variation to which they are 

 subject in different genera. Enlargements from these 

 same impressions are now exhibited in the British 

 (Natural History) Museum. 



Before proceeding further I must disclaim any inten- 

 tion of poaching on the preserves of the so-called science 

 of " palmistry." This, so far as I can understand its 

 methods, deals exclusively with the folds or creases on 

 the human palm (corresponding with the white lines 

 in the annexed figures), while attention is here concen- 

 trated on the mode of arrangement of the raised ridges 

 and their intervening grooves. It may, however, be men- 

 tioned that the creases in question have, both in man 

 and monkeys, a definite mode of aiTangement, which 

 appears to be due to the position and action of the 

 palmar muscles. What possible connection there can 

 be between such muscular creases and the duration of 

 human life or the vicissitudes of our mortal career may 



