April 2, [885] 



NA TURE 



503 



ethnography. The authoctonous population of the Phil- 

 ippines, the Negritos, were driven back by two Malay 

 invasions, and are now to be found only in isolated 

 remnants scattered throughout the islands of the archi- 

 pelago. By the first invasion the Negritos were forced 

 from the coast into the interior, where the) remained 

 undisturbed until the second Malay irruption. This 

 drove the first Malay invaders in their turn from the 

 coast, and the descendants of the new comers still occupy 

 the ports and harbours to this day. The Negritos were 

 li stroyed by wars with the first Malays, or com- 

 ibsorbed by marriage with them, that now no 

 them are to be found. The Malays of the first 

 came from Borneo, and are found to-day in the 

 mountain districts of Luzon, under various tribal names, 

 such as the Tingianes, Igorrotos, Guinanes, Apayos, 

 ia< Calnigas, Gaddanes, &c. ; while the 1 ond 

 . now known as Tagals, Pampangos, 

 Ilocanes, Cagayanes, &c, inhabit the coast regions, where 

 they were found by the Spaniards in the third quarter of 

 the sixteenth century. Naturally the various tribes were 

 unable to prevent being influenced by each other, as well 

 .is from without, and to this we must attribute similarities 

 in many respects, and especially in religion, which mark 

 the Malays of the whole archipelago. Allowance too 

 has to be made for the influence of the Chinese, perhaps 

 also of the Japanese, on the tribes living on the coast long 

 the Spanish invasion. The inhabitants of the 

 coast, the Malays of the second invasion, for the most 

 part profess Christianity now, and are well known, but the 

 pagans of the interior, the Borneo Malays, who, accorcl- 

 of. Blumentritt's theory, formed the first invasion, 

 have never been thoroughly investigated, and this circum- 

 stance led Dr. Meyer to spend three months among the 



1 itos. The appendix in which he records his obser- 

 ery full. It discusses the name and extent of 

 the Igorrotos, their territory, and its climate, their build, 

 mode of dressing the hair, and tattooing (which is far more 

 elaborate than that of even the Japanese grooms, and is 

 probably the most complicated in the world), their dress, 

 ornaments, weapons, villages, huts, agriculture, and 

 cattle-breeding, food, and drink, domestic utensils, art, 



: customs at birth, and marriage, and death ; their 

 priests and religion ; head-hunting, war customs, festivals, 

 language, modes of reckoning time and numbers, and 

 their myths and sagas. Finally comes Dr. Virchow's 

 account of an Igorroto skull, and a brief vocabulary. It 

 is this portion of the work which renders it one of scien- 

 tific interest, and prevents it from being a mere amusing 

 account of the modern grand tour. The numerous 

 illustrations which it contains of the tattooing orna- 

 ments, utensils, and the like, add greatly to its value. 

 The Igorrotos are among the disappearing peoples of the 

 earth. They leave the impression of having once pos- 

 sessed a higher culture ; their manufactures now are far 

 below those of even half a century ago, and Dr. Meyer 

 thinks that, like every primitive race brought into direct 

 contact with European civilisation, nothing can save them 

 from ultimate extinction. 



LETTERS TO THE EDITOR 

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Molecular Dynamics 



I THINK there must be some mistake in Prof. Forbes' report 

 of Sir \Vm. Thomson's remarks as quoted in Nature of last 

 week (p. 461) upon the rate of wave-propagation on Mas .veil's 



electro-magnetic theory of light. From the end of the last 

 quotation one would uppose thai Sir Wm. Thomson intended 

 to convey that the rate of wave-propagation that Maxwell's 

 theory asserted to be the same a thai ol light, was the rate of 

 propagation of a variation of a current in a conducting wire. 

 Now Sir Wm. Thomson cannot, I am sure, have intended to 

 convey any such mistaken notion. Maxwell carefully guards 

 against any such mistake by pointing out that conduction 

 of electricity is of the nature of diffusion, and not of a wave- 

 propagation, and so has no definite velocity. What Maxwell 

 has calculated is the rate of propagation of disturbances in 11011- 

 conducti rs, and not in conductors. It is the rate at which the 

 rices, produced in the way considered by Sir Wm. 

 Thomson in the preceding part of this quotation, would be pro- 

 pagated by transverse vibrations. Of course, as Sir Wm. Thom- 

 son asserts, something analogous to a longitudinal vibration may 

 co-exist with these, but Maxwell's theory shows that a medium 

 which would transmit only transverse vibrations would* explain 

 electric and magnetic phenomena. 



Geo. Fras. Fitzgerald 



40, Trinity College, Dublin, March 2; 



[The passage quoted by Mr. Forbes is correctly reported. A 

 more full explanation of this subject will be found in Nichol's 

 "Cyclopaedia," second edition, 1S60, article, "Electricity, 

 velocity of;" reprinted in vol. ii., art. Ixxxi., of my collected 

 mathematical and physical papers. — W. T. ] 



Civilisation and Eyesight 

 Having read with much interest the recent correspondence in 

 Nature on this subject, I am forwarding the results of some 

 observations which I recently made to determine the degree of 

 acuteness of vision possessed by the natives of the islands of 

 Bougainville Straits, in the Solomon Group. 



I examined the powers of vision of twenty-two individuals 

 who were in all cases either young adults or of an age not much 

 beyond thirty. For this purpose 1 employed the square test-dots 

 which are used in examining the sight of recruits for the British 

 army, and I obtained the following results : — Two natives could 

 distinguish the dots clearly at 70 feet, one at 67 feet, two at 65 feet, 

 three at 62 feet, four at 60 feet, two at 55 feet, three at 52 feet, 

 four at 50 feet, and one at 35 feet. The conclusion at which I 

 arrived was that .60 feet represented the average di-tance at 

 which a native could count the dots— a distance rather greater 

 than that at which they should he placed to test the normal 

 powers of vision, viz. 57 feet. 



Of these twenty-two natives I came upon only one whose 

 vision seemed at all defective. In this instance — that of a man 

 about thirty years old — the nature of the cause was sufficiently 

 indicated by the prominence of the eyes and the nipping of the 

 lids, especially when the sight was strained by trying to count 

 the test-dots at a distance. The limit of distance at which this 

 man could count the test-dots was 35 feet. The question which 

 presented itself to my mind in this case was, whether a white 

 man who could count the dots at the same distance — viz. 35 feet 

 — would exhibit to the same degree the external signs of myopia. 

 I might put this query into other words, and ask whether, con- 

 sidering the far-seeing powers of these natives, the peculiai 

 external signs of myopia would not appear with a less degree of 

 this defect than with the white man. 



Natives of these islands are very quick at perceiving distant 

 objects, such as ships at sea. I was often much impressed by 

 their facility in picking out pigeons and opossums, which were 

 almost concealed in the dense foliage of the trees some 60 or 70 

 feet overhead. My attention was not attracted by the unusual 

 size of the pupils; the eyes, however, have a soft, fawn-like 

 appearance with but little expression. In conclusion, I may 

 refer to the circumstance that the interiors of their houses are 

 always kept dark, the door being usually the only aperture 

 admitting light. The object is, I belive, to exclude flies and 

 other insects from their dwellings. Coming in from the direct 

 sunlight, I have often had to wait a minute or two before my 

 eyes became accustomed to the change ; but the natives do not 

 experience this inconvenience. Some hours of the day they 

 commonly spend in their houses, while at night they use no 

 artificial light except the fitful glare of a wood fire. It would 

 seem probable that the influence of the opposite conditions, pre- 

 sented by the bright sunlight and the darkness of their dwellings, 

 would be found in the increased rapidity of the contraction and 

 dilatation of the pupil with the enlargement, perhaps, of the 



