April 9, 1885] 



AATURE 



545 



'I hroughout this paper the density of the water is given as 

 reduced to 15 '56 C. (60° F.). It is specific gravity at I5°"56 

 pure water at 4° C. as unity. 



The water-sampling stations and the principal contour lines of 

 depth are shown in the chart of the Firth of Forth (Fig. 1). 



THE PEARL FISHERIES OF TAHITI 



A 



■ V issue of the Joiirnu OH id contains a lengthy 

 report by M. Bouchon-Brandely, Secretary of the College 

 . il I , who was sent by the Ministry of Marine and the 



11 a mission to Tahiti to study questions relating to 

 Iture there. The principal product of what M. 

 i ■! . "the summer isles of Eden " fresh in his mind, 



et si poclitjue colonie de Taiti" is mother-of- 

 pearl. All its trade is due solely to this article, which for a 

 century has regularly attracted vessels to the islands which com- 

 pose the archipelagoes of Tuamotu, Gambier, and Tubuai. 

 The 111 ither of-pearl which is employed in industry, and espe- 

 cially in French industry, is furnished by various kinds of shells, 

 the most estimated, variegated, and beautiful of which are those 

 of the pearl oyster. There are two kinds of pearl oysters — 

 one, known under the name of pintadine (Mdeagrina margaret- 

 ifera), is found in China, India, the Red Sea, the Comoro 

 islands, North-Eastern Australia, the Gulf of Mexico, and 



in the Tuamotu and Gambier archipelagoes ; the 

 other, more commonly called the pearl oyster {Meleagrina radi- 

 ala), comes from India, the China seas, the Antilles, the Red 

 Sea, and Northern Australia. The shell of the former is harder, 

 more tinted, more transparent, and reaches greater dimensions 

 than the latter. Some have been found which have measured 



imetres in diameter and weighed more than ten kilo- 



grammes, while the Meleagrina radiala rarely exceeds ten centi- 



the most, and never weighs as much as 150 grammes. 



Both varieties supply pearls, tho^e of one kind being at one 



favoured, at another time those of the other. This 



on fashion ; but, on the whole, those found in the great 



.ire more beautiful, and the colour more transparent, 



of its congener. The amount of the trade from Tahiti 

 be stated with accuracy, as there is much clan- 

 destine traffic, but M. Brandely puts it down approximately at 

 300,000 francs, England, Germany, and the United States being 

 the chief markets for the fine pearls. The great pintadine is 

 found in great abundance in the Tuamotu and Gambier islands. 

 The situation there is very favourable to them ; in the clear and 

 limpid waters of the lagoons they have full freedom for deve- 

 lopment, and are undisturbed by storms. Mother-of-pearl is 

 found in almost every one of the eighty islands which form the 

 archipelagoes Tuamotu and Gambier. These belong to France, 

 having been annexed at the same time as Tahiti and Moorea, 

 and have a population of about 5000 people, all belonging to 

 i race. M. Brandely gives an interesting description 

 of these little-known i-lands and people. The latter appear to 

 hover always on the brink of starvation, as the islands, which are 

 composed mainly of coral-sand, produce hardly anything of a vege- 

 table nature. While the neighbouring Society islanders have every- 

 thing without labour and in abundance, the unfortunate inhabitant 

 of Tuamotu is forced to support existence with cocoa-nuts, almost 

 the only fruit-trees which will grow on the sandy beach, with 

 fish and shell-fish which are poisonous f y: several months of the 

 year, and often they have to kill their dogs for want of other 

 animal food. There are no birds, except the usual sea-birds ; 

 no quadrupeds, except those brought by man ; no food resources 

 necessary to European life, except what is brought by ships. 

 Although the people are gentle and hospitable, they practise 

 cannibalism, and M. Brandely suggests that it is pitiless hunger 

 alone which has driven them into this horrible custom. These 

 miserable people are the chief pearl-divers of the Pacific ; in- 



their only industry, and women and even children 



take part in it. There is at Anaa, says the writer, a woman who 



>wn twenty-five fathoms, and remain under water for 



three minutes. Nor was she an exception. The dangers of 



the work are great, for the depths of the lagoons are infested by 



gainst which the divers, being unable to escape, are 



v, age battle, in which life is the stake. No year 

 passes without some disaster from sharks, and when one 

 happens all the divers are 'eized with terror, and the fishing is 

 stopped for a time. But gradually the imperious wants of life 

 drive them back to the sea again, for mother-of-pearl is the cur- 

 rent coin of the Tuamotu. With it he buys the rags which 



cover him, the little bread and flour which complete his food, 

 and alcohol, "that fatal present of civilisation," for which he 

 exhibits a pronounced passion. Twenty or thirty years ago the 

 trade in mother-of-pearl in the Tuamotu archipelago was very 

 profitable for those engaged in it. For a valueless piece of 

 cloth, a few handfuls of flour, or some rum, the trader got half 

 a ton of mother-of-pearl worth one or two thousand francs, or 

 even fine pearls of which the natives did not know the value. 

 The archipelagoes were frequented by vessels of all nationalities ; 

 mother-of-pearl was abundant, and pearls were less rare than 

 they are now. The number of trading-ships increased ; there 

 was competition amongst them, and consequently a higher price 

 to the natives, who fished to meet the new demand with im- 

 provident ardour. The consequence is that the lagoons are less 

 productive, and that even the most fertile give manifest signs of 

 exhaustion. The prospect of having the inhabitants of Tuamotu 

 thrown on itshands in a state of helpless destitution, as well as of the 

 disappearance of the principal article of the trade of Tahiti, and an 

 important source of revenue to the colony, alarmed the Colonial 

 administration, and the Ministry of Marine and the Colonies in 

 Paris. Accordingly, M. Brandely was selected to study the whole 

 subject on the spot. The points to which he was instructed to 

 direct especial attention were these : (1) The actual state of the 

 lagoons which produce oysters ; are they beginning to be im- 

 poverished, and if so what is the cause, and what the remedy ? 



(2) Would it be possible to create at Tuamotu, Gambier, 

 Tahiti, and Moorea, for the cultivation of mother-of-pearl, an 



industry analogous to that existing in France for edible oysters ? 

 Would it be possible by this means to supply the natives of 

 Tuamotu with continuous, fixed, remunerative labour which 

 would render them independent, and remove them from the 

 shameless cupidity of the traders ? Could they not be spared 

 the hardships and dangers resulting from the continued practice 

 of diving, and be turned to more fixed sedentary modes of life, 

 by which they might be raised gradually in the social scale ? 



(3) Should the pearl fishing in the archipelagoes be regulated, 

 and, if so, what should be the bases of such regulations ? It was 

 on the mixed economical ami philanthropic mission here indi- 

 cated that M. Brandely went to Tahiti in February last. 

 The statistics did not show any decline in the production of 

 mother-of-pearl, but a careful study on the spot showed that this 

 was due to the great amount of the clandestine traffic, and that 

 the lagoons were growing less productive day by day, that 

 beautiful mother-of-pearl was becoming rarer, and in order 

 now a-days to get oysters of a marketable size, the divers are 

 forced to go to ever greater depths. M. Brandely recommends 

 prompt and vigorous measures be taken at once, as the lagoons 

 of Tuamotu will soon be ruined for ever. The partial steps 

 already adopted have been useless. The total prohibition of 

 fishing in some of the islands for several years has failed, because 

 it has been found that the pintadine is hermaphrodite, and not, 

 as formerly was believed, unisexual. The cause of the im- 

 poverishment of the lagoons is excessive fishing, and nothing else. 

 He thinks that it is possible to create in Tuamotu, Gambier, 

 Tahiti, and Moorea a rational and methodical cultivation of 

 mother-of-pearl oysters, analogous to that existing with regard to 

 edible oysters on the French coasts, and to constitute for the 

 profit of the colony an industrial monopoly which no other 

 country can dispute, for nowhere else can such favourable con- 

 ditions be met with. 



SOCIETIES AND ACADEMIES 

 London 



Royal Society, March 26. — " On the Peculiar B.-!i„viour of 

 Glow Lamps when raised to High Incandescence." By W. H. 

 Preece, F.R.S. 



The experiments described had for their object the investiga- 

 tion of a phenomenon observed by Mr. Edison, who brought it 

 to the author's notice last autumn. Between the limbs of an 

 incandescent filament of a glow-lamp a thin, narrow platinum 

 plate being fixed with an independent wire connection, and a 

 sensitive galvanometer being placed in circuit between the fila- 

 ment and the platinum, a derived current is observed to pass 

 through the galvanometer and through the rarefied space at the 

 bottom of the limb when the main current is increased to a 

 certain strength and the filament reaches a certain degree of 

 incandescence, the strength of the derived current increasing 

 with the increased brilliancy of the glowing filament. In the 

 author's investigations Mr. Edison had made other lamps, in 



