PEARL 



827 



rarity of accidents from sharks, usually so abundant 

 in tropical seas, is to be attributed to the bustle and 

 to the excitement of the waters during the fishery 

 frightening away those dreaded creatures. The 

 divers are sometimes paid fixed wages, others agree 

 for one-fourth of the produce. When a boat-load of 

 oysters lias been obtained it returns to shore, and 

 the cargo, sometimes amounting to 20,000 or 30,000, 

 is landed and piled on the shore to die and putrefy, 

 in order that the pearls may be easily found. 

 In Ceylon, in 1889, in twenty-two days fifty divers 

 brought up 11 million oysters, which sold for 24s. 

 per 1000 shells, the government receiving 10,000 

 and the divers 3200. When the animals in the 

 shells are sufficiently decomposed the washing 

 commences, and great care is taken to watch 

 for the loose pearls, which are always by far the 

 most valuable ; the shells are then examined, and 

 if any attached pearls are seen they are 'handed 

 over to the clippers, who, with pinchers or ham- 

 mer, skilfully remove them. Such pearls are only 

 used for setting ; whilst the loose ones, being usu- 

 ally quite round, are drilled and strung, and can 

 be used for necklaces, &c. 



The pearls vary much in size ; those as large as a 

 pea, and of good colour and form, are the best, 

 except unusually large specimens, which rarely 

 occur, the most extraordinary one known being 

 the pearl in Mr Beresford Hope's collection at 

 South Kensington, which measures two inches 

 in length, and four in circumference, and weighs 

 1800 grains. The smaller ones are sorted into 

 sizes, the very smallest being called seed-pearls. 

 A considerable quantity of these last are sent to 

 China, where they are said to be calcined and used 

 in Chinese pharmacy. Amongst the Romans the 

 pearl was a great favourite, and enormous prices 

 were paid for fine ones. The single pearl which 

 Cleopatra is said to have dissolved and swallowed 

 was valued at 80,729 ; and one of the same value 

 was cut into two pieces for earrings for the statue 

 of Venus in the Pantheon at Rome. 



The finest pearls are found within the mantle of 

 the mollusc, close to the lips of the shell, or in the 

 soft part of the oyster near the hinge of the shell ; 

 tlir nrst pearls are tliose found within the close, 

 coarse fibres of the adductor muscle. At intervals 

 they are found loose in the shell outside the body of 

 the oyster, and may when large get washed out of 

 the shell and thus be lost. Lastly, pearls are often 

 found embedded more or less deeply in the shell, 

 having in some cases escaped from the soft tissues. 

 It is notable that the adherent pearls occur almost 

 invariably in the flat or lower valve ; occasionally, 

 it is true, they are found embedded in the rounded 

 or upper valve, but in such cases it is observed 

 that the shell has been found lying at the bottom 

 in the re'veree position. The pearls found embedded 

 in or under the ' muscular .impression ' are always 

 small, irregular, and worthless, similar to those 

 found embedded in the adductor muscle itself. 

 Pearls are found in infinite variety of form, and 

 the consecutive layers vary in brightness, colour, 

 and perfection. The most highly prized pearls are 

 quite spherical, and it is evident from their shape 

 that these must have been formed free in the 

 mantle or in the soft tissues of the mollusc, and 

 not cemented to the shell. Some pearls show 

 defects caused apparently by the contact of new 

 foreign sul>stances, organic or inorganic, such as a 

 grit or film of weed : and in some cases it requires 

 a number of layers to completely hide these defects. 

 Thus every new layer secreted changes the value 

 of the pearl. When a pearl that has been cut from 

 the shell presents a hemispherical surface, it is 

 sometimes called a ' perle Unit on ; ' such a pearl is 

 flat on one side, and rounded or convex on the 

 other. If a solid pearl has an irregular shape, 



8 



tl 



having grown over a rough object, it is known as 

 a baroque pearl. Sometimes warty pearls are 

 hollow, and pass under the name of 'coq de perle.' 



Pearl-oysters frequently renovate their shells, 

 and are in the habit of burying such intruders as 

 they cannot otherwise dispose of. Stones, mud, 

 small shells, wood, and especially layers of weed 

 are found thus embedded in shells forming unnat- 

 ural excrescences on the surface. These protuber- 

 ances are gradually removed by the oyster secreting 

 thinner layers of nacre on the top of them than on 

 the base until the surface becomes again level. 

 Slowly, but steadily, the exterior surface of the 

 shell decays and disappears, until the foreign sub- 

 stance, of whatever nature it may be, comes within 

 the reach of advancing dissolution, and thus the 

 oyster literally passes a stone or other intruder 

 through its shell. In the Natural History Museum, 

 South Kensington, and in the Museum of Practical 

 Geology in Jermyn Street there are specimens 

 which clearly illustrate the processes of relming the 

 shell and of burying foreign substances. They are 

 flat shells (the lower valves), with a number of 

 the figures of Buddha lying embedded at equal 

 distances apart, on the upper portion of the shell 

 near the lips, but not so deeply buried as to lie 

 hidden. These are produced artificially in China ; 

 the little figures are slipped carefully below the 

 mantle of the oyster, and the process of deposition 

 covers them with nacre. 



The value of a pearl depends upon its size, shape, 

 colour, brightness, and freedom from defects. The 

 most valuable pearls at the present time are tliose 

 which are perfectly round; the button -shaped 

 ranks next, and then comes the drop or pear-shaped 

 pearl. Perfectly round pearls over 25 grains in 

 weight are extremely scarce, and secure high 

 prices. They are greatly sought after to form 

 the centre of necklaces, and large pearls of this 

 character are safe and very profitable investments. 

 The varying tints and colours of pearls are less 

 difficult to understand than some of their eccentri- 

 cities of growth. The changing condition of the 

 sea, both as regards purity and temperature, the 

 health of the oyster, accidents, such as the dis- 

 charge of the inky fluid of the cuttle-fish in the 

 neighbourhood of the oyster, all will probably affect 

 the colours of the successive growth-periods of the 

 pearl. Pearls, when of extraordinary beauty, size, 

 and brilliancy, will sell for sums which appear 

 extravagant. 



The chemical composition of the pearl is carbon- 

 ate of lime associated with a small proportion of 

 organic matter. It is easily affected oy acids and 

 fetid gases, and may be calcined by exposure to 

 heat. Its sp. gr. is 2'5 to 2'7. Three varieties of 

 pearls being examined, British, Australian, and 

 Singhalese, the qualitative analyses showed that 

 they all had an identical composition, and that 

 they consisted solely of water, organic matter, and 

 calcium carbonate. There was a total absence of 

 magnesia, and of all the other mineral ingredients 

 of sea-water, from which the inorganic part of 

 pearls must of course be obtained. 



The most important marine pearl-fishery on the 

 American continent is that of Lower California, 

 the central point being at La Paz. The largest 

 and finest black pearls which come into the market 

 are the specialty of these fisheries. In Australian 

 waters pearls are fished on the coast of West 

 Australia and of Queensland, and in Torres Strait. 



River -pearls are produced by fresh-water mussels 

 in Scotland, Wales, Ireland, various parts of Russia, 

 Germany, Canada, and the United States. British 

 pearls are spoken of by Tacitus and Pliny ; and in 

 the end of the 17th century the Scottish pearl- 

 industry was of some importance. The Spey, Tay, 

 South Esk, Boon, Dee, Don, Ythan, and Forth have 



