100 



KNOWLEDGE 



[Mat 1, 1899. 



known commercially as " green snail," although it 

 really belongs to a marine mollusc of the genus Turbo, 

 its full title being T. oharlris. These shells, which, when 

 polished, display a mixture of green, yellow, and pinkish 

 pearly tints, are of so large a size that they were formerly 

 mounted as goblets for the Scandinavian kings. They are 

 imported from Peuang, Manila, and -Japan ; specimens from 

 the former locality which weigh from one and three- 

 quarter to two and a-quarter pounds selling at from seven- 

 pence to sevenpence farthing each, while small samples 

 varying between one-half and three-quarters of a pound 

 fetch prices from twopence to threepence each. A second 

 and smaller species of the same genus (T. sartnatiats), 

 commercially termed " turbo " (Fig. 3), is also employed 



FiCr. 3. — The " tiirbo " of the mother-of-pearl trade. 



in the mother-of-pearl trade, although it does not 

 appear to iind a very ready sale. Externally this 

 shell is covered with a black epidermis, beneath which 

 the whole structure is pearly, with a greenish tinge. 

 Commercial samples are generally dead shells, more 

 or less coated internally with a calcareous deposit 

 overlying the pearly layer. These shells, which come 

 from West Africa, are cut into sections, and used for 

 small fancy articles, such as baskets, trays, boxes, etc. ; 

 but they are also worked up into buttons, brooches, and 

 earrings, while they are occasionally employed as pipe- 

 bowls. 



Although seldom quoted in the sales, it may be men- 

 tioned that a beautiful little top-sheU, Trockics (Elcnclnts) 

 iris, used, when polished, by the Maories as an ear-drop, 

 is sometimes employed in the mother-of-pearl trade. 



This completes the list of shells quoted in English trade 

 circulars as mother-of-pearl producers. Nevertheless, as 

 already said, the full amount and value of the imports at 

 the present day are difficult or impossible to obtain, the 

 figures quoted above aflbrd a fair idea of the great im- 

 portance of this branch of commerce. In 1S78 Mr. P. L. 

 Simmonds estimated the average annual imports at between 

 thirty thousand and forty thousand hundredweights 

 (fifteen hundred to two thousand tons), at an approximate 

 value of one hundred thousand pounds. And if the 

 imports are maintained at anything like that level, present 

 prices would indicate a largely enhanced total value. 

 But to the English trade must be added that of other 

 countries, among which America, Austria, and France 

 figure largely, the latter country being reported in 1878 

 to work up annually about thirty thousand hundred- 



weights (one thousand five hundred tons) of mother-of- 

 pearl. In 1870 the French imports were given as one 

 million three hundred and seventy-six thousand one 

 hundred and thirty-two kilogrammes, of the value of three 

 million one hundred and fifty-nine thousand nine hundred 

 and forty-three francs ; this being apparently exclusive of 

 an annual average import of ear-shells to the extent of 

 one hundred and thirty-four thousand five hundred and 

 fifty kilogrammes. 



Some of the uses of mother-of-pearl have been already 

 mentioned, but a few details may be added. Papier-mache 

 inlaying seems to be a decadent art in this country ; nor is 

 this to be regretted, seeing that, from a modern standpoint, 

 it was far from an artistic production. Handles to dessert 

 knives and forks account for a considerable amount of 

 mother-of-pearl, while it is also used to coat card-cases, 

 for fan-handles and the hafts of pocket-knives, as 

 well as for book-covers and countless other fancy articles. 

 Mother-of-pearl, in some instances beautifully carved, was 

 formerly much employed for the tops of snuff-boxes, being 

 sometimes inlaid with tortoiseshell. It is also extensively 

 used by cabinet and piano-makers, and is likewise worked 

 up into boxes, carved brooches and pen-holders. Pearl 

 buttons form a very important item in the trade — the large 

 ones selling at as much as half-a-crown each, while the 

 smaller kinds descend as low as eighteenpence the gross. 

 Whereas in one season pure white may be the fashion for 

 the large buttons, in another the "smoked pearl" of the 

 black-edged oysters or the green pearl of the Japan ear may 

 be solely in demand. 



From its extreme density and hardness, the tools 

 suitable for the worker in mother-of-pearl must be of the 

 finest temper, and acids are often employed to aid in its 

 manufacture, while it is polished with calcined iron- 

 sulphate. Chinese and Japanese workmen are adepts in 

 carving this refractory material, and the beauty and finish 

 of some of their work almost, if not completely, defies 

 imitation by the British artizan. In olden ilays, too, the 

 inhabitants of Polynesia and Melanesia manufactured most 

 beautifully-finished fish-hooks from mother-of-pearl, fine 

 specimens of which are exhibited in the Ethnological 

 Gallery of the British Museum at Bloomsbury. Some of 

 these, from their opalescent green tints, appear to have 

 been cut out of ear-shells, and probably served not only as 

 a weapon to capture fish, but likewise as a bait to lure 

 them to destruction. 



ELECTRICITY AS AN EXACT SCIENCE. 



By HowAKD B. Little. 



in. — Akbitkaey Assumptions and Expressions. Scientific 

 Speculation as opposed to HysTEBLi. 



WHEN one is asked, "What is Electricity?" 

 the wisest course of all is to confess ignorance. 

 The sweeping statement of our old friend 

 Democritus certainly holds good here. Many 

 efforts have been made to formulate a scien- 

 tific definition, and all have been failures. Of these, one 

 of the best I ever heard was a statement to the effect that 

 " Electricity is a particular state of matter." But here 

 there are two imfortunate points — what particular state is 

 not specified, and matter is still, so far as we are concerned, 

 undefined. So that the suggested definition is no definition 

 at all. 



Yet electricity is by no means the only science placed in 

 this position, or remaining in it. We do know that certain 

 causes will always produce definable effects. And, when 



