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THE POPULAR SCIENCE MONTHLY. 



in place of the cotton-cloth that had hitherto 

 served as money, with cowries, at the rate 

 of four thousand to the dollar, for small 

 change. A large demand for cowries sprang 

 up, and the trade in them was stimulated to 

 such an excess that the market was glutted, 

 and it afterward languished for several years. 

 The present demand is quite lively. The 

 cowrie-shell is used as currency principally 

 in the countries near the Niger, except in 

 Ashantce, where gold-dust is the medium of 

 exchange. North of Ashantee, gold-dust and 

 the gera or cola-nut (Sterculia acuminata) 

 are used with cowries, a load of sixty pounds 

 of the nuts being considered equivalent in 

 value to about fifteen thousand cowries. 

 The shells have been used as a medium of 

 exchange from a high antiquity. Marco 

 Polo found them circulating in Yunnan in 

 the thirteenth century ; and they have been 

 discovered in prehistoric graves in the Bal- 

 tic countries. Herr A. Wormann says, in a 

 paper of the Hamburg society, on trade by 

 barter in Africa, that a variety of objects 

 besides cowries serve as measures of value 

 in the different countries of that continent. 

 Among them are pearls, little Nuremberg 

 looking-glasses, iron, copper, brass, cloth, 

 salt, tobacco-leaves, writing-paper, the cola- 

 nut, goats, horses, cattle, and slaves ; and 

 the regions in which each of these articles 

 circulates are defined by fixed limits. Iron 

 and copper from Egypt circulate in the up- 

 per Nile region ; Maria-Theresa thalers and 

 cowries in Soodan ; cowries, pearls, and 

 " Mericani " (unbleached goods) on the East 

 coast and in the region of the Arab trade. 

 South and west of these countries are distinct 

 trade-regions that have no direct connection 

 with them, in each of which a different cur- 

 rency is needed, although ivory and slaves 

 are the only products. 



Shooting - Stars, their Traditions and 

 their Origin. The appearance of comets 

 and shooting - stars announced to the an- 

 cients and to our ancestors the death of 

 some grand personage or some woe, and the 

 chronicles are full of notices of such phe- 

 nomena. The notices are, in fact, occasion- 

 ally so numerous as to be suspicious, for, as 

 Lubienietz remarks in his "Cometography,'' 

 when an event of such a kind happened, it was 

 thought there must have been a comet about 



the time, and so it was put down ; and an 

 amusing picture has been made of the per- 

 plexity of a cometographer who could not 

 find any comet for seventeen years, portent- 

 ous of the events that were to happen during 

 that period. The Chinese records are more 

 trustworthy, for their observers were con- 

 stantly at their posts, and formed a regu- 

 larly and scientifically organized body. The 

 documents recording the observations were 

 specially preserved ; for the Chinese, from a 

 time many centuries before the Christian 

 era, attributed to the different stellar groups 

 a direct influence on the different provinces 

 of their country. As shooting-stars may be 

 seen at almost any time, it was to be ex- 

 pected that a great number of notices of the 

 phenomena must have been recorded during 

 the forty centuries of which we have a lit- 

 erature of some kind. Plutarch, in his biog- 

 raphy of Lysander, makes a near approach 

 to the modern explanation of the origin of 

 these bodies, saying, "Some philosophers 

 believe that the shooting-stars are not de- 

 tached parts of the ether which go out in 

 the air soon after they have been inflamed, 

 that they no more originate in the combus- 

 tion of the air which is dissolved in great 

 quantity in the upper regions, but that they 

 are rather falling celestial bodies." The 

 general opinion is, that shooting-stars are 

 bodies of small dimensions that circulate, 

 under the influence of attraction, among the 

 planets in the same way as the planets them- 

 selves. When they cross our atmosphere, 

 the friction develops heat enough to consume 

 them, most frequently before they reach our 

 soil. The mean height at which the mete- 

 ors become luminous exceeds, however, the 

 estimated height of our atmosphere. Pois- 

 son has, therefore, suggested that, as they 

 could hardly have become inflamed from 

 friction at such a height, an atmosphere of 

 neutral electricity may exist considerably 

 beyond the mass of the air which is subject 

 to the earth's attraction, and is disturbed 

 by the entrance of the meteors, so that they 

 become electrified and incandescent. Any 

 theory to account fully for the origin of shoot- 

 ing-stars must explain the periodic swarms. 

 For this reason, the theory of ejectment 

 from lunar volcanoes must fail, even were 

 it not otherwise shown to be baseless. M. 

 Faye accounts for the August meteors by 



