Feb. 17, 1876J 



NATURE 



303 



The few sUver coins of the series weigh about 44 grains, 

 or 2-9 grammes each. The copper coins vary in weight 

 from 43 to 163 grains, or 2'8 to i/'o grammes. 



The Arab systems of money and of weight are treated 

 at great length in Queipo's " Syst^mes Mdtriques et 

 Mondtaires des Anciens Peuples." The earlier gold unit 

 was the dinar, and the later gold unit the viichtal. The 

 dinar was the monetary unit, from the Roman denarizts. 

 The michtal, which signifies weight, was the unit of 

 monetary weight. Oueipo gives a list of 263 gold dinars 

 of the ancient Eastern caliphs which are now in various 

 numismatic cabinets, \vith their weights. No coins were 

 struck by Mahomet and his successors, who used the 

 existing coinage of the countries, until the ySlh year of 

 the Hegira, when both gold and silver coins were struck 

 by Abdelmelik, Caliph of Bagdad. The mean or normal 

 weight of the gold dinar was 66 grains, or 4*25 grammes. 

 This was the weight of the Attic drachma, from which it 

 was evidently derived. There were also gold coins of 

 h h h and 1^ dinar. 



The relation of the weight of the Arab silver dirlum to 

 the gold dinar was as 7 to 10, or nearly as 2 to 3. Queipo 

 gives a list of 592 Arab silver dirhem coins of Arabian 

 caliphs from A.D. 699 to 1195, with the weight of each 

 coin. This varied from about 2'5 grammes in the earlier 

 part of this period up to a maximum weight of 3*1 

 grammes in later times, the mean weight of the dirhem 

 being 2*84 grammes, or 44 grains. He mentions also 

 silver coins of i, ^, and \ dirhem. The half dirhem was 

 thus nearly equivalent to our Saxon penny, the s-Jo*^ o^ 

 a pound of silver, and weighing 22 J troy grains. 



Queipo makes but httle mention of the Arab ancient 

 copper moneys, except to throw a doubt on the existence 

 of the fels as a copper coin, and to assume that it was 

 only money of account, and also that the number of 

 fels in a dirhem expressed merely the number of units 

 corresponding with the value of copf>er in relation to 

 silver. He shows that in the first centuries of the Hegira, 

 the value of silver to gold was as i to 13, and of copper 

 to silver as i to 120. If, therefore, a gold dinar weighed 

 4'25 grammes, its equivalent in copper would weigh 6,630 

 grammes ; and as the mmiber oi/eis in a dinar could not 

 have exceeded 98, that this would give the improbable 

 weight of 67 65 grammes to each copper fels. This was 

 the weight of the Attic drachma, from which it was evi- 

 dently derived. There were also gold coins of J, \, |, 

 and jV dinar. 



The relation of the weight of the Arab silver dirhem to 

 the gold dinar was as 7 to 10, or nearly as 2 to 3. Queipo 

 gives a list of 592 Arab silver dirhem coins of Arabian 

 cahphs from a.d. 699 to 1195, with the weight of each 

 coin. This varied from about 2"5 grammes in the earlier 

 part of the period up to a maximum of 3"i grammes in 

 later times, the mean weight being 2*84 grammes, or 44 

 grains. He mentions also silver coins of \, \, and J 

 dirhem. The \ dirhem was therefore nearly equivalent 

 ,with our Saxon penny, o^th of the pound of silver, and 

 • weighing 22^ troy grains. Queipo makes but httle men- 

 tion of the Arab copper money, except to throw a doubt 

 1 the existence of the /els as a copper coin, and to assume 

 -^t it was only money of account, the number of /els in 

 a dinar expressing merely the number ©f units corre- 

 sponding with the relative value of silver and copper. He 



shows that in the first centuries of the Hegira the value of 

 silver to gold was as i to 1 3, and of copper to silver as i 

 to 120. If a gold dinar weighed 4*25 grammes, its equi- 

 valent in copper would be 6,630 grammes, and as the 

 number oi /els in a dinar could not be more than 98, this 

 would give the improbable weight of 67*65 grammes to 

 each copper /^/j'. 



VAN BENEDEN'S ''ANIMAL PARASITES" 

 Animal Parasites and Messmates. By P. J. Van 

 Beneden, Professor at the University of Louvain, &c 

 (London : Henry S. King and Co., 1876.) 



THIS work forms the twentieth volume of the Inter- 

 national Scientific Series. We believe there was 

 some doubt on the part of the publishers as to the pro- 

 priety of bringing out a popular treatise on so iminviting 

 a subject To have omitted all accoimt of this important 

 series of creatures considered in relation to the welfare of 

 man would, however, have been a serious blunder. It 

 is high time that popular prejudices should be ignored, 

 especially when the welfare of the people themselves 

 is involved in the question at issue. Fully alive to the pre- 

 judices referred to, a writer in Notes and Queries (who was 

 probably anxious to make the subject palatable) says of this 

 little book: "There is as much amusement to be derived 

 from Prof. Van Beneden's pages as there is instruction." 

 We cannot take this optimist view of the matter ; on the 

 contrary, we fail to find anything amusing in the book, 

 although, as might be expected from the author's known 

 position as a man of science, there is much to be learnt 

 from an attentive study of the text. Prof. Van Beneden's 

 strength lies in a clear exposition of the phenomena of com- 

 mensalism. We owe to his remarkable zoological acumen 

 the correct interpretation of those singular phases of 

 parasitic life which he has so happily classed under the 

 role of Messmates and Mutualists, respectively. On 

 this head he has strung together such a multitude 

 of facts that his work cannot fail to be useful to 

 working naturalists. Whether the general reader 

 will find anything " amusing " in these pages is very 

 doubtful. He may, indeed, if his mind be stfll do- 

 minated by the teachings of a certain school, find 

 comfort in the assurance which M. Van Beneden 

 affords that the welfare of all the most repulsive forms 

 of insect life is most carefully looked after. WTiat 

 a comfort it must be for the poor Cayenne convict 

 when tortured by insect parasites to know that the ever- 

 helping " Hand " superintends the " preservation " of the 

 larvae of Lucilia hominivora with the same care that it 

 does " the young brood of the most brilliant bird." 

 Surely the Mexican soldier who " had his glottis de- 

 stroyed, and the sides and the roof of his mouth rendered 

 ragged and torn, as if a cutting punch had been driven 

 into those organs," could hardly be brought to realise 

 the need-be for such a process of development on the 

 score of benevolence towards this frightful parasite ! 

 The case of Lucilia is by no means exceptional, since 

 there are scores of parasites, both external and internal, 

 that are capable of inflicting the most terrible sufferings 

 aUke upon man and beast Push our authors Bridgwater- 

 treatise-like views to their logical outcome, and it neces- 

 sarily follows that every pang endured by countless 



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