COMPARATIVE METROLOGY. 387 



That his calculation of its profitableness refers to an extent of 7 

 jugera as that in which it would be proper to employ one vine- 

 dresser, is a curious instance of the existence of the idea that 

 this extent of land is the proper allowance for one person. 

 Here we have the old allowance passing into the modern rub- 

 bio. It is useless to look for much accuracy in such matters, 

 but if we take Pliny's statement that the regular allowance of 

 wheat seed was 5 modii, and assume that the amphora was 26 

 litres, which agrees with Cagnazzi's^ value of the Roman pound 

 in French grammes, and if we also adopt the common statement 

 that the modius is one-third of the amphora, then 35 modii (the 

 allowance for a rubbio) will be 30 decalitres and a third, which 

 agrees very closely with Prony's value of the rubbio of wheat. 

 That of oats is yet more nearly equal to 4 modii. The perpetu- 

 ation of the traditionary allowance of seed is in the former case 

 more close than we could have expected. It amounts to some- 

 thing less than 2 bushels the acre, and is therefore under the old 

 practice in England and in Cisalpine countries generally. 



10. The divisions of the acre appear to have grown out of 

 those of the pezza. It is divided first into 4 roods as the other 

 into 4 quarta, and the 40 perches of the rood correspond to the 

 40 ordines of the quarta. But with us so small a division as the 

 staggiolo was useless, and the perch becoming practically the 

 smallest measure seems to have been regarded as a square. 

 Properly it was 30 square yards, but for convenience it was 

 increased by a quarter of a yard, so that its side became 5 yards 

 and a half. This has been already noticed. I repeat it now 

 because it leads to the history of the English mile, which got its 

 name from being not much unlike in magnitude the Roman 

 mile ; though it is said not to be formally recognized in any- 

 thing earlier than an act of Elizabeth, What we call a furlong 

 is properly a fiiiing, or 4th part. Why then is it the 8th part of 

 a mile ? The answer is, that the original unit was the long acre, 

 that is, an acre consisting of perches arranged in single file. 

 One hundred and sixty times 5 yards and a half make eight 

 hundred and eighty, which is said to be the length of Long Acre 

 in London. The furlong was therefore the long rood, and we 

 have thus an instance in which a measure of length has sprung 

 out of one of surface. Perhaps the word rood has relation to the 



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