330 SOME THOUGHTS ON 



or that any of them would have been unable to give the required 

 information. They were certainly not all Frenchmen. Scar- 

 pellini, the only person whom Prony mentions, and whom he 

 speaks of with respect, being, beyond all question, one of them. 

 Was he ultimus Romanorum? the last person who knew the 

 length in metres or French feet of a measuring chain? and 

 might not Niebuhr have borrowed one from any village land- 

 surveyor and measured it himself? Niebuhr's result is that the 

 pezza is equal to 24,716 square feet and a fraction. It is not 

 said what foot he means ; most probably the French foot, which 

 is the longest of any he was at all likely to make use of, and it 

 is therefore worthy notice that even so his estimate is too small. 

 I am obliged to do these things in my head, but a simple piece 

 of mental arithmetic enables one to see that the pezza is much 

 more than 25,000 French feet. Prony's statement, which does 

 not differ from that of the tables, if at all, except by the cor- 

 rection of an almost inappreciable error (I know not if this error 

 affected the particular result in question) is, that the pezza is 

 equal to 2640*6257 square metres. Neglecting the last decimal, 

 it follows that the pezza is 10 times the square of 1 6 J metres. 

 Hence if we assume the pezza to be 25,000 feet, 100 linear feet 

 will be 32 '5 metres ; a result which exceeds the truth by about 

 the 2000 th part. Consequently the pezza is more by about 25 

 feet than 25,000 feet, and consequently Niebuhr's calculation, 

 if he meant the French foot, is in defect by about 300. When 

 we come to his calculations of the jugerum, another difficulty 

 arises, namely, his not having mentioned what value he assigns 

 to the ancient Eoman foot. According to Boeckh, Niebuhr has in 

 his history expressed a strong opinion in favour of Cagnazzi's 

 determination. Whether he had formed it at the date of the 

 letter of which I am speaking, I do not know. Certain it is that, 

 if we adopt this value, which is higher than the average, Niebuhr's 

 determination of the size of the jugerum errs in excess as that of 

 the pezza in defect ; and, the latter being the larger measure, both 

 errors tend the same way, namely, to make the pezza and the 

 jugerum appear more really equal than they are. The value in 

 question is 131*325 French lines, and the result is that the 

 jugerum is something less than 24,000 feet. Niebuhr makes it 

 24,310 feet and a fraction. Thus unless I am greatly mistaken, 

 the difference between the two measures instead of being scarcely 



