24< Mr. Galloway's Remarks on FernePs Measure of a Degree. 



which is 278 yards shorter than the Italian mile of Dr. Ber- 

 nard, and 225 yards shorter than the old Roman mile, with 

 which jVIr. De Morgan states (I think on good grounds) that 

 the Italian mile was commonly though vaguely supposed iden- 

 tical. The difference is so great, and the result so much at 

 variance with all the other authorities which have been pro- 

 duced, and which concur in giving the Italian mile longer than 

 the Roman mile, that if we admit the hypothesis we are driven 

 to the improbable conclusion that Fernel, without intimation, 

 laid down an arbitrary foot for himself, thereby rendering his 

 statements unintelligible or deceptive. 



There is another statement of Fernel's, which though of no 

 value towards giving the exact length of his degree, may 

 perhaps go for something when the question turns upon a 

 difference of 16 miles in 70. He states that the northern 

 extremity of his arc was reckoned by the country-people to 

 be 25 leagues distant from Paris. Now it is not here ma- 

 terial to inquire what the length of the league was. We 

 know from the difference of latitudes that the distance in a 

 straight line was somewhere about 70 English miles, and it 

 cannot be supposed that the vulgar estimate was in error to the 

 extent of anything like 16 miles. But as Fernel manifestly 

 supposes his own determination was not at variance with the 

 vulgar estimate, it is difficult to believe that he gave his re- 

 sult in terms of a scale by which the reputed distance must 

 have been reduced nearly a fourth part. Amiens, from which 

 it has generally been supposed he measured, is 75 miles from 

 Paris by the road. 



I may also add, that if the hypothesis be correct, Fernel's 

 notions of a degree, before he attempted to measure it, must 

 have been very extraordinary. In the same work in which the 

 figure occurs (Monalosphatrium, p. 15) there is a proposition 

 explaining the method of measuring the terrestrial distances 

 between places, in which he directs 60 Italian miles to be al- 

 ' lowed for each degree of latitude, and one mile for each mi- 

 nute, and gives some examples of distances socomputed. But 

 according to the hypothesis his Italian mile of 5000 geome- 

 trical feet was only 1389 English yards, whence he must have 

 supposed the degree to be less than 47|- English miles. This 

 is surely without the limits of credibility. 



It is proper, however, to remark, that Riccioli, in his Geo- 

 graphia Reformata, lib. ii. c. 2, mentions Fernel's diagram, 

 and gives the ratio of its length to the ancient Roman foot, 

 whence it may be inferred that he regarded it as intended for 

 the representation of an absolute measure ; but Riccioli al- 

 lows no authority either to the figure or to the statements of 



