Mr. Galloway's Remarks on Fernel's Measure of a Degree. 97 



of Budaeus, De Asse, &c., had been recently published ; and ac- 

 cording to Snellius (Em/OS. Bat., p, 132), Budeeus expressly 

 makes the Roman foot the same as the Pied de Roi. Fernel 

 was not likely to be better informed, and in such case could 

 have no reason for stating the dimensions of his wheel in terms 

 of a foreign standard. 



With respect to the statement of Weidler, on which Mr. 

 De Morgan has raised some questions, namely, that Fernel's 

 measure was finished in 1550, Lalande's remark may be re- 

 garded as a satisfactory reply : c'est encore une errenr. 



Although I have already trespassed too far on your space, 

 it would scarcely be right to close these remarks without 

 observing, that neither Picard, Montucla, Lalande, nor De- 

 lambre attach the slightest value to Fernel's measure, but 

 all concur in representing the accuracy of the result as a 

 matter of mere accident. A ruder and more inadequate ope- 

 ration it would, in fact, be difficult to imagine. He begins 

 by observing the sun's meridian altitude sotnewhere in Paris, 

 on the 25th of August (the year is not mentioned) ; he then 

 sets out to travel northwards (it is sujjposed on the road 

 to Amiens) ; on the 28th he observes again, and finds that he 

 has not yet reached a degree, but the observation enables him 

 to see how far it would be necessary to travel on the followino- 

 day. Having gone this distance, he finds himself on the 29th 

 exactly a degree to the north of Paris. His observations of 

 altitude are only given to minutes, and DeJanibre shows that 

 in allowing for the sun's motion in declination he made an 

 error of 2', which alone would vitiate the result to the amount 

 of 1900 toises. He gives no indication whatever of the place 

 at which he stopped, so that no means exist of estimating the 

 amount of his error with respect to the celestial arc. Picard 

 says it was S' 24", but this supposes that he proceeded all the 

 way to Amiens, which is very doubtful. He then mounts a 

 waggon going direct to Paris, and counts as he proceeds the 

 revolutions made by the wheel during the journey. By what 

 means he thought himself enabled to make any probable esti- 

 mate of the reduction necessary on account of the turnings and 

 acclivities of the road, is beyond comprehension. However, 

 he fixes upon 17,02t revolutions. He then compares his re- 

 sult with that of the Arabians ; and from some conjectures 

 (the grounds of which have been stated) concludes the Ara- 

 bian degree to be 31-0,000 feet. His own determination was 

 340,480 feet; an agreement which Snellius roundly asserts 

 he never would have obtained from his rude geodesy. For 

 these reasons, most of those wlio have described his operation 

 have expressed a suspicion that he took his result froua the 

 Phil. Mag. S. 3. Vol. 20. No. 129. Feb. 1842. H 



