[ 22 ] . 



III. Further Remarks on Fernel's Measure of a Degree, in 

 Reply to Professor De Morgan's Letter in the Number for 

 May. By Thomas Galloway, A.M., F.R.S. 



To the Editors of the Philosophical Magazine and Journal. 



Gentlemen, 

 OO long as the argument relative to the length of Fernel's 

 degree of the meridian turned upon a standard of measure 

 derived from the human body, or the length of a man's walking 

 pace, I saw little reason for adding any thing to my former 

 communication, being satisfied that a result expressed in terms 

 of such a standard would bear any interpretation (at least 

 within wider limits than would include the differences under, 

 discussion) that any one might choose to give it ; but the new 

 evidence which has been produced by Prof. De Morgan in your 

 Number for May, changes entirely the state of the question. 



The conclusion at which Mr. De Morgan has ultimately 

 arrived is founded on two assumptions : first, that the diagram 

 or figure in the Monalosphccrium is, or originally was, a copy 

 of a foot-length as laid down on a scale ; and secondly, that 

 Fernel used the same or an equivalent foot in measuring the 

 diameter of the wheel of the vehicle in which he travelled from 

 Amiens (or wherever his station was) to Paris. With re- 

 spect to the second assumption there is no evidence what- 

 ever ; and on looking at the copy of Fernel's work in the British 

 Museum, I think there are strong reasons for doubting the ac- 

 curacy of the first. Fernel does not say that his diagram was 

 intended to define the length of the geometrical foot, or that it 

 corresponded in dimension with any actual scale ; on the con- 

 trary, there is no allusion to it in the text at all, and unless the 

 title printed under it, " Figuratio pedis geometrici," beheld 

 to have reference to magnitude, there is nothing to lead us to 

 infer that he had any other object in view than simply to re- 

 present by a diagram the divisions which should be cut on a 

 measuring rod. The pj)rt of the work in which the passage 

 occurs is a treatise on Mensuration ; and in describing the mea- 

 suring rod he remarks that it should be selected with great 

 pains, " omni molimine" (referring probably to the accuracy 

 of the division), and enriched with a diversity of measures, 

 " mensurarum diversitate locupletata ; " that it should be five 

 feet in length, and marked with the divisions expressed in the 

 following table, viz. four grains = a digit, four digits = a 

 palm, four palms = a foot, five feet =a a pace. The diagram 

 shows all those divisions of the foot ; but there seems to me 

 no more reason for supposing that they were intended to be 



