sect. iv.] DISSERTATION SECOND. 167 



himself, who measured his base over again, and also the 

 angles of the triangles. He died, however, before he could 

 publish the result. Muschenbroek, who calculated the 

 whole anew from his papers, came to the conclusion just 

 mentioned, which, of course, was not known till long after 

 the time when the measure was executed. No advantage, 

 accordingly, was derived to the world from this measure- 

 ment till its value was lost in that of other measurements 

 still more accurately conducted. 



A computation which, for the time, deserves considera- 

 ble praise, is that of Norwood, in 1635, who measured the 

 distance between London and York, taking the bearings 

 as he proceeded along the road, and reducing all to the 

 direction of the meridian, and to the horizontal plane. The 

 difference of latitude he found, by observation of the solsti- 

 ces, to be 2° 28', and from that and his measured distance, 

 he concluded the degree to be 367, 176 feet English, or 

 57,800 toises. This has been found to be a near approxima- 

 tion ; yet his method was not capable of great accuracy, 

 nor did he always execute it in the best manner. " Some- 

 times," says he, " I measured, sometimes I paced, and I 

 believe I am within a scantling of the truth." 



Fernel, a French physician, measured with awheel from 

 Paris to Amiens, which are nearly in the same meridian, 

 and he determined the degree from thence to be 56,746 

 French toises ; a result which falls short of the truth, though 

 not very considerably. 



These investigations, it is plain, could not but leave con- 

 siderable uncertainty with respect to the magnitude of the 

 earth. The Academy of Sciences became interested in 

 the question, and the measurement of an arch in the meridi- 

 an was undertaken under its auspices, and executed by the 

 Abbe Picard, already known for his skill in the operations 

 of practical geometry. He followed a method similar to 



