^3 



Analysei of Booh, 



France, from Dunkirk to the Mediterranean. They even con- 

 tinued the measurement to Barcelona ; and in 1806 Biot and 

 Arrago continued it as far as Formentera, the fartliest south of 

 the Balearic islands. In the year 1801 the measurement formerly 

 made in Lapland was repeated with great care and skill by three 

 members of the Swedish Academy, And about the same time a 

 similar measurement was made by Major Lambton on the Coro- 

 mandel coast. All these measurements agree with each other in 

 making the earth an oblate spheroid, and in showing that the 

 length of a degree is continually increasing as we advance from 

 the equator to the pole. 



But about the same time another measurement was made in 

 England of 2° 50', which totally disagreed with ail the others, 

 and which represented the length of a degree as dimir)ishi])g in- 

 stead of increasing from the equator to the pole. Tliis sineasure- 

 ment was made by Lieut. -Col. Mudge, a gentleman perfectly 

 well qualified for the undertaking, and with instruments of the 

 most perfect construction that had ever been finished by any 

 artist. Various opinions were formed about the cause of this dif- 

 ference. Some philosophers were disposed to give up the elipdc 

 figure of the earth altogether, and to consider it as h body of an 

 irregular shape. Otiiers, and among these was Col Mudge him- 

 self, conceived that it might be owing to local attractions, oc- 

 casioning a deviation of the plumb-line. The object of this 

 paper is to show that the want of coincidence in Col. Mudge's 

 measurement with that of the other measurements, was owing to 

 errors committed in determining the latitude of the places, par- 

 ticularly of Arbury-hill, which lay about half way between the 

 two extremities of the arc measured. This proposition Don 

 Rodriguez makes out in a satisfactory manner. His reasoning 

 indeed is founded on the elliptic hypothesis ; but he shows that 

 no supposed alteration in the eccentricity can produce any mate- 

 rial variation in bis conclusions. He deduces 5/074 toises as the 

 mean length of the degree in the latitude measured by Colonel 

 Mudge. This subject deserves the closest attention of philoso- 

 pliers. We do not see why the astronomical observations of 

 Col. Mudge might not be repeated. If an error in them could 

 be detected it would go far to set this difficult and long agitated 

 question at rest, 



Don Rodriguez concludes his paper by drawing the attention 

 of English philosophers to the measurement of arcs of the meri- 

 dian in the southern hemisphere. At present we are possessed 

 of only one measurement of this kind, that of Lacaille at the 

 Cape of Good Hope, and it by no means agrees v^'ith similar 

 measurements in the nortliern hemisphere. Hence it has been 

 conceived by some that the northern and southern hemispheres 

 have different eccentricities, Lacaille's measurement should be 



