36^ 



CATALOGUE, — PRACTICAL ASTRONOMY, GEOGRAPHY. 



P, P. on the figure of the earth, and on sphe- 

 roidal triangles. Nich. VIII. 12, 151. 



Rcmatks on Playfaii. 



Spheroidal triangles. See Navigation. 



Account o/Major Mudge's paper on the Measurement of 

 an Arc of the Meridian, extending from Dunnose, in 

 the Isle of mght, latitude 50° 37' 8", to Clifton, in 

 Yorkshire, latitude 53° 27' 3l", in courseof the opera- 

 tions carried on for the Trigonometrical Survey of Eng- 

 land, in the years 1800, 1801, and 1802. From the 

 Journals of the Royal Institution. II. 

 In the course of these operations, a new base had been 

 measured on Mistcrton Carr, and from its length, compared 

 with the former trigonometrical measurements. Major 

 Mudge was enabled to calculate the magnitude of a degree 

 of the meridian, with well grounded hopes of very great ac- 

 curacy. The result, however, of these calculations indicates 

 an irregularity, which could not possibly have been foreseen, 

 although it has happened in a still greater degree in some 

 former measurements. The northern part of the arc, 

 which, upon the supposition of the ellipticity of the terres- 

 trial spheroid, ought to be less curved than the southern, 

 and to exhibit the length of the degree greater in the same 

 proportion, appeared from the observations to be more 

 curved, the mean of the whole arc giving the degree 42 

 fathoms smaller than the arc between Dunnose and Arbury 

 Hill. Major Mudge thinks it improbable that the error of 

 observation can be one tenth as great as this difference im- 

 plies, and he conjectures that the plurab line must have been 

 deflected at Clifton as much as 8" or lo" southwards, by the 

 irregularity of the terrestrial attraction. This opinion was 

 confirmed, by a comparison of his observations with those 

 which had been made at Blenheim, giving 60884 fathoms 

 for the length of the degree in latitude 51° 13', deduced 

 from the meridional distance of Blenheim from Dunnose. 

 The arc from Dunnose to Clifton gives 60820, in latitude 

 Hi" 2* 20"; from Dunnose to Arbury Hill, 60865, in lati- 

 tude 51° 35' 18". By comparing the latitudes and distance 

 of Clifton and Barcelona, we have 60795 "for the degree in 

 latitude 4J° 24', the whole arc being somewhat more than 

 twelve degrees; and at the middle point between the parallel 

 of Clifton and Paris, the degree appears to be 60825 fa- 

 thoms, in latitude 51° 9'. Major Mudge promises to give 

 to the Royal Society, at a future time, an account of the 

 further prosecution of his optrations for continuing the tri- 



gonometrical survey, which has hitherto been conducteil 

 on so extensive a scale. Y. 



Tabular comparison of Observations. 

 Length of a degree, on the Level of the Sea. 



Latitude. Toises. 



66° 20' N. 

 66° 20'l2' 



(52° 46' 

 50° 41' 



50° 9 27" 

 49° 23' 



49° 7' 



4a'' 3' 



(57422 



57419 



5707* 



57064.5 



Fathoms 

 according 

 to Roy. 



61194.3 Maupertuis, 1736 — 7.) 

 ;8 Melanderhielm and Svan- 



berg, 1802. 

 Norwood, published 1036.) 

 0C840 Roy. 1790. The degree 

 perpendicular to the 

 meridian 61182.3, fa- 

 thoms. Ph.tr. 1795. 

 60826.6 



Maupertuis and Cassini, 



1739 — 40. 

 Picart. 



60833.0 Mean of Maupertuis and 

 Cassini and Liesganig. 



