X)0 FIGURE Or THE EARTH.' 



or porcelain vessels, which fluat of ammonia has the property 

 of corroding. 



(To be Continued) 



II. 



Observations on the Measurement of three Degrees of the 

 Meridian conducted in England by Lieut. Col. liyilliam 

 Mudge, By Don Joseph Rodriguez. From the Philoso- 

 phical Transactions for 1812. p. 321. 



(Concludedfrom p. 334, Vol. XXXIII.) 



The uncertain- But to return to our subject of the English measurement. 



ty which may jf the uncertainty which yet subsists, with respect to the exact 

 subsist respect- ,, ~ . !■_».».. • m 



ing the figure, "gure ot the earth and its dimensions, occasions some small 



&c of the errors in the calculation of the series of triangles, the sum of 

 affect'the entire tnese eriors W M be found in the estimate of the entire arch, 

 arc propor- and will increase in proportion to the extent of the arc mea- 

 thsm any^art sure( ^* Now, in the English measurement, we find exactly 

 of the same; the reverse of this. For the difference between the results of 

 trarv ^annens calcu l at ion and observation is only l",38 on the whole arc j 

 in the English but is even as high as 4",77 on one or * tne smaller arcs. So 

 measurement : t j ia ^ whatever error we may suppose to have been introduced 

 into the calculation, by assuming a false estimate of the sphe- 



. roidity of the earth, or of other elements employed in the 



■which shews ..... . , , , . . .. - 



a considerable calculation, it is very evident that the zenith distances ot stars 



error of ano- taken at Arbury Hill are affected by some considerable error, 



theobs. wholly independent of these elements. 



It was not till the date of the measurement of the meridian 

 in France, that M. Delambre published and explained, with 

 admirable perspicuity and elegance, all the formulae and me- 

 thods relative to the calculation of spheroids, and put it in the 

 power of astronomers in general to make use of the elliptic 

 elements in verifying the results of their observations. In the 

 present state of science these elements are well known, and 



.,,, the errors that can arise from any uncertainty in them, are 



I he errors y / 



from uncer- not so considerable as is generally supposed. The oblateness 



tai.nty mthe and the diameter at the equator are the only elements want- 

 elliptic ele- . ,,. / i r ■ , ^ 

 mcnts are not ing in the calculation 3 for the purpose of seeing what effect 

 «on*iderabIe. our 



