702 PHILOSOPHICAL TRANSACTIONS. [aNNO 1773. 



attraction of a mountain in France or England, where he thinks some might be 

 found of sufficient bulk for the purpose. This experiment and these remarks 

 were made in the year 1738, or above 30 years ago, yet I believe no similar ex- 

 periment has ever been made in Europe. 



I have made inquiries after a proper hill in this kingdom, for trying so curious 

 an experiment, and have been informed of 2 places in particular, very conve- 

 nient for the purpose. The one is situated on the confines of Yorkshire and 

 Lancashire; where, within the compass of 20 miles, are situated 4 very remark- 

 able hills, called Pendle-hill, Pennygant, Ingleborough, and Whernside, which 

 have been estimated to be from 600 to 750 yards elevated above the plane of the 

 vales between them. By calculation on these data it follows, that the sum of 

 the contrary attractions of Whernside, the largest of these hills, on the plumb- 

 line placed half-way up the hill, would not be less than 30', and might amount 

 to 46", which it is evident is a very considerable quantity, and sufficient to give 

 room to hope for a favourable and satisfactory success of the experiment. The 

 other place pointed out for this purpose, is a valley 2 miles broad, between the 

 hills Helwellin and Skidda, in Cumberland: which hills, according to a plan of 

 them and the adjacent country, communicated by Mr. Smeaton, f.k.s., are ele- 

 vated more than 1000 yards above the intermediate valley By a calculation 

 made according to this plan, the sum of the contrary attractions of the plumb- 

 line, placed alternately on the north side of Helwellin and the south side of 

 Skidda, amounts to about 20'', which is likewise a quantity large enough for the 

 experiment. And though the density of the earth near the surface should be 5 

 times less than the mean density, as there is some reason to suspect, and the at- 

 tractions, as here stated, should consequently be diminished in the proportion of 

 5 to 1 , still the sum of the contrary attractions of Whernside would be 6" or Q", 

 and the sum of the contrary attractions of Helwellin and Skidda would be 4"; 

 which quantities are not too small to be measured and demonstrated by an accu- 

 rate zenith sector, such as that belonging to the r. s., which I made use of at 

 St. Helena, would be, if the fault in the suspension of the plumb-line, which I 

 there discovered, was corrected, in the manner suggested in the Philos. Trans., 

 vol. 54, p. 351. 



XLIX. An Account of Observations made on the Mountain Schehallien for find- 

 ing its Attraction.* By the Rev. Nevil Maskelyne, B. D., F. R. S., and 

 Astronomer Royal, p. 500. 

 In the year 1772, I presented the foregoing proposal, for measuring the at- 



* For this paper Dr. Maskelyne was honoured with the Society's gold medal. And the calculation 

 of the earth's density, from these observations, amply confirmed the expectations and predictions of 

 it ; as fully appears in a future volume of this work. 



