Mr. Nixon on the Heights of the Hills of Dent, fyc. Yorkshire. 83 



it becomes necessary, in order to inspire confidence, to give 

 every needful particular respecting the bases, signals, instru- 

 ments, and methods of calculation. 



Bases. — From the third volume of the Trigonometrical Sur- 

 vey of England and Wales, are extracted the following di- 

 stances between stations, &c. placed on hills forming part of 

 the above group. 



Ingleborough to the Calf 77,615 feet. 



Ditto Shunnor Fell . . 82,397 



Ditto Pen-y-gent Rock 32,124 



Ditto Whernside . . . 22,435 



Shunnor Fell to the Calf 59,487 



On the Calf were found the stakes which had supported the 

 theodolite used in the Ordnance Survey. Shunnor Fell was 

 not visited, but the signal now on its summit has most pro- 

 bably been erected over the proper station-mark. In the centre 

 of the pile of stones yet remaining on the highest point of 

 Whernside, there stood some years ago a signal-staff' known 

 to have been erected by Colonel Mudge's party. The rock 

 on Pen-y-gent now cut up, and forming part of the boundary 

 wall of Horton, was not situated exactly on the summit of the 

 fell. The station on Ingleborough could not be satisfactorily 

 identified, but the highest point of the mountain corresponds 

 very nearly with it in its bearing and distance from the old 

 hut, as given in the account of the survey. Assuming as a 

 base for the calculations the distance of the summit of Ingle- 

 borough to that of Pen-y-gent, which we shall call 32, 1 60 feet, 

 the errors of such of the distances as are comparable with those 

 of the Ordnance Survey will be ; 



Ingleborough to the Calf +32 feet. 



Ditto Shunnor Fell . . — 22 



Ditto Whernside . . . + 6 



Shunnor Fell to the Calf +18 



Signals. — Where stones were at hand, small towers five to 

 eight feet high with bases six to nine feet in diameter were 

 erected. When the summit of the hill was destitute of rocks, 

 the (pyramidal) signals w r ere formed of large sods. These 

 signals were invariably placed on the loftiest point of the hill, 

 determined in doubtful cases by resorting to a well-adjusted 

 twelve-inch telescopic level. 



Description of the Theodolite. — With the exception of a few 

 observations made by a common four-inch theodolite, the ho- 

 rizontal angles were measured by a six-inch theodolite, con- 

 structed in the autumn of 1 826, by Mr. P. Lealand, London. 



M 2 The 



