• Mr. '^ixon on the Heights of the Hills of fVenslei/dale. 431 



boring has been carried 250 feet below the surface, but with 

 occasional changes in the strata. What these were I was unable 

 to learn ; Mr. Merritt, the proprietor, being absent at the time. 

 While the water of the creek, only a few feet off, is quite 

 sweet, that of the spring is very salt, and copious. It is some- 

 times very red. Fifty gallons make a bushel of salt, which is 

 very white, and in small and thin irregular tables ; SGiO bushels 

 are made in a year, worth on the spot about 5501. sterling. 



The Parallel Ridge, a mountain overlooking this flat, is com- 

 posed of the same materials as the chasm of the River Niagara, 

 which have already been declared to be, successively, from be- 

 low, saliferous sandstone, ferriferous sandstone and slate, cal- 

 ciferous slate, and geodiferous limestone rock. I therefore re- 

 fer the reader to my account of that river for any additional 

 particulars respecting these strata that may occur in that 

 ridge. t t r» 



° J. J. BiGSBY. 



LXIV. On the Measurement [by Trigonometry) of the Heights 

 of the piincipal Hills of Wensleydale, Yorkshire. By John 

 Nixon, Esq. 



[Concluded from page 362.] 



COME time previous to the commencement of the survey, 

 ^ the great levels of the horizon-sector had been fitted up 

 with scales divided into equal parts (of about two seconds each), 

 numbered from the end of the scale the nearest to the eye- 

 piece of the telescope progressively to the one next to the ob- 

 ject-glass. 



The zero of each index (carrying the levels) being placed 

 exactly in a line with that of its graduated arch (fixed to the 

 telescope), on which it moves, the following method was adopted 

 in order to ascertain at what two divisions of its scale the bub- 

 ble of each level would remain stationary on reversing the 

 telescope within its Ys. 



The sector, placed in the shade on a perfectly steady sup- 

 port (such as a rock or well-built wall), having acquired the 

 temperature of the ambient air, the inclination of the telescope 

 was varied until the bubble of either level ; for instance, that 

 of the right index, moved to about the middle of its scale. 

 After a lapse of a few minutes, the divisions of the scale coin- 

 cident with the two extremities of the bubble were read off' and 

 registered. In the second place, the telescope was inverted 

 within its Vs, and the corresponding position of the bubble of 

 (lie left-index level (now uppcrmobl) read oil". Lastly, the 



telescope 



