264 AUitudes ()f Mountains, 4'c. 



It has been remarked that the German Ocean is about 50 

 feet lo~ii}er tlian the Irish Sea. The difference has been ascei- 

 tained by canals communicating with tlie two seas. Without 

 pretending to disprove the statement, I beg to give the result 

 of a few observations which leave the quantity rather question- 

 able. At Symon Seat rock, the square (or middle) tower of 

 York Minster apjieared under a depression of 38'48". The 

 distance is 173,815 feet E.S.E. Hence its altitude is 264^ feet. 

 Tlie mean of several observations at Rumbles Moor gave the 

 depression at 34'l 1^". The distance being (by the Ordnance 

 Survey) 161,924. feet E. by N., the altitude will be 264^ feet. 

 An extremely careful operation on the Banks of the Ouse de- 

 termined the tower to be 234^ feet above the river at York ; 

 13^ feet above the limit of the spring tides at Naburn locks : we 

 have consequently 1 6^ feet for the ulterior fall to the open sea. 



At Leeds the Aire is 74 feet above the Irish Sea. The fall 

 cf the Aire and Calder navigation to Haddlesey lock at low 

 water spring tides was found to be about 62 feet. In one or 

 more places the fall of the Aire is however very perceptible. 

 In my next I hope to be able to furnish more satisfactory in- 

 formation on this interesting subject. 



The plane of the repeating circle having been injured by an 

 accident, the horizontal angles (upwards of 400 in number) 

 were measured with the four inch theodolite. To correct the 

 eccentricity of the instrument, and to attenuate the errors of 

 division and reading off, the angles were measured on six dif- 

 ferent parts of the graduated circle. When the sum of the 

 three angles differed fi'om 180"^, the correction was not made 

 in equal quantities, but depended upon the magnitude and s/?/e 

 of the angles. The distances from Great Whernside to I. H., 

 to P. G., to P. H., and to R. M., together with the angles, as 

 given in the Ordnance Survey, served to form a number of 

 bases admirably disposed for the survey of the upper part of 

 Wharfdale. 



In the course of the past year neai'ly 400 observations were 

 made with the Englefield portable barometer. I have but little 

 reason to be satisfied with either the consistency of repeated 

 observations, or the result of the comparison of the mean with 

 the altitudes trigonometrically determined. On this subject I 

 may probably hazard a few remarks at some future period. At 

 present I shall merely observe, that the altitudes deduced by 

 barometers of various proportions to the cistern, and con- 

 structed by different artists, are, with very few exceptions, con- 

 siderably in defect. X. X. 



P.S. Could I be informed, through the medium of your ma- 

 gazine, where I should be able to find a list of astronomical 

 refractions for a degree or two bduxi: the horizon ? 



LIX. In- 



