350 Ordnance Survey Astronomical Observations. 



Astronomical Observations made with Airy's Zenith Sector , 

 from 1842 to 1850, in the determination of the Latitudes 

 of various Trigonometrical Stations used in the Ordnance 

 Survey of the British Isles. Edited by Captain Yolland, 

 R.E., under the direction of Lieutenant-Colonel Lewis A. 

 Hall, Royal Engineers, Superintendent of the Ordnance 

 Survey, and published by order of the Master-General 

 and Board of Ordnance. 



This is a ponderous quarto volume containing 52 pages of 

 letterpress, and 1009 pages of figures and numerical results, 

 as a contribution towards an exact knowledge of the latitudes 

 of twenty-six stations on the Ordnance Survey of Great Britain. 

 It will doubtless be very favourably received by the scien- 

 tific public, and is an excellent specimen of the searching 

 manner in, and practical skill with, which this great opera- 

 tion is now being carried on ; while persons in general will 

 see, from the voluminous extent to which the observations 

 and calculations in this one department have neeessarity 

 expanded, — how essential it is that the whole should be 

 conducted by the Imperial Government. 



As the attention of persons in our neighbourhood has lately 

 been attracted almost wholly to questions of the best scale 

 for the maps of the survey, we may as well remind them, that 

 to make a sensibly perfect map of the whole country on any of 

 the scales proposed, two descriptions of operations are neces- 

 sary; one consisting of terrestrial determinations of distances 

 in feet and inches by means of measured base lines and trian- 

 gles : the other, of astronomical observations, in terms of lati- 

 tude and longitude, to fix the part of the globe wherein the 

 surveyed may be situated ;* and to furnish, by being compared 



* It used to be objected against the old one-inch maps of the Ordnance Sur- 

 vey, that however accurately the fields and villages might be laid down there- 

 on, there was nothing to shew in what part of the world the places might be 

 situated ; i. e. f there were no markings of latitude and longitude on the sides 

 of the sheet, as had from the first been introduced in the government maps of 

 France. With their usual readiness to meet all the rational requirements of 



