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An Account of a new Method of ILLUMINATING the 

 WIRES, and REGULATING the POSITION ./ 

 the TRANSIT INSTRUMENT. By the Rev. HENRY 

 USSHER, D.D. S.F.T.C.D. M.R.I.A. and F.R.S. 



It is now univerfally allowed that the paffages of the celeftial 

 bodies over the meridian arc more eafily, more * abundantly, and 

 moret accurately taken by means of the tranfit inftrument, than 

 by the method of equal altitudes. 



Every attempt, therefore, to improve this valuable inftrument 

 is of importance -, and as there are fome particulars in the tranfit 

 inftrument of our obfervatory, which appear to me to be advan- 

 tageous improvements, I confider it my duty to lay them before the 



* On account of the uncertainty of weather, which often prevents the cor- 

 refpondent obfervation of altitude. 



t On account of the variation of refraftion at the given altitude, if the ftate 

 of the barometer or thermometer, or both, Ihould be different at the times of the 

 two obfervations. 



Academy : 



