so 



PHILOSOPHICAL TRANSACTIONS. 



[anno 1766, 



Hence the true or ultimate length of the base, reduced to the level 

 of the sea, and making a portion of the mean circumference of the 

 earth, becomes 27404.7219 



XXF. Abstract of a Register of the Barometer, Thermometer, and Rain, at 

 Lyndon, in Rutland, 1784. By Thomas Barker, Esq. Also of the Rain at 

 South Lambeth, Surrey; and at Selbourn and Fyfeld, Hampshire, p. 481. 



END OP VOL. SEVENTY-FIVE OP THE ORIGINAL. 



/. Observations on the Graduation of Astronomical Instruments; with an Expla- 

 nation of the Method invented by the late Mr. Henry Hindley, of York, Clock- 

 maker, to divide Circles into any given Number of Parts. By Mr. John 

 Smeaton, F.R,S. Anno 1786, FoL LXXFL p. 1. 



Perhaps no part of the science of mechanics has been cultivated by the inge- 

 nious with more assiduity, or more deservedly so, than the art of dividing circles 

 for the purpose of astronomy and navigation. It is said, that Tycho Brahe and 

 Hevelius laboured this part of their instruments with their own hands. Dr. 



