128 Wln'throp's Barometrical Ohsei 



to a mean height of the mercury in the tube, from which 

 all the variations are measured ; in this, the various height 

 of the mercury is accurately measured from, the surface of it 



the cup. The 



oj from this 



o 



triflln^f?; and always diminishes, as the area of the cup in- 



, in proportion to that of the bore of the tube. That 

 ery one may be able to ascertain the differences for himself, 

 3 diameters of the cup and tube shall now be exhibited. 

 Diameter of the cup in inches and decimals 2. 5. 



Diameter of the whole tube 

 Bore of the tube 



0.45 

 0. 3. 



The observations were made only in the finest weather, 

 when there was very little wind. The mean beiglit of the 

 barometer at Cambridge, in similar weather, is 29. 95. 



August 1st, 1786, at half past nine in the forenoon, at 

 Wcathersfield in the state of Vermont, and at the high wa- 

 ter mark of Connecticut river, the barometer stood at 29. 65. 

 We immediately sat out for the top of Ascutncy, a very 

 high hill in that neighbourhood. Our horses were left three 

 miles from the top. At one o'clock, after a fati^^uin^ walk 



of three hours, we were on the summit of the hill. Barom- 

 eter 27. T. • 



r 



August 5th, 1786, at Williamston, in Yermont, a quar- 

 ter after nine in the morning, barometer 28. 1. This town 

 is situated on the height of land between th^ Connecticut 

 river and lake Champlain ; about forty five miles from the 

 former, and fifty from the latter. The ascent in general, 



O 



easy on both sides. The place of observation was about 



fifty 



