meafunng Heights zvitb the Barometer . 765 
The Peak of Teneriffe, ./Etna, the mountains of Au- 
vergne and Rouffillon, as well as Hecla in Iceland, are all 
very proper for obfervations in intermediate latitudes. 
Within the ifland of Great Britain, Ben Nevis feems 
to be the belt mountain for barometrical obfervations,, 
becaufe of its great height, its vicinity to the fea, and 
that there is very good ground clofe to its foot (which is 
rarely the cafe in the Highlands) for the meafurement 
of the bale, that would be made ufe of in the geometrical 
operations. 
One of the chief caufes of error in barometrical com- 
putations, I apprehend, proceeds from the mode (though 
limplicity is in its favour) of eftirnating the temperature 
of the column of air from that of its extremities, which 
mull be faulty (m> in proportion as the height and dif- 
ference of temperature are great. Where very accurate 
conclufions are expedited, fimultaneous obfervations, at 
different times of the day, and different feafons of the 
year, fhould be made with feveral barometers, placed at 
different heights, each accompanied with a thermometer 
and manometer. By this method, the progreffion of 
temperature, as well as the law of diminution of the 
equation, from the pofition of the inferior barometer 
above the fea (if fitch diminution doth really take place) 
(u) This is taken notice of by Mr. de luc. 
would 
