meafuring Heights by the Barometer, 655. 
gentleman hath given us the hiftory of the barometer 
and thermometer, with a very curious and elaborate de- 
tail of many years experiments, made by him, chiefly on 
the mountain Saleve. It would be totally fuperfluous 
here to enter into any circumftantial account of the me- 
thod he makes ufe of, fince that hath already been fo 
fully illuftrated by two Fellows of the Royal Society, 
who have at the fame time given formulae and tables, 
adapted to the meafures of this country, (Phil. Tranf. for 
1774, voL-LXV. N° xx. and xxx.) that nothing farther 
can be defired on that head. 
It may neverthelefs be neceflary juft to call to remem- 
brance that the rule, deduced from the obfervations on 
Saleve, confifts of three parts, ift, The equation for the 
expan lion of the quickfilver in the tube, from the effecft 
of heat, whereby the heights of the columns, in the in- 
ferior and fuperior barometers, are conftantly reduced- 
to what they would have been in the fixed temperature 
of 54°~ of Fahrenheit, independant of the preflure 
they refpeftively fuftained. 2d, When the mean tem- 
perature of the column of air to be meafured, is 69°. 32, 
as indicated by thermometers expofed to the Sun’s rays 
at its extremities; then the difference of the common 
logarithms, of the equated heights of quickfilver in the 
two 
