77 'i f> Col. rov’s Experiments for 
If the rule deduced from the obfervations on Saleve 
•had been abfolutely free from exceptions, and if there 
had not been particular points in the theory concerning 
which the ingenious author himfelf leems to have enter- 
tained doubts, it would probably have been univerfally 
adopted, without undergoing any very fcrupulous invef- 
tigation ; but the obfervations made at Sun-rifing on Sa- 
leve, gave ref ults that were defective, or lefs than the 
real height. In certain cafes, the equation for high tem- 
peratures, remote from the zero of the fcale, appeared to 
follow a diminiftiing, and in others an increafing pro- 
gfeffion. Hence arofe fome caufes of uncertainty, with 
refpeCt to the fpecific gravities of quickfllver and air, and 
the relative expanfion of one compared with the other; 
efpecially when the atmofphere happened to have more 
or lefs moifture diffolved in it. It was doubtlefs from 
confiderations of this fort, that Mr. de luc, in his book, 
fo ftrongly recommends the making of numerous fets of 
obfervations, in different countries; that, by the united 
labours of all, this interefting part of natural philofophy, 
might be brought ftill nearer to perfection. 
With this general object in view, I am now to give an 
account of the principal barometrical obfervations that 
have been made in Britain, on heights determined geo- 
metrically with great care. Thefe heights are claffed in 
the 
