Col. roy’s Experiments for 
of refults arife, and that things fometimes appear contra- 
dictory, or at leaft prefent themfelves under new forms, 
difficult at firft fight to be accounted for, and therefore 
apt to miflead, till by a farther inveftigation of the mat-! 
ter, the true caufes are difcovered. Even irregularities of 
this fort are worthy of being communicated, that others 
may know what hath happened before, and what, in like 
cafes, they may expert to meet with, in the courfe of 
their future inquiries. Improvements of every kind ad- 
vance by flow degrees ; and it is not until things have 
been viewed in every poffible light, that the errors, 
even of our own experiments, are difcovered, the points 
in queftion ultimately afcertained, and the branch of 
philofophy depending upon them, gradually brought 
nearer to perfection. 
Ever fince the difcovery made by Torricelli, the 
barometer hath been applied, by different perfons, in dif- 
ferent countries, to the meafurement of vertical heights, 
with more or lefs fuccefs, according to the more or lefs 
perfect ftate of the inftruments ufed, and the particular 
modes of calculation adopted, by the obfervers. But of 
all thofe who have hitherto employed themfelves in this 
way, none hath bellowed fo much time and pains, or 
fucceeded fo well, as Mr. de luc, of Geneva, f. r. s. In 
two quarto volumes, publilhed fome years fince, that 
gentleman 
