[ 5*3 ] 
a&nefsj for, as they were meafur*d by only one 
Obferver, it is evident, that, if any qf the Rockets 
deviated from the Perpendicular, fo as cither to in- 
cline towards the Place of Obfervation, or to decline 
from it, the Height would be given either greater 
or lels than the Truth j but as the Bafe upon which 
they were mcafur’d was 1 190 Yards, the greateft 
Error that edn aril'e on this Account will be but 
very inconftderable. If we fhould fnppofe there 
might be an Error of 30 or even yo Yards, which 
is very highly improbable, it muft then be allowed, 
that fcveral of thefe Rockets rofe to 1000 Yards, one 
to 1100, and another to 1200 Yards, or double to 
any of thofe fired in the Green ‘Park. 
I have been informed, that the Relation of this 
Affair has appeared fo very extraordinary to fome 
Gentlemen converfant in fuch Matters, that they 
have mention'd it as their Opinion, that there mull 
certainly have been fome Miftake, either in placing 
the Inftrument, taking the Heights, or otherwife. 
In anfwer to which I would obferve, that, in all 
the Experiments mentioned in this Paper, 1 the 
Heights were all taken by the fame Pcrfon, viz. 
Mr. John Canton , and that the laft Trial was made 
in the Pretence of ieveral very worthy Members 
of this Society. That the Inftrument, being firft 
fixed to a proper Angle was not alter'd during the 
whole Time of Trial; and therefore, if there had 
been any Miftake infixing it, that Miftake would 
have varied the Height of all the Rockets as 
much as thofe of Mr. ‘Da Cojias j but it was thofe 
of Mr. DaCojla s only, and that at three different 
Trials, which rofe to fuch extraordinary Heights ; 
i • ' and 
