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My Friend was provided with an Inftrument,whofe 
Radius was 38 Inches; and, to avoid all Uncertainty 
in its Motion, it was fixed in an invariable Pofition ; 
and its Field, which took in ten Degrees of Altitude 
was divided by horizontal Threads. The Station my 
Friend chofe was on the Top of Dr. Nisbett’s 
Houfe in Kingftreet near Cheapfide , where he had a 
a fair View of the upper Part of the Building ere&cd 
in the Green Tark. There he obferved that the 
fingle Rockets which rofe the mod erect, were ufually 
elevated at their greateft Height about 6°^. above his 
Level ; and that amongft thefc there were 3 which 
rofe to‘7°i; and that in the daft great Flight of 
Rockets, faid to be of 6000, the Creft of the Arch, 
formed by their general Figure, was elevated about 
From the Care and Dexterity .of my Friend, 
and the Nature of the Inftrument, I doubt not but 
thefe Obfervations are true within a few Minutes. 
The Diftance of this Station from the Building in 
the Green Tark is 4.000 Yards, according to the 
laft great Map of London: And hence it appears, 
that the cuftomary Height, to which the fingle, or ho- 
norary Rockets, as they are ftyled, afeended, was near 
440 Yards: That three of thefe rofe 526 Yards j and 
that the greateft Height of any of thofe fired in the 
grand Girandole was about 61 5 Yards : All reckon’d 
above the Level of the Place of Obfervation, which 
I efteem to be near if Yards higher than the Green 
*Park, and little lefs than if Yards below the Chefts 
whence the great Flight of Rockets was difeharged. 
It Lems then there are Rockets which rife 600 
Yards from the Place whence they are difeharged : 
And this being more than a third Part of a Mile, it 
follows. 
