ON THE MOTION OF EOCKETS. Q^ 



S = Hft. 



s n X 

 s =|4ft. \ Sdv^'wcTWU _ 



^= ^ft. / we get __-_^,— ^ 



D = -557 ft. r ^ 



V :=. 1500 ft. V 9-530695 lbs. or gibs. 8|ozs. nearly for 

 X rr 300 ft. ( the weight of charge sought; being 

 w — 42 lbs. \ 3lbs. 9^ ozs. more in this case than when 

 N =r 74- 1 the vessels are ill close action. 



ti —-0012 J 



Hence not only is the destruction of the vessel more cer- 

 tain vrhen the firing commences just as the ships touch each 

 other but a great saving of powder takes place beside, 

 insomuch, that not more than two thirds of the quantity- 

 is expended, that would be required at the distance of 300 

 feet. 



From this circumstance then, and the impossibility of 

 solvin"- the problem rightly from the various causes already 

 enumerated, the effects of which are not reducible to any 

 recnlar laws ; we conclude, that the foregoing table of 

 charges for close fighting is the only one, that can be of 

 the smallest service in practice, and that all attempts at 

 others must be rendered completely futile from the nature 

 and constitution of things. 



II. 



Correction of an Errour in a former Paper on the Motion of 

 Rockets. By W. Moore, Esq, In a Letter from the 

 Author. 



ToMr.NICHOLSOK. 

 SIR, 



A. TAKE the earliest opportunity? of correcting the errour 

 so obligingly mentioned by Zeno in the last number of your 

 Journal: into which 1 inadvertently fell in my paper con- Or. the mo- 

 ^-. i .^ r t 1 1 .. tiun of rockets • 

 cerntng Rockets for .July last. 



Conceive Q R and K w (PI. 8, fig. 2,) erased from the 

 diagram, and QW drawn perp. to Tw produced in the 

 plane T Q W ; also, draw WR perp. to T P and join P W 

 which will be perp. to T W. Then calHng T P unity, TQ 

 will l)e =: f (the same substitution for the several angles 

 remaiuing as befort) ; also sine Z TQ W being expressed 



by :^ by Trig, T W ~ "^-r hence PW = {TP*— T W*)» 



