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CONCENTRATING THE EIRE OF A GROUP OF GUNS, ETC. 
The second variation is when a group consists o£ three guns which, 
are not in one line. If the pivots are not greatly out of line, and 
especially when the arcs of fire are not greater than about 70°, no great 
error will be introduced by considering them as in line, taking d to be 
half the distance between the two outer guns. But if they are much 
out of line, as in figure 3, it is obvious that if the object is at 0, No. 1 
gun requires a greater correction than No. 3; and vice versa if the 
object is at M. 
