PHILOSOPHICAL 
TRANSACTIONS. 
I. Description of a Percussion Shell, to he fired horizontally from 
a common gun. By Lieutenant Colonel Miller, late of the 
Rifle Brigade, and now unattached. Communicated by R. I. 
Murchison, Esq. F. R. S. 
Read November 16 and 23, 1826. 
JSefore proceeding to describe this shell, it may be neces- 
sary to say a few words on the theory of rifles, with which 
its construction is intimately connected. 
It is a principle now universally admitted, that the irregu- 
larity in the flight of shot arises from the inequality in the 
specific gravities of their sides, and the action of the air upon 
the inequalities of their surfaces. These imperfections it is 
impossible to guard against in casting; for although the 
mould may be constructed with mathematical exactness, yet 
the metal which is poured into it is known to occupy a larger 
space when hot than when cold, and is found by experience 
generally to contract unequally, as the process of cooling 
proceeds. The same mould will accordingly be found to 
cast shot of different sizes, and hardly ever a perfect sphere. 
MDCCCXXVII, 
B 
