224 Proceedings of the Royal Society of Edinburgh. [sess. 
§ 29. It is exceedingly interesting to remark that the deviations, 
of the successive distances from a are alternately positive and 
negative, and that they only become less than one-seventh per 
cent, of a for the distance between A* and A g . Thus, if we agree 
to neglect anything less than one-seventh per cent, in the distance 
between atom and atom, the influential distance from either end 
is 7 a, although the mutual force between atom and atom is null at 
all distances exceeding 2*2 a. 
§ 30. If, instead of /(D) denoting the force between two atoms 
in a rectilinear row, it denotes the mutual force between two 
parallel plane nets in a Bravais homogeneous assemblage of single 
atoms, the work of §§ 27, 28 remains valid; and thus we arrive at 
the very important and interesting conclusion that when there is 
replusion between nearest nets, attraction between next-nearests, 
and no force between next-next-nearests or any farther, the 
disturbance from homogeneousness in the neighbourhood of the 
bounding plane consists in alternate diminutions and augmenta- 
tions of density becoming less and less as we travel inwards, 
but remaining sensible at distances from the boundary amount- 
ing to several times the distance from net to net. 
(. Issued separately June 9 , 1902 .) 
