In such cases the immediate damage done may be slight; but the effects of prolonged action and the summation of numerous attacks at numerous points are often enormotis, certain of these leafdiseases costing millions sterling annually to some planting and agricultural communities.
In this case the work done by the internal forces will be represented by ~fRpqdrpq, when the summation includes every pair of particles, and each integral is to be taken between the proper limits.
Multiplying out the right-hand side and comparing coefficients X1 = (1)x1, X 2 = (2) x2+(12)x1, X3 = (3)x3+(21)x2x1+ (13)x1, X4 = (4) x 4+(31) x 3 x 1+(22) x 2+(212) x2x 1 +(14)x1, Pt P2 P3 P1 P2 P3 Xm=?i(m l m 2 m 3 ...)xmlxm2xm3..., the summation being for all partitions of m.
GP2), (20) provided the summation ~ on the left hand be understood to include each pair of particles once only.
being a separation of (n1 1 n' 2 n3 3 ...) and the summation being in regard to all such separations.