1900-1901.] Mr Tweedie on the foregoing Paper by Dr Muir. 263 
But Sa^dg ... a,, becomes at the same time r n _fj r - x a . r . 
Hence 
A r = -(-l y, 
and the expansion in question is 
- 3d| + 2aja 3 - 2d 2 d 3 d 4 + . . . . 
Hence, finally, 
N = cq X D(a 2 a 3 . . . a n ) - 2Ja 2 + ^a^dg - . . . 
