Thus if the plane is normal to Or, the resultant thrust R =f fpdxdy, (r) and the co-ordinates x, y of the C.P. are given by xR = f f xpdxdy, yR = f f ypdxdy.
The components of velocity of the moving origin are denoted by U, V, W, and the components of angular velocity of the frame of reference by P, Q, R; and then if u, v, w denote the components of fluid velocity in space, and u', v', w' the components relative to the axes at a point (x, y, z) fixed to the frame of reference, we have u =U +u' - yR +zQ, v =V +v -zP +xR, w=W +w -xQ +yP.
Pwllheli commands a good view of Merionethshire and of the Snowdon range, with the entire sweep of Cardigan Bay, Carreg yr ymbill (gimlet stone) at the mouth of the harbour, Abersoch and St Tudwal's Islands.
Among his publications were the well-known quarterly magazine Y Traethodydd (" The Essayist"), Gwyddoniadur Cymreig (" Encyclopaedia Cambrensis"), and Dr Silvan Evans's English-Welsh Dictionary (1868), but his greatest achievement in this field was the newspaper Baner Cymru (" The Banner of Wales"), founded in 1857 and amalgamated with Yr Amserau (" The Times") two years later.