Thank you all, particularly druxey, I did not find what I am looking for, but the Mechanics Magazines were most interesting - if I could locate some nearer 1878, they might just come up with something. The pumps I am looking for have 3 chambers each - each with one fore and two aft, set side my side, the two aft chambers with pipes down to the Bilges - this would conform with the two cut outs in the deck plating on the Falls of Clyde.
I have recently located a deck plan of the Falls of Garry, showing the layout of just these pumps, which incidentally discharge to the rear, unlike most other bilge pumps that discharge to the side over the pump mens feet. An interesting innovation for the welfare of the pump men for the period - unless of course they were cheaper to install or more efficient. There should be Patent drawings somewhere for this new design, I just need to locate them, and the makers name, then to his catalogue of pumps.