J. and G. Rennie

George Rennie was an equally distinguished civil engineer with many academic publications, and was made a Fellow of the Royal Society in 1822.

Both brothers continued their civil and hydraulic engineering interests, with their joint company participating in diverse ways.

[1] In an advert of 1882[2] the company listed the following among their products : More of the products of the Rennie company can be deduced from a catalogue of exhibits from the 1876 exhibition at the South Kensington Museum,[3] which records a number of models exhibited : The brothers' involvement in the support for the screw propeller was significant, as the British Admiralty was reluctant to change away from paddle wheels, believing the pitching of a ship would lift the propeller clear of the water in heavy seas causing the engine stress and rendering the vessel hard to control.

Francis Pettit Smith and Captain John Ericsson had been trying to demonstrate the potential of the propeller for five years, and eventually it was Smith who formed a company to finance the building of the Archimedes (107 ft length) fitted with a Rennie single cylinder engine and 5 ft 9in screw propeller.

[4] This was followed by the Admiralty fitting a 10-foot diameter Smith's propeller to the unfinished sailing sloop Ardent, which was launched in April 1843 renamed HMS Rattler.

[5] The Archimedes was also loaned to Brunel and resulted in him changing the design of the SS Great Britain to screw propulsion, even though the paddle wheels were part constructed, setting back the project by 9 months.