In 1894, Henry's three sons, William, James and John, were appointed partners to assist their father and uncle, Henry retiring in 1895. In order to secure increased orders for the firm's staples of rope, cordage, canvas and sail cloth, Henry Birkmyre had invested widely in shipping companies in Glasgow, Scotland, and on the river Tyne in the north-east of England, at the same time promoting the interest of his son-in-law, the shipbuilder William Todd Lithgow. The manufacture of fishing nets also followed as Birkmyre had also invested in a number of steam fishing fleets.
The firm was incorporated as the Gourock Ropeworks Co Ltd in 1903 through the amalgamation of the Gourock Ropeworks Co and New Lanark Mills. New Lanark Mills, New Lanark, South Lanarkshire, Scotland, was founded by David Dale (1739-1806) and Richard Arkwright (1732-1792) in 1784 as a cotton spinning company. It was purchased by the Lanark Twist Co in 1799 with Robert Owen (1771-1858), Dale's son-in-law, as part-proprietor and sole manager. Henry Birkmyre formed a partnership with his brother-in-law Robert Galbraith Somerville in 1881 to purchase New Lanark Mills. Under Birkmyre's supervision, the manufacture of fishing nets from cotton spun at the mills was introduced and skilled operatives and patent net-looms were imported to New Lanark from Refrewshire and elsewhere in Scotland. The manufacture of nets from cotton was a comparatively recent innovation, but Birkmyre clearly sought to exploit markets created through his shipping interests. The partnership was dissolved in 1888 when Birkmyre took over sole proprietorship of the works. A new partnership was formed in 1894 between Henry and his sons William, James and John. With the formation of the Gourock Ropework Co Ltd in 1903, New Lanark Mills became the centre of the company's cloth manufacture.
By 1954 the company had both a large UK and overseas operation. In the UK, as well as the Gourock Ropeworks Co Ltd, there were 4 operating subsidiary companies, namely the Greenock Ropeworks Ltd, Greenock; A Thomson Black & Co Ltd, Shettleston, Glasgow; J Lomax & Sons (Bolton) Ltd, Bolton, England; and the Gourock Ropeworks Co Ltd with sites at Port Glasgow, New Lanark, Govan and Aberdeen. There were also 15 branch offices of the company within the UK. Overseas, the company had subsidiaries operating in South Africa, Canada, Rhodesia (now Zimbabwe), Australia, Argentina and New Zealand, along with offices and agents in most of the former British colonies. The Gourock Ropeworks Co Ltd became part of Bridon Ropes Ltd in 1970 when it was taken over by Bridon Fibres & Plastics Ltd. The works at Port Glasgow closed in 1976. The Gourock Ropeworks Co Ltd still continues to exist but no longer trades.