Extract from Barr's obituary in Nature, 22 August 1931:

"From boyhood he showed inventive talent and all his mind was occupied with the solution of a long series of mechanical problems; while to the development of his patents on a manufacturing scale he applied an integrity that would not brook the least lapse from workmanship of the highest kind."

Barr became the senior partner and the head of the design team at the firm's Glasgow factory, and, in 1912, he resigned his chair to focus on the firm's development. He later developed a number of other instruments including a torpedo depth recorder, rangetaker-tester, aircraft bombsights, and submarine periscopes. The company were from the outset official suppliers to the Royal Navy and many other forces at home and abroad.

Barr never forgot his University of Glasgow connections continually helped to raise large sums to support teaching and research. The University awarded him an honorary degree in 1914 and he was elected FRS in 1923.

The firm that was started by Professors Barr and Stroud became part of the Thales Group in 2001. The firm now employs over 68,000 employees in 50 countries.