Between at least 1881 and 1899, George Cumming & Co. was manufacturing forges, blowers and riveting machines. One of George's sons, David Cumming, manufactured his father's patent portable forge in Chicago; that production was eventually taken over by Furness Brothers Co.

Information Sources

• 1884 Transactions of the California State Agricultural Society lists award-winners at that year's State Fair, including George Cumming & Co., which won "Best portable forges" and "Best hand blowers".
• 1899 Crocker-Langley San Francisco Business Directory: "CUMMING GEORGE & CO. (George, David and Joseph M. Cumming), manufacturers of the Cumming Portable Forge and the Cumming Hand Blowr, hydraulic machinery, etc. ,18 Fell opp. corn. 10th and Market."
• 1890 Langley's San Francisco Directory: CUMMING GEORGE & CO. (George and David Cumming), mechanical engineers and machinists, hydraulic machinery, HAND BLOWERS, PORTABLE FORGES, etc. , 18 Fell opp. cor. 10th and Market". Joseph M. Cumming was a bookkeeper at the California Savings and Loan Society.
• 1902-12-16 San Francisco Call had an obituary for George Cumming: "In this city, December 13, 1902, George Cumming, husband of Marion Bain Cumming, and father of David, George M., Joseph M.. Jean, Marion and Blanche Cumming, a native of Leith, Scotland, aged 78 years."
• 1902-12-20 Mining and Scientific Press. "GEORGE CUMMING, a prominent Pacific Coast inventor and engineer, died at his home in San Francisco, Cal., on the 14th inst., aged 78. In 1852 he was chief engineer of the Pacific mail steamship Panama. When the Risdon Iron Works of San Francisco was founded he was made its foreman, and in succeeding years had much to do in a mechanical way with the mining industry of California. Among other devices, he invented and put in general use a portable steam stamp mill and a portable miner's forge."
• 1903-01-10 The Engineering and Mining Journal. "Mr. George Cumming, one of the pioneer engineers of California, died in San Francisco recently. He has been connected at different times with the Risdon, the Fulton and the Union Iron Works of that city. He was the inventor of a portable stamp mill, and also of a portable miner's forge. He was a designer of hydraulic plants, and his work was closely identified with the mining industry of the Pacific Coast."
• 1912 issue of The Grizzly Bear. "San Franciscan Dies in Chicago—David Cumming, who was born in San Francisco, attended the City College, Lincoln Grammar School and Boys' High School and graduated from the University of California in 1876, died at Chicago, December 21st. He learned his trade at the Risdon Iron Works and with his father's firm, George Cumming & Co., and for many years had been engaged in the manufacture of portable forges in Chicago. A brother, Joseph M. Cumming, assistant to President Moore of the Panama-Pacific International Exposition, survives..."