But when I came to research it I found that there was an excellent summary of John's working life in Graces Guide to British Industrial History
John Firth (c 1824-1869) Merchant and steel manufacturer
c.1824 Born son of Thomas Firth, Senior in Sheffield
1841 Living in Sheffield: Thomas Firth (age c52), steel refiner, with Mary (age c48), Mark (age c220 a clerk, Thomas (age c190 a steel refiner, John (age c17) a clerk, Edward (age c11), Mary (age c9), Elizabeth (age c6), and Charles (age c4)
1850 Thomas Firth Snr died. John joined his brothers in their business, Thomas Firth and Sons.
1856 Married Charlotte Harding
1861 A steel and iron manufacturer, living in Chesterfield with Charlotte 31, Charles H Firth 4, Lewis John Firth 2, Mary Alice Firth 10 months
1869 Died at sea, whilst on holiday with his wife in the Mediterranean
Holt House also appears on my website - I spent a couple of years there as a pupil!
As a footnote the arrangements for the funeral was made by Mr Skelton Cole, one of the Cole Brothers