Born at Falmouth in 1857 to John and Elizabeth, Chalmers became an engine fitter at a foundry in St Erth in 1881. Aged just 27 he sailed to Brazil, accompanied by his new wife Elizabeth, as Superintendent of the famous Morro Velho mine of the St John del Rey Mining Company and immediately set about revolutionising all aspects of its labour and industrial processes. His plans were thwarted by a catastrophic run to surface of the workings in 1886 that closed the mine sending the company into liquidation.
Undaunted, Chalmers proposed radical plans to salvage the company by sinking a new mine in the same lode through vertical shafts at unheard of depths and the installation of a completely new and modern mill. The company was formally reorganised in 1887 and within five years of opening the new mill, gold bullion production had surpassed the record levels of the 1860s and continued to grow.
In 1892 Chalmers negotiated a new contract with the company at wages of £1,200 per annum for the first year, £1500 for the next two years and £1,800 annually thereafter. He was a strict boss, once dismissing a Cornish miner whose marriage to a Catholic woman he refused to acknowledge. He remained in post as Superintendent until his death at Morro Velho in 1924 and was succeeded by his son, Alexander. A plaque dedicated to this talented and singularly minded Cornishman was placed for posterity over the entrance to the main adit in 1901.