Busy refers to Great Wheal Busy mine, worked from some time before 1720 until 1909. It first mined copper and later changed to tin. In 1900, a considerable quantity of arsenopyrite was recovered.

In 1775: Smeaton (of Eddystone Lighthouse fame) erected the most powerful engine then built in Cornwall at Wheal Busy;

Great Wheal Busy was the site where in the 1770s James Watt introduced some of his early improvements to the steam engine.

Probably the most dramatic engineering achievement in Cornwall in the 18th century was the Great County Adit. Begun in 1748 by John Williams of Scorrier to drain Poldice. This drainage system was extended to the other mine and by 1778 had been driven through Wheal Busy to North Downs and on into Wheal Peevor. Another branch was cut by 1792 into Wheal Unity and Gorland, and Consolidated and United Mines also discharged their pumped water into the Great County Adit, which eventually extended some 40 miles.

The year 1777 saw the first Watt engine in Cornwall at work; this was at Wheal Busy, otherwise known as Wheal Spirit, Chacewater. The engine for Tingtang mine, near Redruth, had been ordered first, but there was delay in getting the parts to Cornwall and it was not at work until the following year. So the first Watt engine actually erected in that county was the Wheal Busy engine, a 30-inch cylinder.

The cylinders and other castings for both Wheal Busy and Tingtang were ready at Bersham early in May 1777, but when it came to actually shipping them, the Tingtang cylinder was too big to go through the hatches of the boat taking them. So the Wheal Busy engine was dispatched first, much to the annoyance of Watt. The erection of the Wheal Busy engine was entrusted to Thomas Dudley, but Watt himself went down to supervise the completion of the engine. Upon his arrival in Cornwall in August 1777 he found 'Wheal Busy in considerable forwardness', and that 'what ironwork had been made there is little inferior to our own, if any'.

The engine was soon set going, and the reports on the performance were very good. The Wheal Busy engine apparently made "as many converts as a Methodist meeting and inspired them with as great a fever of enthusiasm." Orders for Watts engines soared. In December I778Watt wrote from Redruth to his friend Black: "Our success here has equaled our most sanguine expectations; we have succeeded in saving three-fourths of the fuel over the engines here, which are the best of the old kind in the island."

By 1855 the description of the mine was

" in the parish of Kenwyn, and within the mining district of Chacewater, 4 miles from the town of Truro. The nearest shipping place is at Hayle, 14 from the mine, and the nearest railway station is at Chacewater. The mine is held under a lease for 21 years , from 1855, at a royalty of 1-24th, granted by Viscount FALMOUTH; it is now worked for tin and copper. "

1866 At Wheal Busy there was an outbreak of sabotage against those "adventurers" who were said to be infiltrating the tin industry.

1873 Wheal Busy closed.

In 1907 Wheal Busy re-opened primarily for arsenic production for the Anglo-Belgian Company. The celebrations were such that Lord Falmouth gave a whole bullock to roast for the party. Arsenic was roasted on site until World War II; shortly after this the engine was broken up for scrap

.During the middle of the 1920s Killifreth took over Wheal Busy, mainly to mine arsenic, but this brief revival was over by 1927, and mining there was over.

Remains of calciner, engine houses and smithy can be seen today.