Can somebody clarify what the two engine houses/site is actually called , I have always thought they were wheal bush, but the plaques refer to wheal unity. A google search brings up pictures under either heading

Same beast. The sign at the bottom of the hill on the Todpool junction says Wh Bush, and as you say, the info board on the the site says Unity Wood.
According to Dines,Unity Wood was also known as West Poldice and as Tolgullow United. I believe it was also referred to as North Wheal Unity, and another amalgamation included it in the St Day United Mines conglomerate.
So take your pick :)

PS. It appears we are close neighbours btw.

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Similar situation to Wheal Clifford then , as clear as mud!
Thanks Roy, Not as active as you on the mining interest scene but I watch the Cornish section with interest

Crikey.

I understand it as the following. (without resorting to old paperwork)

(Bear in mind records run from about 1500 to 1920's and there are many many changes of stuff).

Killfreth Mine worked North Lode which has the engine house with a big stack on it. At the chasewater end of this, a branch goes off which is an extension of Wheal Vor Lode (which was a previous constituent of Chasewater Mine aka Wheal Busy).

Killfreth latterly had 2 other lodes which are in Unity Wood. These are Middle Lode (where Skip shaft and Footway shaft are - bat castles) and South Lode which wasn't developed much. This section was previously known as Wheal Union. South of that is Pits an Vollar Lode (I will ignore Trestrail's Elvan, which is in there as well!). This area was previously known as "Wood Mine" which presumably could be related to Wheal Unity normal mine and Wheal Unity "Wood Mine".

From about 1815ish Unity wood was quite a big copper producer, this was presumably from Trefusis Lode (in the section previously known on old bounds maps from about 1600 as Wheal Bush - [in various south, middle, north guises]. I'm not entirely sure what was going on with William's Shaft (which is in that depression and was previously according to Lean's Engine Reporter a 90") but they then erected (in about 1870) erected Magor's Engine (towards the Wheal Bush section) presumably to develop Trefusis Copper Lode deeper.

Following that (pretty soon) it was known as West Poldice Mine (which I suspect meant that it was largely focussed on the whole Trefusis Lode, right the way through towards Tolgullow.....and then that lot became Tolgullow United.

In that latter period, I think St Day United was an umbrella over those....

Then around 1890ish, you had more focus on Killfreth and the deepening of those lodes which included the ones previously discussed in the N of the woods....these dip towards Hawkes shaft (and are quite flat) so that at depth, Middle Lode was pretty much getting towards the bottom of Hawke's Shaft....

There is a good report on here somewhere by Bawden regarding Killfreth and Unity wood, which is worth a read and largely poaches some of the MRO plans of the place...

What I have yet to find out is why William's Shaft had such a monster engine and Pits an Vollar lode (on which it develops) seems to be of such limited extent (on the plans).....