Minimum Science rate? + appaerance of resources

[Rooker]

I'm not sure I've posted in the right forum - but here goes

I was wondering - Is there a minimum number of turns for each advance?

I mean - I can't seem to get mine under 4 turns, no matter how much money I pour into science.

And also - Coal only appears on Jungle or hills, will it still appear on a previous jungle square, if i've terraformed it?

Please help!

 

[Ironikinit]

Four is the minimum.

Coal and rubber will appear in grassland that used to be jungle. It was there all along.

 

[Rooker]

Thanks, Ironikinit.

Doh, have I been wasting a lot of commerce.

Silly me, I've been afraid of clearing jungle before the Steam engine