<I>Pilkington in 1789 describes one large stone, "formerly an object of idolatrous worship, four yards high and twelve in circumference, so exactly poised that a child might easily give it a vibratory motion." We are told in all the later guide books that fourteen young men assembled on Whit Monday in 1799 with the intention of moving it still further. All agree that its equilibrium was disturbed and some describe it as now immovable," but this is not the case. Adam’s Gem of the Peak (1851) states that Mr. Thornhill at considerable expense had it replaced. He adds that the necessary apparatus was obtained from Chatsworth. The smaller stone to the north, about 5 feet long, can easily be rocked by one finger. At the west end are seven or eight more stones on top of one another which are said to rock.</I>
Extract from:
http://www.birchovervillage.co.uk/LocalHistory19.htm
which makes very interesting reading, if you are going to Rowtor Rocks.
baz