This is about Airy's theory of Isostasy. Help me understand it.

He states that density is uniform in Endogenous and Exogenous figures but, their thickness varies. And then we interpret his law with the help of Pascal's law and law of floatation.
But, the confusion I have is
i) even if 9 parts of any feature are submerged in megma and 1 part is visible, how does that accounts for reduced gravitational pull of Himalaya or any other surface feature?

ii) At one place he talks about lighter material beneath the surface and at another, he talks about uniform density?

Question

This is about Airy's theory of Isostasy. Help me understand it.

He states that density is uniform in Endogenous and Exogenous figures but, their thickness varies. And then we interpret his law with the help of Pascal's law and law of floatation.
But, the confusion I have is
i) even if 9 parts of any feature are submerged in megma and 1 part is visible, how does that accounts for reduced gravitational pull of Himalaya or any other surface feature?

ii) At one place he talks about lighter material beneath the surface and at another, he talks about uniform density?