Arduino - Gravity Shield - Analog expansion - i2C?

Hi there,

I wish to create a project with 10x rotary encoders and 10x slider encoders.

As these are analog inputs I would need 20x analog inputs to be able to read this data with an arduino?

What do I need to expand and be able to use 20x (or ever more) analog inputs?

Would there be an i2C module to help expand this?

Many thanks for any support!

Stuart