- Tweet volumes in an area can be shown by 3D towers - this helps give a better sense of scale than a flat picture (and I'm normally not a fan of 3D)
- Each language can be hidden or shown using the Google Earth checkboxes that control layer visibility. If you want to focus in on just French or remove all English, just check the appropriate boxes.
A happy side-effect of planting several "towers" representing different languages in the same spot is that Google Earth shows the most dominant language most clearly.
Here's a screenshot:
If you want to explore the data yourself the Google Earth file is here