I'm kind of confused as to why `Geometry` is a creatable object and not just an interface definition.  In reality, it looks like the `options` parameter to this function is already a `Geometry` object, because it has the same properties that `Geometry` has and `Geometry` contains no additional information, prototype methods, nor does it copy the inputs.  I have to think about this some more, @shunter might have some ideas as well.