Am is or aren't able written either as you term or two
- Am, is, or tend to be, unable; -- written either as one word or two.
c.1400, from can (v.1) + not. Old English indicated the notion by ne cunnan.
When the stream consists of drops following one another in single file, no such increase of section is possible; and then the constancy of the total stream requires a gradual approximation of the drops, which in the case of a nearly vertical direction of motion cannot stop short of actual contact.