Hello, Zeal,
What a fine coincidence! Earlier today I learned something new about
each other, and here you've asked a question to which my new knowledge applies.
But first, the instances of
each other in your second and third examples are
reciprocal pronouns. The two words go together as one reciprocal-pronoun unit. I believe that's why you feel them to be as one. I, too, feel them to be as one, though I have never, if memory serves, seen
each other spelled as one word in high-quality published writing.
Each other is not a reciprocal pronoun in your first example. There needs to be a slight pause between
each and
other; otherwise
each other would be understood to apply to
they rather than to
block, which I assume you are using as a noun (blocks of wood, blocks of a town, etc.).
As to why
each other in the second and third sentences are spelled as two words, I learned today that, historically, the preposition in such constructions was placed between the two words. The following passage is from Otto Jespersen's
The Philosophy of Grammar (1924), which I ordered earlier this week and started reading today:
quote:
"The distinction between a formula and a free combination also affects word-order. One example may suffice : so long as some+thing is a free combination of two elements felt as such, another adjective may be inserted in the usual way : some good thing. But as soon as something has become a fixed formula, it is inseparable, and the adjective has to follow : something good. Compare also the difference between the old ' They turned each to other ' and the modern ' they turned to each other '".
-- Jespersen, Otto. The Philosophy of Grammar. Henry Holt and Company: New York, 1924.
Historically, then, your second example might have read as follows. I'm not sure whether a comma would have been added or not:
- They looked each at (the) other.
- They looked, each at (the) other.
Perhaps
each other, in its reciprocal pronoun usage, is on its way to being spelled as a single word. If so, I would imagine that text-messaging culture is assisting in that development.
Cheers,
David