But the Finnish verse is more musical, and it is much more flexible, and the rules of it can be better carried out than in English.

There is much more to be thought about than the placing of four trochaic feet to a line.

Not only must the verse be trochaic, it must also be alliterative, and it must also be, to some extent, rhymed verse--a matter which Longfellow did not take into consideration.

That would have doubled his difficulty.

To make verse trochaic, alliterative and rhymed, is very difficult indeed--that is, to do it well.