in the dark garden
a distant lightning flash--
the track of a snail

I see the poem a bit differently. It may be set in night, but I prefer interpreting it to be set in day, day darkened by stormclouds. No mystery. In any case, the key to its best meaning, I feel sure, is the juxtaphor electrical energy's track across the sky forms for the snail's trail, and vice versa--which, for me, makes the snail's track the lightning's track in slow motion--a record on dirt rather than on sky, I might add. Both the electricity and the snail are, or have been, destinationed. But the poem is also a vividly captured moment, as Ross suggests--a moment with briefly transient grandeur and (comparatively) prolongedly transient ungrandeur (which may be the truer grandeur of the two in the long run, unless we perceive the lightning as a reminder of the ultimate cause of all that the snail's journey represents).

Aside: my great vow to start an Important Project, as reported here sometime last week, I think, came to naught. But today, subbing again for the first time in around two weeks, I have a minor idea that may get me back into a play I lost to a computer crash after 4,000 words or so, and thought had commercial possibilities--and ought to be fun to write.) So, maybe a new project. I don't think I'll vow to work on it till finished, though.