funny how stuff gets its name
You learn something everyday...here's your lesson:

Manure: In the 16th and 17th centuries, everything had to be transported by ship and it was also before commercial fertilizer's invention, so large shipments of manure were common.

It was shipped dry, because in dry form it weighed a lot less than when wet, but once water (at sea) hit it, it not only became heavier, but the process of fermentation began again, of which a byproduct is methane gas. As the stuff was stored below decks in bundles you can see what could (and did) happen.

Methane began to build up below decks and the first time someone came below at night with a lantern, BOOOOM!

Several ships were destroyed in this manner before it was determined just what was happening.
After that, the bundles of manure were always stamped with the term 'Ship High In Transit' on them, which meant for the sailors to stow it high enough off the lower decks so that any water that came into the hold would not touch this volatile cargo and start the production of methane.

Thus evolved the term ' S.H.I.T ' which has come down through the centuries and is in use to this very day.

So where were the fans on these sailing ships that lead to the phrase "when the s.h.i.t hits the fan"

I think Groovy's pulling the p*** here

Surely in those centuries everyone had only a tiny strip of land to farm, and therefore home grown manure occurred in adequate amounts and imports weren't necessary?

I'm an expert on feudalism, me

Shipments of manure probably still go on today. The cliffs on the coast of Chile have large accumulations of seabird crap which is rich in all sorts of nutrients. It's harvested and exported as Guano.

You can go into B&Q and buy a bucket of chicken shit for £6. Anyone who can sell chicken shit at £6 a bucket is a marketing genius.

I have no idea wether this is true or not,its a copy n paste of an email i was sent earlier.

Generally speaking, e-mails are complete bollocks.

Sea is salt water obviously and if salt water reached it, it wuld be useless, storing it high would increase its chances of getting wet and would alter the vessels buoyancy as if it got wet as it would increase dramatically in weight.

True

If this rule was not adhered to and the miscreants were discovered then a sign in large red letters was attached to the contraband to act as a warning and prevent selling-on using the acroym ;- "Beware Usage of Low Level - Ship High I Transit"

Gusset.

Bus it.