Ever Wonder Where The Word "SHIT" Comes From?
Certain types of manure used to be transported (as everything was back then) by ship... Well in dry form it weights a lot less, but once water (at sea) hit it, it not only became heavier, but the process of fermentation began again, which by product is methane gas... As the stuff was stored below decks in bundles you can see what could (and did) happen. Methane gas began to build up below decks and the first time some-one came below at night with a lantern... BOOOOM!
Several ships were destroyed in this manner before discovering what was happening. After that the bundles of manure where always stamped with the term "S.H.I.T" on them, which meant to the sailors to "Ship High In Transit". In other words, 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.
Bet you didn't know that one ;-)