An archaeologist had reached the edge of the Sahara Desert on his way to searching for the lost cities in the desert. Having no way to cross the desert he made his way to the camel stand located nearby. He started talking to the Arab who ran the stand about hiring a camel for the trip.
The Arab asked him, "Will you be needing a seven day camel or a fourteen day camel?"
The archaeologist was new at his job so he had to ask the Arab what the difference was. The man explained that the seven day camel could hold enough water for a seven day trip, while the fourteen day camel could hold enough water for a trip of fourteen days. The archaeologist said he would take the fourteen day camel.
The Arab asked him if he knew how to water his camel. Not wanting to appear inexperienced, the young archaeologist said that he did. So he loaded his gear on the camel, went to the water trough, watered the animal, and started on his way.
On their seventh day on the desert the camel keeled over and died of thirst. Naturally, this made the archaeologist very angry. He double-checked his contract and indeed he had hired a fourteen day camel. He grabbed the saddlebags from the camel and, still fuming with anger, started the long trek back to the camel stand.
When he finally arrived, he started cursing the Arab up and down. The man started shuffling through the contents of the saddle bags.
"Where are the two bricks that were in these bags?" said the Arab.
"What?! I removed them before I started the journey since I saw no reason to carry the extra weight," said the archaeologist.
"I asked you before you started if you knew how to water the camel and you said that you did. Those two bricks are the difference between a seven day camel and a fourteen day camel," said the Arab.
Seeing the obviously nonplussed look on the archaeologist's face, the Arab explained, "When a camel drinks water from the trough, he spreads his legs wide apart so his head can reach the water. In that position, the camel's genitals are exposed. You have to watch him closely and when it has drunk up all the water it can hold for seven days, you must sneak up behind him with a brick in each hand and slam them together on the camel's genitals. When you do that the camel puckers its mouth and goes 'OOOOOOOHHHHH' and sucks up enough water for seven more days."
The stunned archaeologist said, "Damn, doesn't that hurt?"
The Arab answered, "Not if you keep your thumbs out from between the bricks."
