Meanwhile, back in Sunderland, Spookie wanted to know why Puss was time-travelling. He was quite willing to tell her. “It’s no secret any more,” he said. “Not when it’s far into the future as we are now.
“The only way we Egyptians have managed to guess what King Cambyses is scheming to do is to wait for him to do it, and to see if he succeeds, then for me to travel all through time and round again, to report this intelligence to Pharaoh, in good time to stop the Persian king doing it.”
“Now, as you know,” said Puss, “Egypt is guarded by a harsh desert called the Sinai. It’s hard to invade Egypt because you have to get your army across this big dry desert, until you reach an enormous fortress on the border of Egypt called Pelusium. The distance across the Sinai desert to Pelusium is about 500 km. Since a soldier marching in the desert can only manage 25 km a day, it’s going to take him 20 days to cross the desert. Each day he needs about 5 litres of water, but there’s no rivers or lakes on the way… except the Dead Sea. And that’s too salty to drink. So each man is going to have to take with him a hundred litres of water, along with all his other kit, which is just plain silly.
“That’s the reason Egypt hasn’t been invaded until King Cambyses worked out how to do it. We Egyptians all thought he didn’t have a chance of succeeding. But the Arabs, who lie between Persia and Egypt, were not only willing to grant him safe passage across their land, but to sell him camels. Thousands of camels. And to give him some good advice.”
“Well,” said Spookie, “that will probably cut the journey time to 10 or 15 days. But it doesn’t do anything about finding water for the camel riders.”
“That’s what we all thought,” said Puss. “Yet the camels turned out to be King Cambyses’s secret weapon. Not for carrying the soldiers, but to make a pipeline of camel skins to supply the whole army for 20 days as it crosses the desert – on foot.”
“But surely that’s going to need thousands and thousands of camels. How long a pipe can you make out of one camel?”
“A surprisingly long one, as it turns out. Each camel has four legs, each about a metre and a half in length. You cut off a leg, then you cut off the two squdgy toes, take the bone out the middle, squeeze out the meat, stitch all the leg skins together – and you’ve got a pipe. A good watertight one, and a very tough one too, because camel skins are so thick and rough. And of course they have to be watertight.”
“Do you waste the camel’s body?”
“No, not at all. It’s good to have a big bulgy bit to jump on, to pump water along the pipe.”
“Right,” said Spooky, “so each camel gives you 10 m of pipe. But you need a pipe of 500 km. That’s 50,000 camels you have to buy from the Arabs, which is rather a lot. Do the Arabs even have that many camels?”
“No you don’t need that many camels,” said Puss. “Only 1,000 will do. The secret is to build a chain of cisterns right across the desert, 10 km apart. Each cistern needs to be big enough to give the whole army a day’s good drink. 500,000 litres for an army of 100,000 men. The camel pipeline need only stretch from one cistern to the next.”
“Oh I see. You fill the first cistern, then you pump the entire contents of that cistern into the next one, then into the next, all the way to Pelusium (or just before you get to it, so they can’t see what you’re doing). You roll up the pipe and carry it back to the beginning and do it again and again until all 50 cisterns are full. It may take a year, but when it’s finished, then the army can march.”
“Spot-on,” said Puss. “So my mission is to raid the future for ideas on how to stop it all happening.”
“Well, I wish you the very best of luck.”
“I need it. We Time Cats have had to traverse eternity eight times so far, because each time something new has cropped up we hadn’t thought about. But, as we say in Egypt: ninth time lucky.”
…to be continued.