In 1972 Canadian scientists R.W. Sheldon and S.R. Kerr set out to reason out the number of monsters that occupy Loch Ness. Because the creatures are reportedly large and rarely seen, it follows that their numbers must be small. (“It has been suggested from time to time that as the monsters are never caught it must therefore follow that they do not exist. This is both irresponsible and illogical.”) By estimating the fish stock available in the loch, they determined that the total mass of monsters is between 3,135 and 15,675 kg. Taking the minimum monster size as 100 kg...