HISTORY IS FULL of tasks that have been rendered obsolete by technology, but which were in their day so dominant that they left us dozens of metaphors and maxims still in common use. Most Americans, for instance, ride horses rarely, if at all, but we still rein in, spur on, bridle at, saddle up (we may even hold our horses, or get on our high horse, or lead our metaphorical horse to water in the vain hope that she might drink). Sail power, too, left us with all manner of elegant phrases, which we still use even though few of us really know much about their origins. We might try a different tack, or keel over, or batten down the hatches, or learn the ropes. But it’s the old sailor’s…