Nature has her own economies that answer to our own. In the use of means to an end, as in the living world, there must be economy of time, of space, of power; there must be adjustments, compensations, and so on. In the tropics vegetation takes its time. No hurry; the heat does not fail. In the temperate zone there is less time, and the pace of vegetation is faster. In the frigid zone it is faster still, the time is brief; there is no prodigality of leaf and stalk and flower; hurry up is the cry. The stalk is short, the flowering is brief, the goal is the seed which must be matured. In our climate, if a plant gets a later start, or is cut down and compelled to bloom again,--for example, the burdock,--how it hastens, how it pushes out its seed-vessels from the main stalk! The late fall dandelions do not indulge in long stalks; they bloom close to the ground and develop their down-seed balloons or parachutes at once. In the Far North the willow and birch are mere running vines, but they achieve fruit. The economy of living nature is the basis of our economy; we improve upon it, we take a short cut, we save time and save power. We trim our trees, we remove obstructions, we fertilize, we graft, we sow and plant. Nature is prodigal of her spawn and pollen to offset the element of chance that enters into the action of the winds and the waves. The wild creatures have their instinctive economies and ways of getting on in the world. They prepare for the winter; they provide for their young; they practice the arts of concealment; they are wise for their own good; they do not commit suicide. The plants have their economies, and the insects have theirs, but when we talk of the economy of Nature, we are beyond soundings. Nature cannot spend more than she earns; her ledgers always balance; her capital cannot be impaired. There is no waste, in our sense, in the universe. Can you destroy magnetism by pulverizing the magnet? Would electricity be quenched if no storm-cloud ever again appeared in the sky? XIV. THE PERSISTENCE OF ENERGY