But combs are built side by side, often simultaneously. They grow downwards together, yet always preserve their right distance apart; so that, when finished, there will be an intervening gangway between the sealed surfaces of about a quarter of an inch, which is just enough to allow the two streams of bees to pass each other, back to back. How are these distances preserved, seeing that the bees at work on the bottom edge of each comb are separated by a space of, perhaps, an inch and a half of empty darkness? A simple experiment will at once give a clue to this. If a hive, in which a swarm has constructed about half its depth of comb, be canted a little sideways, so as to throw the combs out of the perpendicular, and the hive be then left for several days, it will be found on examination that all building, from the moment of disturbance, has followed on the new line of verticality. The combs will all be slightly bent to one side. This means either that the bees have a natural sense of the perpendicular, or that they work by the plumbline, as humanity is constrained to do. The fact seems to be that the hanging cluster of wax-making bees performs the office of a living plummet, and really guides the comb in its downward progress. Yet, do bees always suspend their combs? Do they never construct a waxen storehouse, raising it tier above tier from the floor of the hive, after the system of the more intelligent creature, Man? [Picture: Comb built upwards] The first commentary on this is, that such a departure from their common methods would be no improvement, but a retrograde step. These long comb-walls of the bees have a close analogy to the modern transatlantic sky-scraper building. The trouble with all such buildings is to provide them with sufficient base for their height. If American engineers had at their disposal a material of adequate tensile strength, and there were anything in nature to hang them from, it would be, scientifically, a better plan to suspend these buildings than to erect them, because the house would then naturally tend to keep its verticality, and the base-problem would cease to exist. On the same principle the bees, having at hand a material of almost ideal tensility, and a suitable hanging-beam, wisely suspend their heavily, weighted combs from the roof, instead of erecting them, like certain kinds of ant-structures. But it is undoubtedly long racial experience, and not inability to follow the humanly approved method, that guides them here. Rarely—so rarely that the writer, in the course of many years spent among bees, has seen only a single example of it—bees will build comb _upwards_, if circumstances will allow no other way. And this would seem not only to drive the last coffin-nail for the poor instinct-theory, but to carve its epitaph as well.