simultaneously with a dark ring to Saturn. We might have little difficulty in tracing indications of this concentric structure in the other planets, but we may not linger on this tempting field of speculation.
Having inspected the furnace, which is the grand source of power on the surface of the earth, the inquiry naturally suggests itself: How is this power sustained? How is the furnace kept burning? Formerly, there was a vague idea that the sun could dispense heat for evermore without ever wasting; but the law of the correlation of physical forces tells us, that while the sum of force in the universe is ever the same, any special form of force must waste by exercise unless it is replenished. The sun cannot give forth force without loss, unless it receives in turn. The favourite theory at the present moment is, that the sun is surrounded with a zone of fuel in the form of meteorites, and that it is supplied from this source as the furnace of a locomotive is fed from the tender which follows it. But whence comes this zone? How is the circle of correlation to be completed? Here we have reached the boundaries of knowledge, and even speculation is silent. We can trace only a few links of the chain of causation depending from the throne of the Eternal; the last link is hid in impenetrable mystery. "Lo, these are parts of his ways, but how little a portion is heard of him! but the thunder of his power who can understand?"
