The planets revolved in circles because it was in their nature to do so, just as laudanum sends to sleep because it possesses a virtus dormitiva. - Agnes Mary Clerke

Comets encountering these precincts must be perplexed to decide between the two potentates claiming their allegiance, and perhaps on occasions pay their court to each in turns, throwing out tails, as they do so, in all sorts of anomalous and contradictory directions.

Is it not reasonable to think that by far the greater part is solid and dark, and that this immense globe is encompassed with a thin covering of that resplendent substance from which the sun would seem to derive the whole of his vivifying heat and energy?

Thus, not merely what it can do, but the rate at which it can do it, has to be considered in estimating the value of photography as an ally in astronomy.