have often, indeed, longed to know what must have been the aspect which the heavens presented to that strange creature provided with such a marvellous optical instrument. No doubt his eye was generally employed for a much more practical purpose than that of astronomical contemplation. If, however, an ichthyosaurus ever did spare a glance at the heavens, what would have been the sight that would have met his gaze?
The sun would have shone on his earth as on ours. The luminary was certainly larger then to some trifling extent than it is at present. It was, however, in all probability nearly as bright as it is now, though it is just possible that photometric measurements would have shown it to be not quite so lustrous as the orb we know. For, paradoxical as it may seem, there are grounds for believing that the sun, though on the whole losing heat, may nevertheless be waxing somewhat brighter and hotter, and radiating more fiercely than then. But this is a matter which at present we need not further pursue; suffice it now to say that there is not the least reason to think there could have been any very considerable change in the physical characteristics of the sun, as the ichthyosaurus saw it arid as we see it now.
The moon, too, at that remote epoch must have run through just the same phases as it does at present. No doubt our satellite was somewhat nearer to the earth in those days than it is now. Its orb would, therefore, have seemed larger, and its periodic time would have been somewhat less. New moon must then have succeeded new moon at a somewhat briefer interval than at present. It is quite possible that the lunar craters which are now so completely extinct may not have exhausted
