The changes of temperature must have been as vast as the geological ones. Tropical animals—large elephants, rhinoceroses, hippopotami, etc.—are said by Professor Owen to have inhabited the neighbourhood of Hampstead; and though no evidence remains here of the glacial period, icebergs floated at Finchley, and left their deposits in the shallows of the sea that covered it, and doubtless at that period Hampstead was covered with thick ice. The fossil nautilus, sharks’ teeth, and the plates and spines of echini,[225] have frequently been found, the latter in gravel-pits upon the Heath. Modern geologists have stated that the sand at the top of the Heath is only a small patch, very irregular in shape, and that there was another patch on the top of Highgate; and it is suggested that perhaps these were formerly connected, but that the depression of the ground at Caen Wood may have swept the sand from them. Park, on the other hand, observes ‘that vast quantities of sand exist at Hampstead, the Heath being covered with it at an average to the depth of 10 feet, though in some places it is more than 25 feet in depth, notwithstanding the length of time it has been supplying the Metropolis and intermediate villages.’ Could both be thinking of the same stratum? That the Heath is covered with sandy gravel (in fact, the Heath is confined to the sand) is sufficiently apparent to the ungeological eye, especially in this rugged and denuded portion of it. It has been a vexed question with the artists and the conservators of the Heath whether to fill up these irregularities of the surface or leave them to Nature’s healing. Already, taking advantage of the past year or two’s rest from aggression, she has covered the scarred places with her green mantle, and crowding fronds of common brake have taken to grow on the graves of its old habitat. Great spaces amongst the gravel-pits have been brilliant with the glittering flowers of the common broom, and where the unquenched springs still drain themselves into pools and shallows, stocks of willow-wood have in some instances been driven, which have taken root and put forth branches, and in a few more seasons will be vigorous trees. Our hope is that the present conservators of the Heath, to whom great praise is due for the visible improvement in its appearance, will be patient with this seemingly most hopeless portion of it, and leave the rest to the great Mother’s care. In time the rugged superficies will round and soften, and the hollows be converted into bosky dells, tangles of woodbine, wild-rose, and arching brambles. We have already seen indications of the return of _Erica cinerea_ and _E. tetralix_, once common on the Heath, and the tufted stems and silvery lilac flowers of the indigenous heather.