With this off my mind, let me return to the tenement sponges, which may be likened to so many independent and flourishing manufactories of ozone. Apart from the odour of brine common to every ocean and the scents of the algae and some of the flowering plants of the sea, which are similar all over the world, a coral reef has a strong and specific effluence. The skeletonless coral (ALCYONARIA) has a sulphurous savour of its own, and the echini and bêche-de-mer are also to be separately distinguished by their fumes. Anemones, great and small, seem to disperse a recognisable scent as from a mild and watery solution of fish and phosphorus. But of all the occupants of the reef none are so powerful or so characteristic in this respect as sponges. Puissant and aggressive, these exhalations are at times so strong as to almost make the eyes water, while exciting vivid reminiscences of old-fashioned matches and chemical experiments. Substantial, wholesome, and clean--though generated by a wet, helpless creature having no personal charms, and which, having passed the phase of life in which it enjoyed the gift of locomotion, has become a plant-like fixture to one spot--the gas mingles with other diffusions of the reef, recalling villanous salt-petre and sheepdips and brimstone and treacle to the stimulation of the mental faculties generally. Invariably an afternoon's exploration of the coral reef is followed by a drowsy evening and a night of exceptionally sweet repose. No ill dreams molest the soothing hours during which the nervous system is burnished and lubricated, and you wake refreshed and invigorated beyond measure. I have endeavoured to account for the undoubted physical replenishment and mental exhilaration largely from the breathing of air saturated with emanations from the coral and sea things generally.