Sunlight deprived of the intensity of its heat was to them one of the essentials of life. Its bactericidal power had been scientifically proved ages before, and a family had been set apart for testing its effects both qualitatively and quantitatively. It was not merely a loose knowledge that they had acquired of the antiseptic influence of sunshine. They had measured exactly its power of depriving microbes of their deadliness in the case of every disease; and they knew to a nicety how strong or weak it would be needed in order to check their ravages in any constitution, whether concentrated on a spot or diluted and spread as in a bath, how long daily its application would be required, and how many days. It was this family that superintended the sunbaths in their halls of medication, and assisted the medical sages in advising as to their use. It was true that daylight, and especially that of a sunny day, swept one third of the noxious life out of all water open to its influence, whilst the rays of the sun bleached most bacteria of their pestiferous tendency. Yet used indiscriminately sunshine became itself unwholesome, because of the other forms of energy besides light that it brought with it from the sun and the intervening spaces. If not used with caution, it would destroy the microscopic allies of human life in the body, rendering feeble the phagocytes that devour the virulent microbes; it would by its great heat injure the delicate tissues of the brain, and by its magnetism and weight press heavily on the nerves and the circulation. It was the duty of the solometric family to rid it of its unwholesome elements, and to indicate the exact amount and use of it that would be beneficial in every state of the body. Another of the duties of this family was to cultivate colonies of microbes of the various diseases and make them harmless by means of sunlight for use in inoculations against their own unmodified bacterial kin. One of their greatest aids in this process was the use of the water of the sea; wherever it did not kill the bacteria completely, it emphasised the bleaching power of sunlight over them and rendered them the allies of the human system in its struggle against all disease and decay. This sterilisation of disease was one of the most important functions of the family. It was they who led the flight-gambols of the Limanorans into the outer fringe of the atmosphere, where they might drink in the elixir of unadulterated sunshine; their guidance and contrivances were needed even there, in order to prevent the action of the other energies in the light growing deleterious. Even moonlight and starshine had their uses in the hands of this skilled family. They could separate the deadly or poisonous elements of moonbeams to help them in destroying bacterial life, and leave only their healthy and inspiring tendencies; thus dealt with, the rays of the moon gave a stimulus to the brain-tissues which worked up imaginative materials.