A similar microscopic minuteness of division appeared in all their weights and measures. They could weigh in their balances down to the million-millionth part of an ounce. So with their measurement of heat and cold; their thermometers could test ten thousand times the range of temperature that their senses could bear, although their power of endurance of fire and frost was to me something miraculous; their furnaces were able to volatilise the most refractory of metals and earths; they could reproduce the conditions of the most glowing suns, and also the temperature of the coldest interstellar space, which, age by age, they were bringing their frames gradually to bear with the aid of certain foods and combinations of elements. Thus did they hope in some future age to subsist, even when they ventured outside of the atmosphere of the earth. All their measures were based on the decimal system, the fundamental unit for microscopic measurements being the amount of energy in an atom of one of their elements, and that for cosmic measurements the energy that would bring a beam of light from the sun’s surface to the earth’s. They were able to see at a glance the exact amount of energy in any phenomenon, to whatever sense it might appeal, and in their minds there was ever a common measure for all types of force. Their electrometers and magnetometers told not merely the amount of electricity or magnetism in any machine, material, or phenomenon, but the motive-power it would have when applied to any purpose. They could compare at a glance, without any elaborate calculations, the advantages to be obtained from any substance when using it as a force, whether through the electricity or the heat or the gravitational power to be obtained from it. Especially useful was this common measure in dealing with the power of light as separate from that of heat. It was of great importance to them to know the exact amount of energy even in a beam of light which their eyes could not perceive. For they used sunshine as one of their great curative agencies, and the medical families were constantly experimenting on the effect of more or less light upon the microscopic life existing in and around the human body. One of their own new developments had been the consciousness of light all over their skin; they could tell with eyes shut whether it was the light of sun, stars, or moon, or an artificial light which was falling on any part of their body; the effect, even on the mind, differed completely in the four; the sunlight, or at least a certain amount of it, gave exhilaration or even joy; the starshine brought contemplative melancholy; the moonbeam mildly stirred the passions; whilst artificial light varied in its power of exhausting brain and nerve energy with the material or element that produced it.