empty; they are filled with a wonderful substance, unlike any of the forms of matter which we can weigh and measure. A cosmic jelly almost infinitely hard and elastic, it offers at the same time no appreciable resistance to the movements of the heavenly bodies. It is so sensitive that a shock in any part of it causes a "tremour which is felt on the surface of countless worlds." Radiating in every direction, from millions of centric points, run shivers of undulation manifested in endless metamorphosis as heat, or light, or actinism, as magnetism or electricity. Crossing one another in every imaginable way, as if all space were crowded with a mesh-work of nerve-threads, these motions go on forever in a harmony that nothing disturbs. Thus every part of the universe shares in the life of all the other parts, as when in the solar atmosphere, pulsating at its temperature of a million degrees Fahrenheit, a slight breeze instantly sways the needles in every compass-box on the face of the earth. Still further striking confirmation is found in the marvellous disclosures of spectrum analysis. To whatever part of the heavens we turn the telescope, armed with this new addition to our senses, we find the same chemical elements with which the present century has made us familiar upon the surface of the earth. From the distant worlds of Arcturus and the Pleiades, whence the swift ray of light takes many years to reach us, it brings the story of the hydrogen and oxygen, the vapour of iron or sodium, which set it in motion. Thus in all parts of the universe that have fallen within our ken we find a unity of chemical composition. Nebulæ, stars, and planets are all made of the same materials, and on every side we behold them in different stages of development, worlds in the making: here an irregular nebula such as our solar system once was, there a nebula whose rotation has at length wrought it into spheroidal form; here and there stars of varied colours marking different eras in chemical evolution; now planets still partly incandescent like Saturn and Jupiter, then planets like Mars and the earth, with cool atmospheres and solid continents and vast oceans of water; and lastly such bodies as the moon, vapourless, rigid, and cold in death.