eternity; that the hydrogen atom from all eternity has been a hydrogen atom, and to all eternity a hydrogen atom it will remain; for atoms with their properties are indestructible, and are therefore eternal. What man of science would dare to allege that to-day, knowing that he would be laughed to scorn by all his scientific brethren; who would say that these atoms are eternally of the same nature as they have till now been made out to be? What is science in fact, doing as to the atom? It is finding in what is called the atom a composite body, a compound, not an element. This discovery is chiefly due to the researches of Sir William Crookes, who is guided in his investigations by a deeper philosophy of the universe than is common among scientists. It is gradually finding out that these atoms are things that are built up gradually, and that the qualities of atoms are not fixed, but are properties that change with every difference of conditions. Late investigations have shown that when chemical bodies are submitted to extraordinary conditions of cold--such cold as makes the air into a liquid and solidifies hydrogen and oxygen--they suffer the destruction of their supposedly permanent properties. It is proved that, as these conditions are changed, and as lower and lower ranges of temperature are brought to bear upon these chemical elements, one by one their eternal properties disappear, and they lie there changed in their activities, and lose the characteristic traits which enabled them to be discovered as parts of the moving world. Downward and downward falls the temperature, property after property disappears, until science asks, bewildered, what will happen when we reach the absolute zero, what will then become of the properties of matter, what will remain of the characteristics of the elements? Is there not but one Matter, and are not all chemical elements but modifications, aggregations, of this one ultimate matter? Similarly with Force, modern science has made the magnificent generalisation that all the forces that we know are modifications of one Force, and are identical in their essential nature; that heat, and light, and all the various forces around us, electricity, magnetism and the rest, that all these are but vibrations of varying lengths and activities in a subtle medium, and that they may be transmuted the one into the other. They are not fundamentally different, but are one and the same in their root. But if this be so, if there be but one Matter, if there be but one Force, then science is now tending towards unity; and as that unity is traced or aimed at, science will have to pass out of the grosser realm of dense matter into the realm of forces working in subtle media; and we find this wondrous change that, whereas in old days the existence of force was argued for inductively, by studying the changes in matter, now science is beginning to posit the existence of force and to question