materiality of air, and the still more recent times when it was found that gases other than air had existence.
Some further speculations, enkindled by the green ray observed in the sunshine, may be here presented as relevant to the subject. Dumas, the eminent French chemist, sought by very careful determination to prove that all atomic weights were exact multiples of that of hydrogen. He found them to be multiples of a number one-fourth that of hydrogen, whence the tenuous masses which lie above the hydrogen on the sun's surface are supposed to be one-fourth the specific gravity of the lightest gas we commonly know. And, as the spectrum it yields is the simplest known or even possible, it is thought that this new unit of the atomic scale may be primal matter, and the source of all material forms. This conjecture is not unsupported by other considerations, for, in the four kinds of stars regarded in the order of their brightness and heat, there is a progressively increasing variety of gases as they approach a lower temperature—a suggestion this as to the origin of our sixty-three so-called elements in chemistry.
In domains above the plane of physics, we can observe many beautiful cases of the law of continuity. On a window-pane in winter we can notice structural forces beginning their work where there has been, as far as we could see, no structure. We may breathe on the glass, and no microscope can there reveal any definite direction in the disposal of the moisture. Yet, from it a symmetrical architecture of frost slowly arises. We may take a crystal just deposited from a solution, break off a corner from it, and replace it in the liquid whence it came, when the damage will be accurately repaired.
Between the inorganic and the organic kingdoms of Nature the old partition-walls have at many points been removed. Formic acid, such as ants secrete, has been made artificially by the synthesis of its elements; and so have other products, formerly regarded as purely organic. Prof. Huxley maintains the opinion that, in the past, highly-complex chemical compounds have passed into the state of what he calls protoplasm, the simplest basis of organic life. The controversy about spontaneous generation is not whether the organic is contained and potential in the inorganic, but whether the transition can be artificially effected now.
Plants, like the fly-catcher, which closes on venturesome insects and absorbs their juices, show us how powers, commonly supposed to be exclusively animal, may be shared by members of the vegetable world. The sensitive-plant has something very like the nervous system which marks the highest types of life, for it not only shrinks when rudely touched, but also when exposed to fumes of chloroform. In the same direction points what in plants generally seems to parallel instinct in animals. If a layer of soil near the surface of the ground be unusually rich and moist, the rootlets in growth are spread almost wholly along that layer, while in any other case they descend.