A primer of evolution / by Edward Clodd.

  • Edward Clodd
Date:
1895
Catalogue details

Licence: Public Domain Mark

Credit: A primer of evolution / by Edward Clodd. Source: Wellcome Collection.

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    tion of heat. The ultimate nature of Matter is un- known, but we know something of its structure and properties by learning what it does. It is made up of chemical units or elements, of which about seventy have, to the present time, been discovered. These ele- ments are named atoms (from a Greek word meaning 4 that which cannot be cut ’) because, as yet, they have never been divided. When united together they are called molecules, although even then they are at a certain distance from each other. And those which unite always do so in the same proportions both as to weight and volume. For example, whether we take water from a tumbler or from the ocean, each of the molecules of which it is composed contains sixteen parts by weight of oxygen to two parts by weight of hydrogen. Again, certain atoms unite more readily with certain other atoms. But amidst all changes, they remain unchanged. It signifies not into how many myriad combinations; into how many myriad substances,—animal, plant, or mineral,—the atoms have entered; neither how many millions of years have elapsed to bring about these changes ; the atoms are neither worn nor weakened. In other words, Mat- ter cannot be destroyed. But although Matter takes such infinite variety of form, nearly everything familiar to us,—and the same may apply to things unfamiliar —is made up of only two, or, in a few cases, four ele- ments. For example, oxygen, the most important and abundant of all, and, by itself, both tasteless and invisible, composes nearly one-half of the rocks of the earth’s crust, while every living thing, from a mere
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