The story of creation : a plain account of evolution / by Edward Clodd.

  • Edward Clodd
Date:
1893
Catalogue details

Licence: Public Domain Mark

Credit: The story of creation : a plain account of evolution / by Edward Clodd. Source: Wellcome Collection.

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    bined state as mechanical units, are called molecules ; and in their free state, as chemical units, are called atoms. The molecule is a compound body reduced to a limit that cannot be passed without altering its nature ; the atom is a body which has not been yet divided. The atoms, or so-called elementary substances, number, as far as is known at present, about seventy; but many of them are extremely rare, and exist in such minute quantities as to be lamiliar only to the chemist. Although his progress in analysis has not yet given us actual evidence of their compound nature, the evidence thus far gathered points to their common derivation. Eighty years ago, Dalton, working in no luxurious laboratory, but with the meagre apparatus of a few cups, penny ink-bottles, and home-made thermometers and barometers, discovered that atoms combine in definite proportions of weight and volume with other atoms. For example, whether we take water in large or small quantities from the clouds, or from the ocean, or from the fluids of living things, and decompose or break up its molecules, they will always be found to contain sixteen parts by weight of oxygen to two parts by weight of hydrogen ; whether we take salt from the sea or from the blood of animals, its molecules always consist of fixed proportions of chlorine and sodium, thirty-five and a half parts of the one and twenty-three of the other; in each and every case any excess of either element remains uncombined—left out in the cold for want of a partner. Dalton’s discovery changed chemistry from a quali- tative to a quantitative science, giving an impetus to research which at last promises to bring us within sight of the fulfilment of Faraday’s prophecy, that ‘ in the end there will be found one element with two polarities.’ Many workers followed on the lines laid down by Dalton,
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