Whilst the greatest effort has been made to ensure the quality of this text, due to the historical nature of this content, in some rare cases there may be minor issues with legibility. The nineteenth century was an era Of great prosperity for scientific, inquiry. For numerous phenomena explanations have been found which possess a great degree Of probability. Still it cannot be denied that the present theories penetrate only a little into the real essence Of things, and the investigator Very soon stumbles upon questions whose explanation does not at present even seem to be a possibility. The chemical process that goes on when copper – to retain our former example – is heated in the air is well known. However, the deeper question, why the action takes place just SO and not otherwise, or why the resulting powder is black, still awaits a satisfactory answer.
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