Science.

Waikato Times, Volume XIX, Issue 1580, 19 August 1882, Page 6

Science.

DENSITY OF THE EARTH. Geologists and astronomers have been led, as the result of a more careful and critical examination of the question, to doubt the hypothesis that the earth consists of a great fluid mass surrounded by a comparatively thin shell of solid materials. The general Btability of the earth's crust seems to them to be irreconcilable with the suppoeitioon that, at no great depth from the surface, the whole mass of the globe is in a liquid condition. And if, as against this objection, it be supposed that the solid crust of the globe is several hundreds of miles in thickness, it is difficult, Professor Judd argues, to understand how the local centres of volcanic activity could be'supplied from such deep- seated sources. Then again, if all igneous products were derived from one central reservior, we might fairly expect to find a much greater uniformity of character among those products than really exists. In some cases, indeed, materials of a totally different composition are ejected at the same time from closely adjoining volcanic districts. " Whatever," he goes on to say," may bo the cause of volcanic action, it seems clear that it does not originate in a uniform mass of liquefied material situated at no great depth from the earth's surface." It is now very generally admitted that if the earth were not a rigid mass, its behaviour under the attractive influences of the surrounding members of the solar system would be very different from what is found to be the case, and the necessary rigidity would not be obtained were the greater mass of the earth fluid. " — Chambers' Journal.