The Age of the Earth |
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a-particles accumulation ACTINIUM amount annual applied Archean assumption autunite average Becker biotite Boltwood calculated calories Cambrian CHAPTER continental shelves cooling Cretaceous density determined diabase disintegration earth earth's crust emanation energy equilibrium estimate evidence evolution existence favour feet figure Geol geological geologists glacial gram of uranium granite half-life period haloes heat helium hypothesis igneous rocks Joly Kelvin land areas latter layers lead limestones limited magma material maximum thickness measurement method million cubic miles million tons nebula number of atoms oceans origin pegmatites Phil planet planetesimals possible pre-Cambrian probably problem production Prof quantity radiation radioactive radioactive elements radioactive minerals radium rate of denudation rate of deposit rays rivers Rutherford sedimentary rocks sediments shale sodium solar Sollas solution solvent denudation sphene square miles Strutt sun's surface temperature gradient thermal thorium tidal tion Uniformitarianism Uraninite velocities zircon دو
Popular passages
Page 78 - After careful reflection on the subject, I affirm that the geological record furnishes a mass of evidence which no arguments drawn from other departments of Nature can explain away, and which, it seems to me, cannot be satisfactorily interpreted save with an allowance of time much beyond the narrow limits which recent physical speculation would concede.
Page 15 - Tait probably overestimated the time when he aftinns that 10,000,000 years is about the utmost that can be allowed, from the physical point of view, for all the changes that have taken place in the earth's surface since vegetable life of the lowest known form was capable of existing there.
Page 14 - ... all geological history showing continuity of life, must be limited within some such period of past time as one hundred million years.
Page 14 - A large proportion of British popular geologists of the present day have been longer contented than other scientific men to look upon the sun as Fontenelle's roses looked upon their gardener. ' Our gardener,' say they, ' must be a very old man ; within the memory of roses he is the same as he has always been : it is impossible he can ever die, or be other than he is.
Page 61 - Now if this be the true reason of the saltness of these lakes, it is not improbable but that the ocean itself is become salt from the same cause, and we are thereby furnished with an argument for estimating the duration of all things, from an observation of the increment of saltness in their waters.
Page 165 - ... gneiss. In this area there is a nearly complete sequence of early palaeozoic rocks. Above these strata there are a few beds of red sandstone of Lower Devonian age. Over these beds and intercalated with them are lava flows ; and, finally, penetrating the whole mass, representing a later phase of this period of igneous activity, are great intrusions of plutonic rocks. Amongst the earliest of the intrusions is a series of thorite-bearing nepheline-syenites. Brogger believes them to be of Middle...
Page 14 - ... ...to deny that the rapidity of the rotation of the earth may be diminishing, that the sun may be waxing dim, or that the earth itself may be cooling. Most of us, I suspect, are Gallios, ' who care for none of these things...
Page 61 - But the vapors thus exhaled are perfectly fresh; so that the saline particles that are brought in by the rivers remain behind, while the fresh evaporates; and hence it is evident that the salt in the lakes will be continually augmented, and the water grow salter and salter...
Page 165 - ... There occurs in the Christiania district of Norway,* a geologically depressed area of nearly 4,000 square miles, which is separated on every side by faults from the surrounding Pre-Cambrian gneiss. In this area there is a nearly complete sequence of early palaeozoic rocks. Above these strata there are a few beds of red sandstone of Lower Devonian age. Over these beds and intercalated with them are lava flows ; and, finally, penetrating the whole mass, representing a later phase of this period...
Page 178 - With the acceptance of a reliable time-scale, geology will have gained an invaluable key to further discovery. In every branch of the science its mission will be to unify and correlate, and with its help a fresh light will be thrown on the more fascinating problems of the Earth and its Past.