text:  The known laws of matter authorize us to suppose that a body which is constantly giving out so large an amount of heat as the sun is must be progressively cooling and that by the process of cooling it must contract; if therefore we endeavour from the present state of that luminary to infer its state in a time long past we must necessarily suppose that its atmosphere extended much further than at present and we are entitled to suppose that it extended as far as we can trace those effects which it would naturally leave behind it on retiring; and such the planets are