This suppression of the emanations of the native heat of the earth is not only made by the frost, but likewise by the simple binding of the earth, often occasioned by a less degree of cold than that which is necessary to freeze the surface; there are very few countries where it freezes in the plains beyond the 35th degree latitude, particularly in the northern hemisphere. It appears, therefore, that from the equator, as far as the 35th degree, the emanations of the terrestrial heat having always their free issue, there ought to be in that part little or no difference between winter and summer, since this difference proceeds only from two causes, both too slight to produce any sensible effect. The first cause is the difference of the solar action, but as this action is itself much smaller than that of the terrestrial heat, its difference is too inconsiderable to be regarded as any thing. The second cause is the thickness of the globe, which towards the 35th degree, is near 1/590th part less than at the equator, but even this difference can only produce a very slight effect, since at 35 degrees the relation of the emanations of the terrestrial to the solar heat is in summer from 33 to 1, and in winter from 153 to 1, which gives 186 to 2 or 93 to 1. From hence it can only be owing to the consolidation of the earth occasioned by the cold, or even to the cold produced by the durable rains which fall in these climates, that we can attribute this difference between winter and summer; the binding of the earth by cold suppresses a part of the emanations of the internal heat, and the cold, always renewed by the fall of rain, diminishes its intensity; these two causes, therefore, together produce the difference between winter and summer. After having proved that the heat which comes to us from the sun is greatly inferior to the native heat of our globe; after having explained that, by supposing it only 1/50 part, the refrigeration of the globe to actual temperature cannot be made but in 75,832 years; after having demonstrated that the time of this refrigeration would still be longer, if the heat sent from the sun to the earth were in a greater relation, namely, of 1/25 or 1/10 instead of 1/50, we cannot be blamed for having adopted that proportion which appears the most plausible from physical reasonings, and at the same time the most probable, as it does not extend too far back the time of the commencement of nature, which we have fixed at 37 or 38,000 years, dating it from the first day.