Note 736 — Chapter VII · THE ATMOSPHERE

Robert Grosseteste believed that if you take into account the theoretical principles of the “pyramids” of rays alone (see above, pp. 163–164), mountain heights should be hotter than valleys because the pyramids striking the crests of mountains are shorter than those striking the floors of valleys (De natura locorum, Baur’s edit., p. 66). In other words, mountain summits theoretically ought to be warmer because they are nearer the sun. In the De natura locorum Robert explains that accidental circumstances frequently cause a reversal of these conditions in such a way that the heights may be dominated by cold. Among these accidental circumstances are the winds and also the fact that peaks rise to the “middle space of the air or of the sphere where there is the greatest cold (medium interstitium aeris vel sphaerae, ubi est maxima frigiditas).”