William of Conches speaks in general terms of the influence of mountains on climate. We have seen how he recognized the fact that the tops of mountains are colder than the valleys below.[803] In another connection[804] he explained that places cut off from the north winds by mountains have dry, warm conditions and are good for winter residence, though less desirable in summer. The opposite is true of places on the north sides. Similarly, places exposed to the east are warm and damp with a pleasant autumn but bad spring weather, and the converse is true of places with a western exposure. This systematic arrangement is deduced from William’s fundamental and oversymmetrical conception of the various climatic characteristics of the cardinal points of the compass. Gunther of Pairis, in his _Ligurinus_,[805] embellishes a description of the mountain ranges of Italy with an imaginative discourse on how they influence the climate: the Apennines temper the moist, summer heat of the south wind, and the crags of the Alps cut off the cold northerly gales of Boreas and Arctos. Giraldus Cambrensis says[806] that Ireland, like all other mountainous districts, produces an abundance of rain. In the _Itinerarium Kambriae_[807] he explains that the lake of Brecknock (Llangorse) in Wales is encircled north, west, and south by high mountains. The great range of Cader Arthur to the south, by cutting off the rays of the sun, renders the climate in the vicinity of the lake both pleasant and healthy. The valley of Ewyas, completely surrounded by mountains (now the Black Mountains), is constantly the resting place of clouds, strong gales, and rain, which make it, in Giraldus’ opinion, an extremely healthful locality.[808]