Professor Thury of Geneva coined the terms "static cave" and "dynamic cave" which have come largely into use since, and which practically correspond to the German terms _eishöhle_ and _windröhre_. I do not think the term "static cave" accurate, and prefer the term "apparently static cave" or "cave without distinct draughts." For although there are many caves where the air seems stagnant at times, and there are no distinct perceptible draughts, still that the air is really stagnant all summer appears to me doubtful, and it seems as if the movements of air were distinctly apparent only in certain caves and not in others. Air which is apparently stagnant is found in both pit and cliff caves mainly in the summer months, but even in these I have noticed several times in summer slight movements of air, especially near the entrance. I could not exactly feel the air moving, but by lighting a cigar the smoke could be seen borne outwards exceedingly slowly. At the entrance of the Kolowratshöhle I think there was a faint outward current when I was there. The day was hot and windless, and as the cold air met the hot outside air it formed a faint cloud or mist at the mouth of the cavern. At Saint-Georges, although the air seemed tranquil, I found that the smoke of my cigar ascended rapidly just below the hole in the roof, showing an ascending air current. In the double cave of Chapuis, I found one cavern filled by a little lake over which there was a draught.[25] [25] See Part IV.: Butler, page 308. From the few winter observations we have, there can be no doubt that in winter the movements of the atmosphere are lively, the break in the air column occurring as soon as the outside temperature is lower than that within, when the outer air immediately begins to sink into the cave.[26] [26] See Part III.: Chaux-les-Passavant, page 203; Saint-Georges, page 220. If I have doubts as to the existence of absolutely static caves, it is different about dynamic caves. When a subterranean hollow goes through rocks, with one opening higher than the other, there will surely be distinct draughts. These dynamic caves exist in many parts of the world under such names as cold current caves or blowing caves or windholes. Sometimes they are fissures in broken limestone. Often they are the cracks between piles of boulders. A cool air generally pours from the lower opening in summer while the cold air pours into it in winter, the draught being then reversed. At the upper opening the operation takes place in the opposite way, the hot air being sucked in in summer, and given out in winter. Sometimes, however, changes take place, according to the differences in the outside temperature, in the direction of the air current in the course of a single day.