Captain Trouillet in 1885 writes of Chaux-les-Passavant: "The following winter had shown itself unfavorable to the production of ice, the periods of humidity preceding too long ahead the periods of frost. Finally last summer, coming after a wet spring, was exceptionally warm. Such were the circumstances which brought about in the glacière the ruin which could be seen at the end of last October. * * * On the 11th of November, the first effects of frost are felt and the temperature falls in the glacière to -2°: outside the thermometer drops to -3°. On the morning of the 12th, same result, and ice makes its appearance in the grotto, as the report of the observer shows: but the quantity produced is so small that the internal thermometer soon goes above 0°. It is only on the 9th of December that the frost wins definitely; on the 11th, 12th and 13th the chill is intense and reaches -19° outside, stopping at -15° in the glacière. The water coming from the rains between the 5th and the 9th drip at this time through the roof and the big side crevasse: circumstances grow favorable and the ice accumulates. From the 17th, the entrance slope becomes almost impracticable; the icicles grow on the roof, as big as the body of a man. * * * From this time to the end of December, the ice sheet does not increase, for water only arrives by the rare drip of the roof, and only the stalactites increase slowly. Outside, however, the cold continues vigorously, the thermometer on the 31st of December dropping to -15° and to -13° in the glacière. If the production of the ice stops, it is not the cold which is wanting, but the other element, the one which as our former study showed, is the most rarely exact at the meeting. The winter is only favorable on condition that it offers alternating periods of freezing and thawing; so the observer writes in his report: 'it is the water which is wanting, otherwise the glacière would be magnificent.'" Trouillet speaks of the difficulty of winter observations in the following words: "Mons. Briot, the present lessor of the glacière, has the unpaid mission of going every week to the bottom of the grotto to get and put in place the interior thermometer. It is a really hard piece of work at this time of the year: each journey takes about one hour. Besides the chance that a visitor has of receiving on his head one of those magnificent stalactites 1 meter or 2 meters long which fall continually from the roof, it is perfectly disagreeable to him to arrive at the base of the slope otherwise than on the sole of his boots, and to face thus the frequent and painful meeting with rocks whose angular edges dot the surface of the descent, smooth as a mirror set at an angle of 30°."