Dunsthöhle (Vapour Cave) at the Helvetiushügel - an unique natural phenomenon in Northern Europe
The vapour cave is located on the site of a former red sandstone quarry. When the quarry workers reached a certain depth they noticed a “vapour” which caused them to faint. Dead birds and other animals were found again and again inside the pit. When the physician Dr Seip came to Pyrmont in 1712 he investigated these phenomena. He concluded that it was sulfur vapour. Carbon Dioxide was not known then and was only identified as acid air a few decades later. Seip determined in self-experiments by “repeated sweating and inhaling of the sulfur vapour in the pit, that there is nothing at all poisonous therein.” In 1720, with permission from Prince Friedrich Anton Ulrich of Waldeck and Pyrmont, he had a stone vault built above the pit, with a brick lined dome, approximately 6 square feet and 10 feet high, to set up “dry sweat bath” for the spa guests.
Dr Seip had a stone tablet inserted in the dry stone wall that can still be seen today. The inscriptuion reads: “Where you make Italy great with rarities, look here, the sulfur pit evaporates from Pirmont’s bosom”. With this Seip alludes to the Grotta del Cane, or dog cave, near Naples. Seip was the first to discover the healing properties of the carbon dioxide gas. Even though his dry sweat bath couldn’t be used uninterrupted due to the inconcistent carbon dioxide levels, he was able to determine that people from all levels of society “praise a good improvement and help with swollen feet, gout pains, stiff limbs” and relief of other conditions.
Today we know the source of the carbon dioxide. The carbon dioxide gas emanates here in the vapour cave in its dry form. This occurrence is called ‘mofette’. The gas penetrates to the surface through cracks and crevices in the fountain fissure. The strange behaviour of the gas has impressed visitors again and again to this day. It is 1 ½ times heavier than air, therefore it stays at the bottom of the pit and mainly reacts to air temperature and pressure. Within the gas, one experiences the sensation of warmth, although the gas temperature is remarkably colder than the surrounding air temperature in summer (for example: air temp.: +31°C, CO2 gas: +16°C). In winter this is reversed (air temp.: -1.2°C, CO2 gas: +2.1°C). The first measurements were taken by the Pyrmonter physician Dr Heinrich Matthias Marcard (1747 – 1817). He describes the CO2 deposits in the vapor cave and a variety of experiments in great detail, as well as the healing properties of the gas: “When one exposes the lower parts of the body to this vapour, without to breathe therein, one will feel a warmth at the lower limbs, which has an exquisitely stimulating effect on the birth parts, and it is felt mostly by the wenches, beause their type of clothing alllows the vapour to flow freely. If one however concludes from this feeling of warmth that the vapour must indeed be warm, one has been hasty, as one can see from the thermometer, that what one believed to be certain, cannot be true.” This paradox – feeling of warmth, although in summer the gas is colder than the air – explains the effect of stimulated circulation of the CO2 gas.
Johann Wolfgang von Goethe was very impressed by the vapour cave during his spa stay in 1801. in his “annuals” he writes: “The strange vapour cave near the town, where the nitrogen, mixed with water has such a strong healing effect on the human body, but on its own and invisibly, forms such a deadly atmosphere, prompted some experiments that were used for entertainment. After serious testing of the place and the level of that layer of air, I could do the striking and pleasing experiments with safe boldness. The bubbles, happily dancing on the invisible element, the flickering wick of straw, suddenly extinguished and immediately reignited and what ever else there was, caused the astonished pleasure of such persons, who didn’t yet know this phenomenon, and left them in awe, if they hadn’t seen it being performed outside before. When I even filled Pyrmont’s bottles with this mysterious agent, took it home with me and repeated the miracle of the burning wick dying in a seemingly empty glass, my company was wholly satisfied and the doubtful fountain master was convinced and thus prepared to let me take those seemingly empty bottles alongside the full ones to Weimar, where their content showed to still be effective.”
The experiments with the burning candle and the bubbles, which have been performed now for more than 200 years, and other presentations with the CO2 gas, are very popular to this day. However, many spa guests have experienced themselves that it is not just suitable for performances, but a healing gas. As Dr Seip had already recognized, the gas is well suited for therapeutic purposes. This therapy has been reinstated by the spa resort Pyrmont in 1950, with the building of the CO2 gas bath house, Am Hylligen Born, todays “Parkpalais”. The gas baths are now given in the Königin-Luise-Bad. The spa resort Bad Pyrmont offers them for the following conditions: Disorders of peripheral blood circulation, hypertension and coronary insufficiency, allergic diseases (asthma, eczema); poorly healing wounds are fully healed. Guests’ experiences of the vapour cave show the full effectiveness of the healing gas: one visitor explained that he had a rash which didn’t heal despite all kinds of treatments. After about six visits the rash dried up and was hardly noticable anymore at the end of his stay. In 2000 the building above the vapour cave and the guard building were renewed and the park was redesigned, in order to incorporate this natural phenomenon as part of the “water run” into the EXPO Project “Aqua Bad Pyrmont” No visitor should miss out on an opportunity to visit the vapour cave.Opening times and guided tours:April – October: • daily 3.00 – 5.30 pm • Saturday, Sunday and Bank holidays 1.00 – 5.30 pmNovember – March: on request (Tel: +49 5281 151588 or +49 5283 8487)