In the original (1861) article (big red link halfway down that page), Figure 2 (the tower reaching above the surface) is described primarily as a ventilator to

In the original (1861) article (big red link halfway down that page), Figure 2 (the tower reaching above the surface) is described primarily as a ventilator to draw away “smoke and foul air”. He had thought about it. Atmospheric/pneumatic railways were still a popular idea in the mid 19th century. The Dalkey and Paris – St Germain atmospheric railways had each had over a decade of service before closure in the 20 years before Chalmers’ patent. They obviously had their own, considerable issues, but would have reduced the ventilation requirement.