XI. Description of a Barometer, which marks the Rise and Fall of the Mercury from two different Times of Observation

In August last, I read to this Society the Description of an Air Thermometer intended to record the various degrees of heat at every instant; and mentioned my intention of constructing a barometer, which would, in the same manner, record the variations of the weight of the atmosphere: Both which I proposed to adapt to one piece of clock-work. This piece of machinery appearing too complicated and expensive for general use, I contrived a thermometer, which marks the extreme points of heat and cold from any two times of observation. Of which instrument I also lately read an account, and produced the machine itself.