Straight cistern-tube barometer, 1760-1775.
© Science Museum / Science & Society Picture Library
This barometer was made by Jeremiah Sison of London. It is a standard straight tube instrument of the type common in gentlemen's houses at the time. However, it has two additional features: a vernier scale which gives a reading to 1/200ths of an inch, and an ivory pointer which allows the level of the mercury in the cistern to be taken into account.