Alexander Adie (1774-1858), invented and patented the sympiesometer in 1818. The patent entitled "An Improvement On the Air Barometer" was developed primarily to replace the marine barometer. The top part of the tube is filled with hydrogene whilst the lower part and the open bulb contains a coloured almond oil. Hydrogen, being affected by both pressure and temperature, makes it necessary to first take a reading from the mercury thermometer using the index finger at the top of the sliding scale and then reading the barometric pressure, ie. the level of the oil, against the lower part of the sliding scale, the figure was then recorded on the dial below.