The earliest barometers were called weatherglasses or thunderglasses, because they could predict rain. Filled with water, the water column in the long spout of an otherwise sealed glass bulb, rises in response to low barometric pressure, thus predicting potential rain. The Kew marine barometer was developed following an international conference on meteorology held in Brussels in 1853. It is a cistern-type stick barometer encased in a brass cylinder attached to gimballed brackets for mounting to ship cabin walls or posts. The wheel barometer has a long history but became popular in the mid-1700s. Mercury in a ‘U shaped glass tube of a wheel barometer, reacting to atmospheric pressure, moves a silk string looped to a pulley wheel that adjusts the indicator needle on a graduated dial. The wheel barometer became widely popular in the domestic market and was often artistically designed with ornately carved frames and ivory and mother-of-pearl inlay. Barographs and thermographs work on the principle of expansion or contraction of a coil, chamber, spring or wire in response to changes in barometric pressure and temperature, respectively. An arm with a pen attached records continual change on graph paper. Cloud cover and morphology are studied with instruments like the nephelescope, invented in 1835, and the cloud chamber, invented in 1895.