A barograph is an aneroid barometer which has been designed to continuously record measurements of atmospheric or barometric pressure. They were invented in France in the 1840’s and were produced in large quantities in the later part of the nineteenth and early twentieth centuries.
The most common use of aneroid barometer was as a recording device by meteorologists. Detailed records of the weather conditions have been kept across the world, in some cases for several hundred years, and the aneroid barograph allowed at least one of these measurements to be automated. Over time these recording of meteorlogical activity have built up to form a huge library of data, allowing trends in weather activity to be studied and conclusions drawn about the nature of climate change at both a local and global level.
The barograph can also be used as a tool for weather prediction. A barometer indicates the current atmospheric pressure, which has a value in itself, but what’s more relevant is understanding the way in which pressure is changing. The barograph supplies this in the form of the continuous line, or barogram, drawn out over time. A rapid change in the air pressure is usually accompanied by higher winds; falling pressure indicates cloudier weather with a higher chance of precipitation, while rising pressure suggests period of clearer, drier weather is on the way.
See also how barometer works.
Most barographs are designed to record changes in barometric pressure over the period of one week, although some are designed for shorter or longer periods.
Barographs were particularly important at sea, where changes in air pressure indicate future sailing conditions and help sailors to plan their actions. Maritime barographs are often more precise than those used on land because of the importance that changing condition can have on shipping activities.
Another use of this form of barometer was to create flight records for gliders, or sailplanes as they are sometimes known. The aneroid barometer responds predictably to altitude changes and the Federation Aeronautique Internationale (FIA) insisted that they were used to capture data during record attempts and other specific activities involving gliders.
Today the aneroid barometer is being superseded by digital devices for recording atmospheric pressure. However, because many of these devices were built by craftsmen from wood, glass and brass they make attractive objects in their own right and are becoming collectors items. A traditional barograph in its glass case, quietly tracing out imperceptible changes in the pressure of the air, adds an air of scientific enquiry and timeless elegance to any room.
