The Mekarski system was a compressed-air

Pneumatics

Pneumatics is a branch of technology, which deals with the study and application of use of pressurized gas to effect mechanical motion.Pneumatic systems are extensively used in industry, where factories are commonly plumbed with compressed air or compressed inert gases...

 propulsion system for tram

Tram

A tram is a passenger rail vehicle which runs on tracks along public urban streets and also sometimes on separate rights of way. It may also run between cities and/or towns , and/or partially grade separated even in the cities...

s invented by Louis Mékarski

Louis Mékarski

Louis Mékarski was a French engineer and inventor of Polish origin...

 or Louis Mékarsky (the correct spelling is uncertain) in the 1870s. He worked in France

France

The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...

, was born in 1843 in Clermont-Ferrand

Clermont-Ferrand

Clermont-Ferrand is a city and commune of France, in the Auvergne region, with a population of 140,700 . Its metropolitan area had 409,558 inhabitants at the 1999 census. It is the prefecture of the Puy-de-Dôme department...

 (south of France) of Polish origin. Many references to him use the Polish

Polish language

Polish is a language of the Lechitic subgroup of West Slavic languages, used throughout Poland and by Polish minorities in other countries...

 name Ludwik Mękarski.
A problem with compressed-air propulsion is that the air cools as it expands, which can lead to the formation of ice in the power cylinders.