PT RR - Surprise Group * August

 I usually participate in this RR by sending 3 postcards and in return I receive another 3. I only have 2 here, sent by Ana Cláudia and Tiago but Nídia also sent me one, which I already had, the same windmill card that Paulo sent me in June 2019.

Photo by: François Kollar

This is a photo of a miner and his lamp, in a mine in Saint-Etienne, France, in 1931. 

The lamp was not only used for lighting, it was also used to detect the presence of methane which, in contact with oxygen, in closed environments, can form an explosive mixture that detonates easily in the presence of flames or sparks, and constitutes a great danger in coal mining. These safety lamps, in which the flame was protected by a metal screen, served as an indicator of the presence of the explosive mixture, as in this case the flame changed its appearance. The metal screen dissipated the heat of the flame so that the gases outside did not reach the necessary temperature to ignite.

Jaca is a small town in the Spanish province of Huesca and is known as the capital of the Aragonese Pyrenees. It is a tourist center that attracts visitors thanks to its historical heritage, the Camino de Santiago and winter sports.