AAC Publications - http://publications.americanalpineclub.org

The Accident on the Minarets

Lightning

One phase of this ever-interesting subject to the mountaineer has been taken up by Prof. E. Mathias in a recent issue of La Montagne (March, 1933) in an article on “Les phénomènes de la foudre ascendante et globulaire dans les montagnes et les plateaux élevés.” He accounts for the rarity of this type of lightning at high altitudes by the air pressure and cold.

“The pressure of the air in the mountains is but a fraction of the normal atmospheric pressure. The fulminant material which forms at approximately 2,500° C., where it is a blinding white with a very feeble tension of dissociation f, increases its tension in cooling. It necessarily decomposes when f clearly passes the atmospheric pressure. This dispersal temperature therefore rises rapidly with the altitude. At low altitudes, the temperature can be lowered to about 500° C. where the fulminant material, a body optically black dark red must decompose. When the altitude is sufficiently great so that the temperature does not sink below 1,200° C., the color is yellow, more or less pale; at higher altitudes the color of the fulminant material is practically white. . . . The blue coloration indicates the presence of sulphur.”

We wish that more observations might be made on this subject and would like to see the results of research carried out by our members especially in the western mountains.