In my blog I cover the subjects which I am interested in, since I left work and retired in July 1996 after 40 years as a mining and metallurgy engineer. My purpose is to share these subjects with my family, my friends and those who may find my pages in the Internet through research engines. using keywords Pierre Ratcliffe. All the subjects are closely linked. They correspond to the unfolding of history and to the evolution of knowledge during my lifetime.