Eugène-Antoine Demarçay was a French chemist born on March 4, 1852. He is best known for his work in the field of spectroscopy and for discovering the element holmium in 1879. His research contributed significantly to the understanding of rare earth elements and their properties. Demarçay's studies focused on the analysis of lanthanides, a group of 15 chemical elements. He utilized advanced techniques in spectroscopy to identify and isolate these elements, which are important in various applications, including electronics and materials science. His contributions have had a lasting impact on the field of chemistry.