The Marquise's first scientific work was an investigation regarding the nature of fire. The French Academy of Sciences had offered a prize for the best memoir on the subject. Among the contestants for the coveted honor were the chatelaine of Cirey and the celebrated Swiss mathematician, Leonard Euler. The Marquise was unsuccessful in the contest, but her paper was of such value that the eminent physicist and astronomer, Arago, was able to characterize it as an "elegant piece of work, embracing all the facts relating to the subject then known to science and containing among the experiments suggested one which proved so fecund in the hands of Herschel." In this remarkable _Memoire sur le Feu_, which is printed in the _Collections_ of the Academy, the Marquise anticipates the results of subsequent researches of others by maintaining that both heat and light have the same cause, or, as we should now say, are both modes of motion. The second book written by this remarkable woman is entitled _Institutions de Physique_, and was dedicated to her son, for whose benefit it was primarily written. It deals specially with the philosophy of Leibnitz and discusses such questions as force, time and space. Her views respecting the nature of the force called _vis viva_, which was much discussed in her time, are of particular interest, as they are not only opposed to those which were held by Descartes and Newton, but also because they are in essential accord with those now accepted in the world of science. All things considered, the Marquise du Chatelet deservedly takes high rank in the history of mathematical physics. In this department of science she has had few, if any, superiors among her own sex. And, when we recollect that she labored while the foundations of dynamics were still being laid, we shall more readily appreciate the difficulties she had to contend with and the distinct service which her researches and writings rendered to the cause of natural philosophy among her contemporaries. The first woman to occupy a chair of physics in a university was the famous daughter of Italy, Laura Maria Catarina Bassi. She was born in Bologna in 1711--but five years after the birth of Madame du Chatelet--and from her most tender years she exhibited an exceptional facility for the acquisition of knowledge. After she had, through the assistance of excellent masters, become proficient in French and Latin, she took up the study of logic, metaphysics and natural philosophy. In all these branches of learning her progress was so rapid that it far exceeded the fondest expectations of her parents and teachers. Thanks to a wonderful memory and a highly developed reasoning faculty, she was able, while still a young maiden, to prove herself the possessor of knowledge that is ordinarily obtained only in the maturity of age and after long years of systematic study.