The work gives a philosophical and textual analysis of the chemical, geological and other excerpts of Marx, as well as his mathematical manuscripts. The presentation of these questions is preceded by a study of the place of natural science in the philosophical and economic heritage of Marx on the basis of the achievements of modern philosophy, textology and methodology of science. A separate chapter is devoted to the analysis of Engels' works on the philosophical generalization of natural science. Previously unexplored manuscripts of Marx and Engels are introduced into scientific circulation.