Rudolf Clausius Eduard Hagenbach-Bischoff Wilhelm Heinrich Heintz Hermann Helmholtz Gustav Karsten Alexander Mitscherlich Arthur von Oettingen Georg Hermann Quincke Edward Schunck Heinrich Gustav Magnus (German pronunciation: [ˈhaɪnʁɪç ˈɡʊsta(ː)f ˈma(ː)ɡnʊs];[1][2] 2 May 1802 – 4 April 1870) was a German experimental scientist.

His lucid style and the perfection of his experimental demonstrations drew to his lectures a crowd of enthusiastic scholars, on whom he impressed the importance of applied science; and he further found time to hold weekly colloquies on physical questions at his house with a small circle of young students.

This was as a result of his inherited money, his focus on experiment in chemistry and physics, his knowledge of the state-of-the-art methods, the scarcity of other laboratories in Europe at the time, and finally the high value he placed on facilitating the researches of up-and-coming young scientists.

Well-known names in the history of physics who were beneficiaries of Magnus's laboratory in the 1840s include Rudolf Clausius, Hermann Helmholtz and Gustav Wiedemann.

From 1861, he devoted much attention to the question of diathermancy in gases and vapours, especially to the behaviour in this respect of dry and moist air, and to the thermal effects produced by the condensation of moisture on solid surfaces.

His great reputation led to his being entrusted by the government with several missions; e.g. in 1865 he represented Prussia in the conference called at Frankfurt am Main to introduce a uniform metric system of weights and measures into Germany.