Albert Einstein (1879-1955).

Autograph letter signed ('A. Einstein') to [Hermann Kobold], [Berlin], 18 July [1914].

In German, half page, 223 x 143mm.

Einstein encloses a 'short reply' (not present) which he asks Kobold to include in the Astronomische Nachrichten (this is Einstein's 'Remarks on P. Harzer's paper: "On the dragging of light in glass and on aberration"', Astr. Nachr. 199 (1914)). He adds a rather acerbic request that Kobold 'ask Mr Harzer to contact any theoretical physicist before he again replies. It is disagreeable to argue over things which have long been clarified'.

Paul Harzer (1857-1932) was Professor of Astronomy at the University of Kiel: in the paper in question, Harzer discusses an experiment performed by Franz Harress in 1909-10 on the passage of light through a rotating polygon of linked glass prisms, and argues that it is at odds with the special theory of relativity. Einstein's response demonstrates at length that 'the experiment together with Harzer's calculation does not deliver a refutation but on the contrary a confirmation of the theory'. Hermann Kobold (1858-1942) was the editor of Astronomische Nachrichten from 1908 to 1938, and was a colleague of Harzer's at the University of Kiel. In spite of Einstein's request, he permitted Harzer a response in the same issue of his journal, which Einstein was obliged to rebut in the following issue.

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