Clippings

While in Berlin, Euler was asked to provide instruction in elementary science to the Princess of Anhalt Dessau. The result was a multi-volume masterpiece of exposition, subsequently published as Letters of Euler on Different Subjects in Natural Philosophy Addressed to a German Princess. This compilation of over 200 “letters” introduced subjects as diverse as light, sound, gravity, logic, language, magnetism, and astronomy. In the course of the work, Euler explained why it is cold atop a high mountain in the tropics, why the moon looks larger when it rises, and why the sky is blue. He ranged further afield when he discussed the origin of evil, the conversion of sinners, and the intriguing topic of “Electrization of Men and Animals.”

Writing about vision in a “letter” dated August 1760, Euler began with these words: “I am now enabled to explain the phenomena of vision, which is undoubtedly one of the greatest operations of nature that the human mind can contemplate.” The poignancy of this remark, coming as it did from a partially — and soon to be totally — blind author, is striking. But Euler was not one to let personal misfortune interfere with his attitude toward the wonders of Nature.

Letters to a German Princess became an international hit. The work was translated into a host of languages across Europe and eventually published (in 1833) in the United States. In the preface of the American edition, the publisher gushed over Euler’s expository skill in guaranteeing that

the delight of the reader is, at every step, commensurate with her improvement, and each succeeding acquisition of knowledge becomes a source of still increasing gratification.

In the end, this was Euler’s most widely read book. It is not always the case that a scholar working at the very frontier of research can step back to write a treatise accessible to the layman, but this Euler surely did. Letters to a German Princess remains to this day one of history’s finest examples of popular science.