JH's attempts with Edward Sabine to measure the difference in longitude between Greenwich and the Paris Observatory. Supplies, for Alexander von Humboldt, JH's measurement of Mount Etna's height. Gives message for François Arago concerning paper on magnetism published by JH and Charles Babbage.

Asks JS to check over and forward to Astronomische Nachrichten JH's paper ['Letter on Fraunhofer's Claims for the Inferiority of Reflecting as Compared to Refracting Telescopes'], which paper calls attentions to errors in the catalogue of double stars published by JS and JH.