Printed observations and letters concerning various maritime inventions by H.C. Jennings including his insulating compass, half-minute glass and log reel. They include three printed observations on his inventions and seven letters. Jennings appears to have had a bad relationship with the Board of the Admiralty, and is described by them as 'that impudent fellow Jennings' [RGO 14/31: 210-211]. An example of this 'impudence' can be seen in a letter to the Board of Longitude in which Jennings accuses the Board of a lack of common sense [RGO 14/31: 214-214a]. Two of the letters are therefore written on his behalf by Mr Durand, a paymaster who worked with Jennings on his magnetic compass. In the final letter Jennings accuses the Board of prejudice against him and threatens to go to 'a Higher Tribunal' [RGO 14/31: 216-217].
An example of Jennings' Insulating Compass is in the National Maritime Museum, Greenwich.