| Description | Harrison responds to the two enquiries made by Drygalski. He notes that the observed values for 29 and 30 May 1840 compose almost all the values in the volume 'Observations on days of unusual magnetic disturbance', with 6 additional values from 28 May and no observations for any other days. Details of the methods of observation and measurement are not given in this volume, but are likely to be given elsewhere in another published volume relating to the general series of observations. |