Pièce 27 - Letter from John Herschel

8 pp

Feldhausen near Wynberg - The tide observations made at Simon's Bay have suffered a number of difficulties - 'hourly observations could not be carried on through the night - but from 6 AM to 8 PM we have got a complete set' from the 18th to the 30th June. Problem of getting the tide gage observed at table bay - 'nothing but a mass of error and impertinent matter resulted'. Thus [Thomas] Maclear or his observatory assistant personally went every day to observe all the tide observations from that day to the end of June. To get accurate readings you really have to observe the gage for at least an hour. Maclear thus dispatched his only assistant to take lodgings in the town to concentrate solely on taking tide observations. It would be good to erect a self-registering apparatus at Simon's bay. Maclear will apply to the Admiralty for such an apparatus. WW should support his application. JH gives some early conclusions regarding the data from Simon's Bay, and is unsure 'whether the annual part of the solar action as separated from its daily has had much attention bestowed on it'. He gives the following results: A statement of the mean 'mid-water' marks on the Simon's Bay gage in periods, and barometer observations made by Edward Ryan on his voyage from the Cape to Calcutta: A table of interpolated times and heights of tides in Simon's Bay from the hourly observations from June 18 to June 30: A series of observations 'made with no care and with a bad barometer'.