NavList:

Hello,

 I’ve found this Port Chalmers discussion interesting and have come across more information about the design and operation of the Greenwich ball in a presentation “The Ups and Downs of the Greenwich Time Ball” given by Ms Anna Rolls to the Horological Society of New York in 2019, available as a video at the link below.  The presentation is just over an hour long and starts at 7 minutes into the video:  

https://www.youtube.com/watch?v=ubvmCWet6iU

Also I found a paper “The Principal Time Balls of New Zealand” by Mr R. Kinns published in the Journal of Astronomical History and Heritage (2017).  It mentions Port Chalmers and also touches on other practices for checking on time in New Zealand ports, such as attending at the post office to receive a signal (pages 70, 77 of the paper), the use of night signals having coloured lights (pages 89, 90, 91), and time guns (page 91).

There are several references to Mr. Stock, and a letter from him (page 75) gives more mention of (in that case) 9 minutes 17 seconds.

https://adsabs.harvard.edu/pdf/2017JAHH...20...69K

Regards,

Adrian F