Thanks to a tip-off from a fellow Thamesite, I chanced by an article and sketch of Mr Severn. We can but assume its authenticity, but will endeavour to find the article in its full source to seek verification. The factual data written on the page all appears genuine..so for now lets enjoy seeing a sketch of Mr Severn of the Thames Goldfields.
Source: The Graphic, March 20 1875 page 273
The accompanying paragraph reads:
Preparing for the Transit of Venus, December, 1874
Our illustration is taken from a photograph just received from Mr Henry A Severn, of Grahamstown, Thames, New Zealand. This gentleman, formerly in the Sydney Mint, has, like many other observers, been occupied for some time past in making elaborate preparations for observing the transit of Venus on December 9, 1874. Mr Severn's was the chief of the substations under Major Palmer. The telegraph wires shown in the picture were conveyed a distance of 300 miles to the substation and telescope - an instrument constructed by Mr Severn himself. The Governor, Sir James Fergusson, very kindly sent Mr Severn a fine chronometer, and he got two others all ticking in electric contact with Major Palmer's clock at Christchurch. Mr Severn's very complete and skilful arrangements were unfortunately defeated by cloudy weather occurring at the time of the transit. Our readers will probably find it easier to sympathise with his disappointment than to realise his feelings on seeing the labour and preparation of years thus rendered useless by circumstances far beyond his own control. Well might he exclaim, "L'homme propose - Dieu dispose."