Thursday, 18 April 2013

Hunting Great Theodolites

Ever since I bumped into a Great Theodolite in Cape Town in 1995 I have been transfixed by these massive, beautiful instruments.
 Everest theodolite 1995
From my research I believe there have been six large theodolites. The first two were built by Ramdsen.  The first was bought by the Ordnance Survey of Great Britain and the second, although commissioned by the East India Company, was deemed too pricey and also bought up by the Ordnance Survey. The third was ordered by Switzerland in the late 18th Century but never quite made it there before it was cannibalised (some French/Swiss warfaring got in the way).

The East India Company turned to William Cary and Barrow to make them a theodolite of similar size (late 18th C, early 19th).  In the early 19th Century they ordered another theodolite from Troughton and Simms.  And another theodolite was ordered mid/late through the 19th Century. This last one was made of steel and even heavier than the previous theodolites.  It proved too heavy to be of use to lug up mountains and was eventually sent on permanent loan to the Cape Observatory.

The first theodolite was destroyed during the second world war when the Ordnance Survey HQ was bombed.  The second resides in the Science Museum in London.  The third is no more.  The fourth is in the Survey of India offices in Dehra Dun where it is given pride of place next to the Assistant Surveyor General of India's office.  No idea of the fifth but it may be in Calcutta but I've heard no mention of it so preusme it is no more.  And the sixth is in Cape Town (again below).
08 01 03 The Great Theoolite
So of all the extant great theodolites I've seen them all - the Science Museum in London, Cape Town and, last but not least, the Dehra Dun theodolite.
13 04 03 Dehra Dun Survey of India
13 04 03 Dehra Dun Survey of India
The Harris and Co inscription on the vertial circle is confusing me.   Although the horizontal one is etched with Barrow 1833 which fits in with my research.
13 04 03 Dehra Dun Survey of India
To wind the clock back a tad, Ken and myself have been after this theodolite for a while (or was it just me?).  When we realised that we were within spitting distance of Dehra Dun this spring we invited ourselves to visit the Survey of India offices.  Once we arrived in Dehra Dun you can imagine the excitement (OK, mine) when I realised that our Dehra Dun hotel was under 30m from the entrance to the Survey of India offices.  Ken and I went for an explore.
13 04 03 Dehra Dun Survey of India
And we got more excited as we walked down the road.
13 04 03 Dehra Dun Survey of India
OK, you can call us sad, but I prefer to say 'inspired'.
13 04 03 Dehra Dun Survey of India
And here we are.
13 04 03 Dehra Dun Survey of India
We had tea with the Assistant Surveyor General of India - how humbling is that? - and then the great theodolite photos.  Awesome.

As if that wasn't enough geo excitement in one day, on our way down town that evening to celebrate our 'theodolite bag'  we passed a familiar Ruth sight.
13 04 03 Dehra Dun Indian Hydrograhpic Office
By the time we'd finished the photo shoot we were surrounded by over 15 Indian guys with very quizzical looks on their faces.  You could see the thought bubbles coming out of their head: to summarise I think most of them said "crazy woman".
13 04 03 Dehra Dun Indian Hydrograhpic Office
The next day we were privileged to go to another Survey of India office which included their museum.
13 04 04 Dehra Dun Survey of India
We said hi to Everest on the way in.
13 04 04 Dehra Dun Survey- Everest
We spent over an hour soaked in surveying memorabilia - Everest's telescope, the transit telescope of the Great Arc of India, subtense bar, drawing instruments from Montgomery, surveying subterfuge (prayer beads used to survey in Tibet - pray and survey simulataneously) and the most amazing tidal harmonic calculating machine I've ever seen.  Sadly we couldn't take photos but I was gobsmaked by the surveying gems we found.  Absolutely wonderful stuff in the survey capital of India.

1 comment:

pluday said...

Fascinating information and excellent photographs, thanks for sharing them !

I first heard about the Great Trigonometric Survey of India a couple of years back and have since been fascinated by the subject. I am from the city of Bangalore where the proposal to survey peninsular India was developed and initial survey activities carried out in 1800. I have tried to track down artifacts in the city from then and documented there current state. You can read it all here -

Your photographs of the Great Theodolite (which I think is Col Lambton's and not Everest as you refer to it) are fascinating. With your permission I would like to use them in my slide-set. I use these slides for lectures in I give in Engineering Colleges and talks to general audiences as well.

Thanks again !