" [The Spiral Tunnels] were the largest tunnelling feat undertaken in Canada at the time, and were a remarkable achievement for the days before laser transits and sophisticated surveying techniques. "
The Spiral Tunnels and the Big Hill; Graeme Pole; 1995; Altitude Publishing Canada.
A friend mentioned that some people on the internet had recently contemplated the complexity of the construction work for the Spiral Tunnels. The fact that the tunnels were built with a precise curving route and with a precise gradient - without access to GPS and modern electronic surveying equipment - evokes awe and sparks curiosity to find out what methods were available to the civil engineers and surveyors over a century ago.
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| from: Beautiful BC magazine, summer 1985. |
The headend cars of a passenger train, make their way up the Big Hill in this undated photo.
The photo from the Mount Royal Tunnel book (below) came to mind and I started digging through my textbooks from that era to see if I could connect the activity shown there with some text to explain it.
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from: The Mount Royal Tunnel; Tony & Eric Clegg; 2008; Railfare DC Books.
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I think the spider is in the foreground, putting out its line.
How I came to understand some of this engineering and surveying information ...
If the stars (and sun) are considered to be pinholes in a black ball which encases the earth ... and you can determine 'straight above us' as the position where the sun casts no shadow at 'solar noon' ... then, with accurate chronometers to measure time ... and accurate optical instruments to measure angles ... and math ... you can probably figure out what the inside of the ball should look like at any other time.
Naturally, we have seasons where the sun and black ball appear to shift ... but, trust me, you don't want to read more of my half-baked musings that you have to ...
So, in the olde, olde days, if it was solar noon at the Royal Observatory at Greenwich, England maybe you'd line up a telescope tube with the crosshairs at the sun's centre. Don't try this at home!
Having nailed 'exactly overhead' ... you'd use other telescope tubes with crosshairs ... and a protractor ... to start to work out a list of angles for important stars and the sun at various times of the 24 hour day for 365 days.
... Great! If your watch breaks in Greenwich, you can now use an optical instrument, a table of values and math to figure out what time it is.
MAYBE ... if you want to make a buck ... you can sell a copy of a 'clever but boring math-heavy book of angles and times' to a sailor. First, though, you'd have to calculate and provide many more values for a range of positions across the face of the globe.
Olde Sailor says what? : I, 'Olde Sailor', set my accurate clock at 'noon' when I was last in London towne. Look up yonder ... there are some stars I recognize up above. My chronometer says exactly 6 PM Greenwich time. I'll calculate the 'angles' of those stars. Using the book and some mathematics, I'll calculate where I'd be at "6 PM Greenwich" ... "this star at this angle", "this star at that angle".
Curiosity, commerce and war inspired people, over time, to develop increasingly accurate tables of figures which ... out on the ocean, out in the field, or flying commercial aircraft in the 1950s ... enabled other people possessing accurate optical instruments and chronometers to figure out exactly where they were on the globe.
... And so that's how they built the Spiral Tunnels!
It's not much more complicated than that.
* * *
Think about it ... you're standing at the Big Hill where they want the Spiral Tunnels put.
Your DNA managed to make it across the ocean from Greenwich to Montreal without getting lost and drowning in the dark, wide Atlantic Ocean.
Some explorer/engineer wandered across Canada (maybe even without the help of First Nations guides, for once) and wrote down how to get back from where they had wandered. They produced "a map".
Someone else used that map to decide where to lay down a twin path of metal rails which don't rise more than 2.2 per cent at any point for thousands of miles.
Someone noticed that a United States map showed railways which were pretty close to 'the border' !!
This 'border thing' was somehow hacked out in a line across the wilderness without Global Positioning System satellites.
So someone made the 'business/political decision' to locate this railway line close to the US border.
Working on a limited budget, someone decided that it might be necessarily cost-efficient to run the railway down (up for eastbounds) a suicidal 4.5% grade ... for 23 years and 2 months in all ... until you finish drilling and blasting a couple of nice spirally holes in a couple of mountains.
... And now you stand at 'The Big Hill' in September 1907, as work is set to begin ...
You 'got here by train' but consider all the careful celestial sightings, and angles precisely recorded, and distances accurately measured, and persnickety math done by so many people over so many years to get your Greenwich DNA to precisely this location in the mountains.
* * *
I once asked a kind, patient, unpaid 'career consultant' at Canada Trust which course was superior for my future training needs: the Canadian Securities Institute Professional Financial Planning course, or the more 'famous' course offered by the Canadian Institute of Financial Planning.
I shall always remember the friendly eloquence of his answer as he shook his head, smiled and said:
It's all the same s[tuff] !
* * *
Dear readers, if you can imagine that people used precision optical instruments,
measured angles, recorded distances and specialized powerful math
to get someone's DNA from Greenwich to the Big Hill ...
You will have a 'feel' for the ideas within the textbooks below, because ...
It's all the same s[tuff] !
* * *
In most cases, I'll provide the title page of the textbook first, as there is often interesting information printed there. I did not cut off neighbouring sections or paragraphs in all cases, as I thought you might find them interesting.
A transit is that surveying instrument you are most familiar with.
It measures vertical and horizontal angles.
While it may be perfectly acceptable for a surveyor to put most of their stakes dead-centre where a railway line is to be built on the bald prairie, knowing that the railway will be built right over them ...
When you start at an intensive working like a spiral tunnel, everyone and his horse will be trampling down your carefully-located surveying stakes as they travel to and from the face of the excavation.
So you should survey and precisely mark a set of 'stations' which will not be disturbed ... and then use them to calculate and mark where the advancing tunnel work should take place at regular intervals.
See the illustration for the text above, just below ...
To some extent, this is the principle behind that interesting image from the Mount Royal Tunnel work.
On a map of Montreal Island: 'X' marks the spot of the sod-turning in the City of Montreal ... but one way to be certain that the two working faces of the excavations will meet at the right spot ... is to accurately calculate point-to-point-to-point-to-point... all the way around the mountain. Do this along the sidewalks in the air and light, until you have measured and angle-calculated exactly where the 'Y' ceremonial sod-turning would take place at the planned Town of Mount Royal at the other end of the tunnel.
If you gave someone your traverse details to site 'Y' as they stood at site 'Y' ... and removed any physical clues from the sidewalks etc ... they should be able to measure and angle their way right back to site 'X' where the sod-turning took place.
Once the bores develop into tunnels, the next job would be to maintain their straightness toward each other as the work progressed.
It is hard to imagine how many times experienced engineers and surveyors would check their calculations for a high-profile and expensive project like the Mount Royal Tunnel.
* * *
While tunneling may be a specialized aspect of CPR main line railroading history, it is nothing new for the profession of engineering, particularly if one considers the historical intertwining of coal and rails ...
Coal Mining in Cape Breton
... how many dark holes had been successfully surveyed before the Spiral Tunnels?
* * *
Here is a some elaboration on traverses ...
(see the Mount Royal Tunnel photo)
When you see someone using a transit for surveying ...
you often see another worker holding a stadia rod ...
Easier than shouting:
The transit operator uses hand signals to guide
the positioning of the stadia rod.
As the stadia rod is a standard-sized, precisely-calibrated target ...
it is used for a variety of measuring operations.
How to survey in the dark,
and how to protect your stations from everyone and his horse ...
How to run a traverse for railway tunnels.
Tunnels "often several miles in length ... not uniform in either slope or direction".
* * *
A book which pre-dates the Spiral Tunnels,
which were built from September 1907 to May 1909.
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| from: Yonder Comes the Train; Lance Phillips; 1965; AS Barnes & Co. |
The Tehachapi Loop in 1876.
* * *
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from: Western Rail Trail; Norman McKillop; 1962; Nelson & Sons.
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Above: The view from the Monarch Mine in 1919.
While the Spiral Tunnels always seem to be 'up in the mountains',
as this photo shows well, they were constructed down in the valley.
