Monday, June 29, 2009

Signal Tower at Blackhead Point, Hong Kong

Image of Signal Tower, on top of Beacon Hill, from outside our window, here in Hong Kong.Dear Gentle Reader,

The external walls of our apartment are, basically, windows.

This spells good news for potential defenestrators.

It also provides poor Pommes, your Hero, with a view on the world that he can no longer play in.

Depending on how long you have been visiting here, you have seen the title view of this post.

Image of Signal Tower, on top of Beacon Hill, seen from higher up in our building, here in Hong Kong.If I go a bit farther up my building, that view changes.

One day I wondered what this building was.

Being a scribe, I went looking for what other scribes might have written and filed about this place.

It turns out that this is Signal Tower and that the outcropping of rock that it stands upon is called Blackhead Point.

In the heyday of frigates and clippers, in Hong Kong's early mercantile culture and history, Signal Tower was very visible and very important.

And, I discovered, the most important piece of Signal Tower was taken down for its constituent metal sometime after 1933.

Everyday at 1 pm, from 1907 to 1920, and twice a day, at 10 am and at 4 pm, from 1920-1933, a large copper ball, situated upon a tall, vertical rod mounted on the top of the building, was released and plunged down to the top of Signal Tower.

After this operation, the copper ball would be slowly winched back up to its resting place in time for its drop, again, the next day.

What was this big copper ball for?

It was a once-a-day (later a twice-a-day) timepiece that ships in the harbour could see and set their chronometers by.

Why was it there? First, a digression.

Hong Kong Island was won by naval arms. Hong Kong Island was ceded by treaty, in 1841, to Britain from China's Imperial Qing Dynasty Emperor.

Hong Kong not only relied on the British Navy for security and projected naval power, but, Hong Kong was the way station for opium on its way into China, and for goods, such as silver, gold, silk, and teas, on their way to Britain, Europe, and the Americas.

Hong Kong, though an International Free Port, nonetheless had many ways of generating revenue and profits off traders and it depended on international shipping which mean frigates, and, much later, steam vessels. And shipping vessels depend on knowing where they are, and what direction they have to head, to get to their markets to sell their wares.

An image of an old frigate in Hong Kong's Victoria Harbour
Signal Tower might have been the third signal tower in Hong Kong. The Signal Tower near my house replaced a less visible signal tower on the Kowloon waterfront built in front of the Tsim Sha Tsui Police Station by 1884. I don't know when that tower was built, but Kowloon was not ceded to the British until 1860 after China's defeat in the Second Opium War

Signal Tower, on Blackhead Point, used to look like this, and you can clearly see the big copper ball on the roof...

Image of the old Signal Tower, built in 1907 on top of Beacon Hill, in Hong Kong.
So, why was knowing the time important? Why was this Signal Tower, with its time signal, important?

To note location, even today, on a map, people talk about the longitude and latitude of that location.

If you imagine the Earth as being a sphere with the North Pole pointing up, and the South Pole pointing down, then latitude are the horizontal markings that slice the world up.

[So the equator (latitude 0), the Tropic of Cancer (23° 26' 22" north of the Equator), the Tropic of Capricorn (23° 26' 22" south of the Equator), and the Arctic and Antarctic Circles (respectively 66° 33' 39" north and south of the Equator) are all latitude lines.]

For Reference, Hong Kong is just below the Tropic of Cancer.

Latitude (in the Northern hemisphere) was easy to calculate if you could find a star close to the North Pole. (It was also easy to tell if you could see the sun at high noon.)

Polaris, the North Star (the one which the handle of the Big Dipper points to), stays within 1° of the North Pole. So, mariners would use an astrolabe or a quadrant or a sextant or an octant to determine how many degrees the horizon was from Polaris (or, in the day, the sun at meridian height, but there is no need to get too technical here).

The number of degrees that the horizon would be from Polaris indicated to the mariner how many degrees of latitude north of the Equator she and her vessel were.

The difficult measurement for the mariner to make was longitude, which measures how eastward or westward you are on a map.

Longitude lines are the lines that cut the earth into vertical slices; all longitudinal lines cross through both the North and South Pole, so Polaris is not a good reference because they all longitudinal lines intercept it.

To determine longitude, besides a rather tricky and math and algorithm intensive lunar reckoning system, the mariner had to know the time. With the time, and a few simple readings, the mariner could easily work out where she was, and which direction she needed to sail in to get to her destination.

Each ship would have, for safety and redundancy, three ship's clocks to allow the crew (or rather one, designated, privileged Master Mariner) to tell the time and work out how far east, or west, around the globe they were on the travels.

The ship's three clocks were kept in bottles, on gimbals, in the heart of the ship to protect them from the elements and the motion of the sea and the ship.

But, still, the duress of life at sea, and the shocks of repeated hits of waves on the bow and sides of the ship, was rough on timepieces, and chronometers necessary for voyages measured in months needed to be checked for accuracy.

Many coastal cities have daily guns, but light travels faster than sound, and that is why Hong Kong had the big brass ball on Signal Tower at Blackhead Point.

Not so witty or pretty, but I look at this tower everyday, and now I finally know its purpose and import. Which is good enough for me, today.



Teresa said...

Dear Scribe,

So glad you're up and about and writing again. This was a very interesting post.

When I was young I read a book called Carry on, Mr. Bowditch, about navigation and the awful algorithms that were used, and how hard it was for the average sailor to understand because the average sailor was usually illiterate in any language, and the Master Mariners needed to read Newton's Principia in Latin. It's a children's book, but it captures a wealth of information in an engaging story.

Another interesting book about the chronometers used to calculate longitude is called Longitude. It talks about the man who invented the ship's chronometer. An adult book, so no engaging story, but also very interesting. Your post reminded me of these old biblio-friends.

I love your pictures of Hong Kong. They make me want to travel...


Barbara Martin said...

Chris, wonderful post about an interesting landmark and how navigation works.

debra said...

Very interesting post, Chris. Is the tower used for anything today?

Richard Wells said...

Mi amigo, I've been wondering why I haven't seen you at the resident djinn, so I checked your blogroll to discover you "haven't made the switch to digital," as people keep saying about my T.V.. Anyway, I'm now here:

The Resident Djinn Volume II

and hope you'll come by again sometime. Hate losing a reader.

murat11 said...


What a pleasure it always is to walk your Hong Kong streets, and now look out your windows. The tower reminded me of the clock towers of the older dorms at Harvard. Very cool to look at the Dunster tower right outside my big Mather House window about 3 in the morning. To my eye, that's a lovely tower outside your window, something for the eye to catch, rely on, return to in the days unfolding. Companion piece.

Never know where you're gonna take us next: always part of the pleasure.

I was trying to square the tower and the vegetation with the alley that greets you when you walk out your apartment building. More mysteries.

Here's hoping you are on the mend.

Cloudia said...

Cool to see a post!
Teresa seems to be "in the know"
The rest of us have somply been worried about you.

Yes, up to WWII the chronometer was a crucial piece of equipment.

The loran
now gps....
life goes on. WELCOME BACK pal!!!


Comfort Spiral

Cloudia said...

And do come visitng:
Comfort Spiral

miss ya!!

bindu said...

That was really interesting. I guess I never thought about this problem for mariners. Such an important construction then, but so small and forgotten now ...

Cloudia said...

Where you stay?

Barrie said...

With all that longitude and latitude and algorithms, it's a miracle mariners found their way around at all!

Glennis said...

Very interesting and comprehensive explanation of the signal tower and ball. I am glad you wrote this up as I have visited a similar one many years ago at Lyttleton the port at Christchurch NZ and I had forgotten how interesting it was and how useful it once was.
How nice that you get to look at this interesting place every day, and lovely that the wonder cat has a nice view. Why is he not allowed outside at all? Our cat is not allowed out much, we must be outside too, because neighbours hate cats and we need to protect her, maybe you have a similar problem. Or is Pomme just rather edible?

Richard Wells said...


Sepiru Chris said...

Dear Teresa,

Master Mariners were educated, at Greenwich, and so could read the Philosophiae Naturalis Principia Mathematica by Newton, but I don't ever recall coming across 'Carry on, Mr. Bowditch'. It sounds like a great kid's read. And the book called Longitude sounds like my kind of book, too. So many things, so little time...

I am quite chuffed that my post reminded you of old biblio friends.

As to travel, well... there is a safe port over here...

Dear Barbara,

I thought of you when I was drafting this post. I thought that you might enjoy it. I had intended to do a bit more work on it, but no access in China meant that it posted without my intended revisions. Such is life.

Hello Debra,

The tower is merely a lookout and the space around it is used as a hangout for many of the disenfranchised of Kowloon. Nigerian 'copy watch' vendors, Filipina domestic workers on Sundays, old Chinese gentleman and ladies, and so on.

The slope itself is too unstable for residential construction, or that is what I surmise, otherwise it would have been developed a long time ago.

Dear Richard,

I HAVE been by, or was before I went on involuntary furlough and then on vacation to China, and I shall be back.

Never fear, Richard, I shall be by again. Wild horses would do nothing to dissuade me. Not even cows, of which I have a mild phobia. (They look so tippy and dozy when they are startled and they run in the most ungainly and gravity-defying fashion...)

Dear Murat,

You had best try to square the circle as attempt to reconcile the orthogonally metaphysical, and physical, aspects of my neighborhood, mi amigo.

Your words are exceedingly kind, and very well received.

Hello Cloudia,

I have been absent, and will be back (visiting) soon. Today is the penultimate day of my Dad's visit, so he takes priority, although I know that I have to check up on comments, and then on writings by such lovely writers as yourself.

I strongly suspect that Teresa was commenting based upon my post-anaesthesia haiku the week before this article auto-posted.

Hello Bindu,

Half the fun of observing is dredging the memory banks to work out meanings and uses...

Dear Barrie,

Well, they certainly made some huge gaffs (and not just for fishing). Look at old maps of Africa where the cartographers did not recognize the current that they were caught in, so the Western Hump on the Northern portion of the African continent is severely shortened...

But the tradewinds did a fine job of transporting the adventurous 'there and back again', wherever the winds went...


Not being able to reach the buttons on the elevator on his own is part of the storey, as is the heat, the unliklihood of finding him should he get lost, and the generally poor attitude towards life in much of Asia... And the heat, which Pommes in his fur bound glory is not set to dissipate from his voluminous glory... all good reasons to keep him safe and cool indoors, although he has formally been a field hunter par excellence and has roamed far and wide in Canada, Germany, Switzerland and (shhh) France.


harrywho said...

Interesting to read your comments as I used to live at Blackhead Station up till the age of 5, before moving to Kowloon Tong. My dad was working for the HK marine Department at the time.

I have very fond but vague memories of the place and ahve revisited the place several times on my trips back to HK. Presently I'm in Europe.

Thanks for the story.