Know the Blow

February 20th, 2008 by Harrumpher Leave a reply »

Depending on who’s talking, the Blue Hills Observatory 10 miles south of our state house is both historical and dynamic. They’ve been doing it since 1885.

Historians and scholars in general manage to justify their study and existence by assembling facts and opinions is various ways. They’ll start a strong declaration, only to becloud it with adverbs, adjectives and qualifiers.

Observatory sunlight deviceWe lucked into a surprise tour from the program director, Don McCasland on Tuesday. It’s not open to the public all that often, but he was so impressed by the nice weather he unlocked the door. For $3 a head, it’s a lot more memorable and visually stimulating that $3 worth of a movie. (Normal open times are 11 a.m. to 4 p.m., weekends, except Dec. and Jan.)

We got to get intimate with the sunlight-measuring globe (description follows). Pix Click Trick: Click on an image for a larger view.

For the history aspect, depending on which historian is saying he can spit the farthest, weather observation has its proponents. Consider:

  • In 1870, the Signal Corps didn’t have a lot of spying and long-distance flag and other manual communication to do. So the War Department expanded their duties to include the nascent field of weather forecasting.
  • Some of those teams apparently made intermittent measurements on Mount Washington. That observatory’s history page conflates that with full-fledged status, as in, “…from 1870 to 1892. The Mount Washington station was the first of its kind in the world, setting an example followed in many other countries.”
  • A wealthy dilettante (Bostonian, MIT grad, family whaling fortune), Abbott Lawrence Rotch, had an interest in weather, the time and money, and maybe no other career ideas. He had the stone observatory constructed at the top of the Great Blue Hill in Milton. It’s been taking and recording measurements since 1885.
  • According to McCasland, when the Mount Washington folk got around to building a station in 1932 for a permanent observatory, they turned to the well established Blue Hill people. Their original instruments were gifts from Rotch’s facility. Some of those are still in use.

Having toured Mount Washington’s station, I admit it is much larger and more elaborate. Until recently, they also had the famous pet cat Nin, who recently retired from the alpine life. BHO has no cat and does not get the intensity of storms.

BHO is a more human and manageable scale though. Upstairs, Robert Skilling has been recording and analyzing for 45 years. The sills and bookcase tops have dozens of manual typewriters and a mechanical abacus, representing well over a century of human intensive analysis. These reflect the daily work there, also a blend of ancient, just old, and modern.

Most of the TV and internet weather relies on the National Weather Service’s Automated Surface Observing System (ASOS). Indeed, there are computers constantly updating displays. While we were there, the NWS sent alarms of small-craft warnings in Boston Harbor too.

The BHO is a hobbyist’s delight though, with old-time devices that worked in 1885 and work now. The BHO records are in binders there (and backed up in files off site, of course). Using the same techniques and machinery for decades makes the comparisons useful and meaningful.

There are electronic barometers, but the world’s oldest continuously (qualifier again) used mercury barometers are still there from 1885 and still read and recorded by eye and hand. Calibrated every decade or so, they remain amazingly accurate.

For one, the wind-speed devices turning on the top of the tower are still mechanical. After one turns 640 times, it trips a recorder, which makes a red line like a polygraph. The quaintness of the system is perhaps epitomized by the clothespins that keep the paper from curling too much. At various points, Skilling or McCasland examines various such recordings and figures out such data as peak wind gusts, average window speed, precipitation and more.

Boston from observatory towerAt specified times of the day, someone goes onto the tower platform to do things such as look at the sky. What parts of the sky have any clouds? How are can you see and how clearly. For example, the State House is 10 miles away, Mt. Monadnock 60 and so forth. We could see Cape Ann very clearly (Gloucester is 36). It must be torture in sleet and high winds.

Don loading sunlight cardPerhaps the singular most fascinating device though is the Campbell-Stokes sunshine recorder on top of the tower. It would be the perfect prop for a Gypsy fortune teller stereotype.

The pic to the left shows McCasland inserting the card for the new series of sunlight readings. Sun, rain, whatever, the cards must be swapped and examined. It was damned windy that afternoon, but he says the pin always keeps the card in place.

Sunlight measuring cardIt is sublimely simple and also blends science and art. One of the BHO staff places a long, heavy, dark paper strip under the globe, holding it safe from the wind with a metal pin. As the sun hits the glass, it does the magnifying-glass thing, burning a hole or erose line in the card. Depending on how bright the sun is, its focused light reaches certain temperatures. Hotter burns a wider space. The pic above shows number three son holding a burned card.

Don and Cindy at sunlight card displayAfter retrieving the paper, Skilling or McCasland can see when the sunlight was bright, brighter or brightest. The temporal measurements are simple too. Each white line represents the end of an hour. And so it has been since 1885.

The pic to the left shows McCasland and my uxorial unit examining example sunlight cards.

Perhaps a future post will talk weather kites.

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