My little story here is, to say the least, book mongering. Any natural history book with a one word title is worth taking a look at. The case in point here is ICE by Mariana Gosnell. Alfred A. Knopf (2005). It weighs in at 501 pages! It is encyclopedic. So it needs a subtitle. The author offers: The Nature, the History, and the Uses of an Astonishing Substance. It is a great read.

I report here just a snippet of but one story: the natural history of the icicle. The icicle story begins on page 430. You will not need to read the previous 429 pages to understand the icicle. Then you can take a crack at the cocktail party question: How do icicles get to be icicles. First the obvious, it takes water. Icicle’s cousin, rime, gets its water from the air. When the winds are howling. The icicle gets started as drops of liquid water. Icicles grow fastest when the drip is slowest and fastest when the drip stops. The end of an icicle is the same as the diameter of the drops. The icicle is thus pointy at the bottom with a diameter of the drops that give it life. The release of the heat of fusion in the icicle of keeps the channel liquid and open.

As plates of ice forms on the surface of the drop the making of an icicle has begun. When a drop falls the end of the icicle exposed to the cold air and plate-lets form about 1/10,000 of an inch thick on it and the icicle grows in length maintaining the tunnel –like core remains. On your next visit to an icicle take a paper clip and plunge it up this tunnel and see how long the soda straw shaped tunnel is. The slower the drop rate the faster the tip grows and the longer the tunnel becomes. Slowness is a virtue in the icicle world. You can tell if the icicle is still growing. Touch it and it is wet and soft. As new ice is made from liquid water some 680 calories per gram of water heat is released in and the tip can grow some more.

The length of the icicle grows fastest that the diameter (about 32 times faster). In the icicle world, Long and narrow wins over short and squat. In old age the icicle is shaped like a carrot. Springtime can be a great time for drips to drop of a melting snow-full roof. But remember: Fast drips mean short icicles.

Photo: The anatomy of an icicle’s core. (Photo: Paddy, licensed under the Creative Commons Attribution-Share Alike 3.0 Unported, 2.5 Generic, 2.0 Generic and 1.0 Generic license.)


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