Cold, hard cash

During 19th-century Lancaster County winters, farmers could sometimes be found plowing the Susquehanna River.

That's right. Plowing the river.

Ice was the dominant crop in January, when Lancaster County's fertile fields lay fallow and the farmers had idle time.

And, while New England boasted numerous lakes and ponds from which to draw its ice, Lancaster County's primary source was the Susquehanna — a major producer, so much so that it helped Pennsylvania rank third in the nation for ice production, behind Maine and New York.

Local historian Lynne Smoker will offer a free presentation on Lancaster County's ice farming tradition at 8 p.m. Tuesday at Elizabethtown Historical Society, 57 S. Poplar St.

Ice, Smoker said, was big business in the 1800s, and in Lancaster County "it was mostly farmers who did it. It was their off-season, and it gave them some work when things were slow."

It was a cold, laborious job, Smoker said, and a fair share of men and their specially cleated horses ended up in the chilly waters. Rescues, he said, were quick and  simple for teams accustomed to working on the ice.

Mid-January was the prime time for ice harvesting, Smoker said. Harvesting season often lasted only two or three weeks.

Unlike Maine, Lancaster County didn't have the luxury of waiting for floes to thicken to 10 or 12 inches, he said. Here, the winter deep freeze was short and uncertain.

"When ice reached a thickness of about 6 inches, they started to harvest," he said. "It's like making hay while the sun shines, because you never know — in a week, it could be down to nothing."

Farmers would use surveying tools to lay out a square or a rectangle on the ice, he said. They removed snow from the surface with a horse-drawn wooden plow, then criss-crossed the ice field, making a checkerboard pattern with an ice scorer.

"Then they'd plow over those lines, back and forth, back and forth, until they were down to within 2 or 3 inches of the bottom," Smoker said. "They'd use an ice saw to finish the job."

Some farmers cut small blocks, while others cut large sheets to be chopped down later. Either way, he said, they'd float the ice down the river, guiding the mini-bergs with special pikes to an icehouse for storage.

"There were a lot of icehouses at the time," Smoker said. "In Columbia alone, there were at least three. They dotted the river shores. ... Most of your communities up and down the river had an icehouse."

Icehouses preserved ice by packing blocks in sawdust, a natural insulator, he said. Well-insulated ice could last through the next November.

In good years, the ice would be exported south — or even overseas. In the 19th century, Smoker said, ice was the nation's second-biggest export, behind cotton.

"But some seasons were very grim," he said. "Sometimes, the ice didn't come at all. Other years, there was 3 or 4 inches and that was it."

That meant residents had to rely on suppliers from upriver, he said — which doubled, or sometimes tripled, the cost.

Ice, Smoker said, wasn't used much in those days to keep one's iced tea properly chilled.

"It was for keeping meats cold, for transporting beverages like beer and milk. It was spread out in market houses to keep the produce fresh," he said. "It was mostly for food preservation."

River ice, Smoker said, is naturally cloudy, and it was anyone's guess what contaminants might have come downriver with the flow.

"People didn't even think about it," he said.

At least, not until technology advanced to the point that allowed for pristine artificial ice, he said. "Crystal-clear ice was a big selling point."

The industry collapsed in the 1920s, when artificially made ice was on the upswing and in-house refrigerators were finally affordable, Smoker said.

Transistors go 3D as Intel re-invents the microchip

At an event today in San Francisco, Intel announced one of the most important pieces of semiconductor news in many years: the company's upcoming 22nm processors will feature a fundamental change to the design of the most basic building block of every computer chip, the transistor.

Intel has been exploring the new transistor for over a decade, and the company first announced a significant breakthrough with the design in 2002. A trickle of announcements followed over the years, as the new transistor progressed from being one possible direction among many to its newly crowned status as the official future of Intel's entire product line.

In this short article, I'll give my best stab at explaining what Intel has announced—the so-called tri-gate transistor. Semiconductor physics are not my strong suit, so corrections/clarifications/comments are welcome. Also, this explanation focuses solely on the "3D" part of today's announcements. Other features of the 22nm process, like high-K dielectrics and such, are ignored. (So if you see a funny term on a slide and you don't know what it means, either ignore it or hit one of the Related Links for more info.)
But before we dive into what's new about Intel's transistor design, we first have to review how traditional transistors work.
In the diagram above, you can see that a traditional "planar" transistor—the kind that was first invented at the dawn of the microchip era, and which has been the norm up until today's announcement—consists of three main parts: source, drain, and gate. (This is actually one specific kind of transistor, a MOSFET, but let's not get too deep into the weeds.)

The device may look odd, but it's really just an electrical switch. Think of the source and the drain as the two slots in a standard electrical socket; if you stuck a conducting wire (like a coat-hanger ) into both of the slots, you'd close the circuit and current would flow (and sparks would fly, flesh would burn, etc... so don't try that at home.) The transistor's substrate is sort of like a magic wire that can either conduct electricity or not, and the gate is the switch that controls whether the wire will conduct or not.

So when a voltage is applied to the metal plate that forms the transistor's gate, a tiny strip of semiconductor material between the source and the drain (our magic wire) changes from an insulator into a conductor, thereby turning the switch "on" and allowing current to flow from the source to the drain. When the voltage is removed, current stops flowing... or, at least, current is supposed to stop flowing when the switch is off. In reality, trace amounts of current will constantly flow between the source and the drain. This so-called "leakage current" wastes precious power and becomes even more of a problem as transistors get smaller and more numerous.

So to recap, the basic idea is that the transistor is a switch that works because a tiny bit of insulating material between two "electrodes" magically morphs into a conductor when a voltage is applied to it, thereby closing the circuit.