1317

## **Measuring heat:** *a Prelude to Steam*

The **1317**approach to steam was that it was a means to an end: not just mechanically, but philosophically.

The world needed to get *work done*, and steam was a potential answer. There were other answers that ranged from slavery to magic, and each had a high price. The highest price, however, was to do nothing.

Doing the work of base laborers, eliminating the drudgery (or that was the theory), steam would propel Baldur’s Gate forward.

The concepts of steam engines, which might produce power where wind and watermills failed, had been around for millennia. The first recorded rudimentary steam engine being the aeolipile being invented reinvented countless times by most races. Since then, the few steam-powered "engines" known were, like the aeolipile, essentially experimental devices used by inventors to demonstrate the properties of steam.

A rudimentary reaction steam turbine, the aeolipile ejected steam tangentially from nozzles caused a pivoted ball to rotate. Its thermal efficiency was low. This suggests that the conversion of steam pressure into mechanical movement was known by the ancients.

They also devised a machine that used air heated in an altar fire to displace a quantity of water from a closed vessel. The weight of the water was made to pull a hidden rope to operate temple doors. Some historians have conflated the two inventions to assert, incorrectly, that the aeolipile was capable of useful work.

To really harness the concept of steam power, one had to step back a bit: measuring heat. The thermometer was not a single invention, however, but a development.

The ancients knew of the principle that certain substances, notably air, expand and contract and described a demonstration in which a closed tube partially filled with air had its end in a container of water. The expansion and contraction of the air caused the position of the water/air interface to move along the tube.

Natural Philosophers around Toril created a mechanism to show the hotness and coldness of the air with a tube in which the water level is controlled by the expansion and contraction of the gas. It could produce this effect reliably, and the term *thermoscope* was adopted because it reflected the changes in sensible heat (the concept of temperature was yet to arise).

The disadvantage was that it was also a barometer, i.e. sensitive to air pressure. The challenge was *overcome the air pressure*. Gnomish tinkers may have been the first to make sealed tubes part-filled with alcohol, with a bulb and stem; the first modern-style thermometer, dependent on the expansion of a liquid, and independent of air pressure. Tinkers experimented with various liquids and designs of thermometer.

They also kept the concept of the barometer to record changes in atmospheric pressure – which became very significant regarding the weather.

While artistic, and a curiosity of nature, wasn’t particularly useful until they put a scale on it – and thus was born a thermometer. The scale was a simple gradient between two very important factors in life: the freezing point of water and the boiling point of water.

Registering thermometers were created soon after, marking temperature highs and lows.