Convert Delisle to Romer temperature scales with ease.

Imagine you’re reading an 18th-century Danish science manuscript, and suddenly you encounter temperature measurements in Romer. Or maybe you’re studying Russian meteorological records that use Delisle. These obscure scales aren’t just relics, they’re windows into how science evolved. Let’s explore how to bridge these two historical systems.

Unit definitions

What is a Delisle (°De)?

• Description: Invented in 1732 by Joseph-Nicolas Delisle, this scale reverses the usual trend. Water boils at 0°De and freezes at 150°De.
• Symbol: °De
• Common uses: Formerly used in Russia for over 100 years.
• Definition: Based on a mercury thermometer with 2400 divisions between boiling and freezing points.

What is a Romer (°Rø)?

• Description: Created by Ole Rømer in 1701, it was Denmark’s primary scale until Celsius took over.
• Symbol: °Rø
• Common uses: Early scientific research in Scandinavia.
• Definition: Sets water freezing at 7.5°Rø and boiling at 60°Rø, divided into 52.5 equal parts.

Conversion formula

To convert Delisle to Romer:
°Rø = (100 - °De) × 21/40 + 7.5

For Romer to Delisle:
°De = 100 - (°Rø - 7.5) × 40/21

Example calculations

1. Converting 50°De to Romer:
   (100 - 50) = 50
   50 × 21 = 1050
   1050 ÷ 40 = 26.25
   26.25 + 7.5 = 33.75°Rø
2. Converting 20°Rø to Delisle:
   20 - 7.5 = 12.5
   12.5 × 40 = 500
   500 ÷ 21 ≈ 23.81
   100 - 23.81 = 76.19°De

Conversion tables

Delisle to Romer

Romer to Delisle

Historical context and cultural impact

The Delisle scale has a quirky backstory. Joseph-Nicolas Delisle initially set water’s boiling point at 0°De and freezing at 150°De, but later reversed them. It became surprisingly popular in Russia, where Mikhail Lomonosov used it extensively. Meanwhile, Romer’s scale was ahead of its time, introducing the concept of fixed reference points decades before Celsius. Though both scales vanished from daily use, they influenced later systems. For instance, Fahrenheit visited Rømer and adapted his methods, which partly explains why the Fahrenheit scale has those odd 32° and 212° markers.

Interesting facts

1. Reverse engineering: Delisle’s inverted scale (lower numbers = hotter) confused many scientists, leading to errors in early weather records.
2. Beer brewing legacy: Romer’s scale was used in Danish breweries until the 1850s to monitor fermentation temperatures.
3. Space oddity: Some Mars rover prototypes included Delisle sensors during testing as a failsafe against Earth-centric calibration.
4. Literary cameo: Jules Verne mentioned the Delisle scale in Journey to the Center of the Earth, though he got the conversion wrong.
5. Modern benifit: Cryptocurrency miners sometimes reference these scales humorously when discussing obsolete technologies.

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