Gennai-ki: Hiraga Gennai Memorial Day

What Is Gennai-ki?

December 18th is Gennai-ki, the memorial day of Hiraga Gennai -- a naturalist, Dutch-studies scholar, writer and inventor of the mid-Edo period. Born in 1728 in Shido, Sanuki Province (today Sanuki City, Kagawa Prefecture), he died in Edo on the 18th day of the 12th month of Anei 8, which corresponds to January 24, 1780, in the Western calendar.

A Man Who Fit No Single Title

Hiraga Gennai was a naturalist and geologist, a Dutch-studies scholar, a physician, an industrial promoter, a joruri playwright, a haiku poet, a Western-style painter and an inventor. He worked under many pen names, including Kyukei and Furai Sanjin.

• Lifespan: 1728 to the 18th day of the 12th month of Anei 8 (January 24, 1780)
• Birthplace: Shido, Sangawa District, Sanuki Province -- now Shido, Sanuki City, Kagawa Prefecture
• The elekiter: he is known for repairing a static electricity generator, reportedly succeeding without fully understanding its principle
• Other work: making what is regarded as Japan's first thermometer, and developing kakanpu, a fireproof cloth
• Pen names: Kyukei, Furai Sanjin and many others

The Eel and the Day of the Ox

There is a theory that Gennai popularized the custom of eating eel on the midsummer Day of the Ox, having devised an advertising line for an eel shop struggling through the summer. It is passed down as one account among several rather than an established fact.

Tips for Marking This Day

• Look up photographs or replicas of the elekiter to see what the device was
• Read about how far Dutch studies had advanced in the Edo period
• Compare a few of the competing accounts of the eel custom's origin
• Consider what it means to work across more than one job title

An Edo Talent Who Refused to Stay in One Box

Gennai's projects are often said to have stopped just short of practical use, and opinion on him remains divided. Even so, few people have reached into so many fields at once. December 18th is the day to recall his name.