There are many theories for why 18th century mugs, or tankards in British taverns often featured glass bottoms. All of them are relevant to our modern worries about privacy and personal safety.
One theory speaks to fear of state intrusion in our lives, as the British Army and Navy would rove taverns and literally abduct drunks into service (called impressment), claiming they’d accepted payment via coins slipped into their beers (a King’s shilling). The glass bottom helped drinkers avoid accepting such trickery.
Another theory suggests that a glass bottom meant you could see your surroundings when taking a gulp, thereby keeping an eye on fists or swords that might come your way. The saying “Here’s looking at you” may have been a toast for such moments of wary distrust in a public space.
A third possibility is that the quality of ale was so iffy that a glass bottom let patrons discover whether or not their drinks were drinkable.
Just think of it: Imbibing in a public establishment in London in 1819 meant fear of government surveillance and overreach, worrying that other people might violate your personal space, and concern that what you consume might be harmful to your health.
Sounds a lot like 2019, only now it’s your phone that’s plated with glass, and it’s not a defense against those threats but rather the enabler of them. And we get to live with them every minute of the day or night.
Makes me want a drink.