Purple and Blue

Every once in a while I'll spy an array of purple glass disks in the sidewalk.  The glass lets light get into underground spaces, but why would they be purple?  Could it be that cheaper glass, made purple with its high manganese content was sufficient?  Some glass turns purple after prolonged exposure to ultraviolet light (or short exposure, much to the dismay of certain pattern glass collectors).  Might that have happened in this case?  Or could the purple have been intentional? 

In 1876 Augustus Pleasanton published The Influence of the Blue Ray of the Sunlight and of the Blue Colour of the Sky, one of the stranger books ever written (California redwoods are tall because of electricity!  Heat destroys gravitation!).   The book touted the health benefits of blue light, and set off a mini-craze of people installing blue windows in their homes.  This is absurd, of course, and the effect was shown to be bunk in 1877.  The glass here at 7th and the Bowery looks pretty worn.  Could it be from the 1876 fad?

Present day so-called "color therapists" others still tout Pleasanton's findings as significant.  Some don't bother mentioning that his ideas were thoroughly discredited.  More fascinating, others mention Pleasanton's ideas as a great leap forward in the history of color therapy, then mention that those ideas, and then continue on as if the idea alone was more important than its absolute dismissal. 

It all makes me wonder about the health effects of Blue:

Comments

[judy]

The top circles remind me of deck prisms used on ships to let the light in. They were clear and not blue and purple.

[Half Glassed]

ZOMBIE POST!

I would bet that it is "sun-purple" glass. It started out clear and gradually turned purple over the years do to the manganese content.

That pic brought back memories of being a kid. I had a flashback to those little glass disks in the sidewalk between the police station & the library. I always wondered what purpose they served. To let light into the "secret place" below the sidewalk.