In Kind Hearts and Coronets, isn't that also Guinness playing the non-speaking role of the 7th duke in the scene where Louis's father is singing at the castle? And isn't that Dennis Price, who plays Louis, playing Louis's father?
This video (https://www.youtube.com/watch?v=ddx_nsYos1A) from the Royal Society quotes a letter from the 1780's which seems to use 'is a thing' in the modern sense. The reference starts at 04:00.
Also, the site you link to above is at the University of Pennsylvania, not Penn State.
'After all the radiation has, er, radiated', the glass will no longer contain any uranium - it will have decayed into lighter elements. The glass might possibly still glow under UV for other reasons, but not because it contains uranium. Of course, it would take an insanely long time for all the radiation to die down. Natural uranium is mostly 238, which has a half-life of 4.5 billion years, and its decay products (and their decay products, etc.) are also radioactive and would take additional time to decay.
plays Louis, playing Louis's father?
Also, the site you link to above is at the University of Pennsylvania, not Penn State.
http://www.amnh.org/exhibitions/pearls/marine/fossil.html