This might not be in the right forum, but I have a couple of questions regarding the discovery of the photoconductive properties of selenium.
I have read that in 1873 Willoughby Smith was using rods of selenium in checking underwater telegraph cables when he noticed the electrical resistance changed when they were exposed to light. Does anyone know how these rods were used exactly to check underwater cable? Also, from what I can gather, this appears not to have been a new method, so why didn't anyone notice it before?

Google is your friend:
http://books.google.com/books?id=7eUUy8-VvwoC&pg=PA198&lpg=PA198&dq=selenium+use+for+telegraph+cable&source=bl&ots=Jx9GZsVQrL&sig=z3qyFNAue1bvGlbDaMVmgRv-QWE&hl=en&sa=X&ei=Pi1zT-b9DIj5ggfPo4VX&ved=0CDwQ6AEwBg#v=onepage&q=selenium%20use%20for%20telegraph%20cable&f=false

Not today it isn't. The page wouldn't display.

When I was in high school, selenium rectifiers were fun when you exceeded their ratings...

Smelly too, I'd imagine....