Sorry, just had to join the fray...

Maris, I don't understand how you can say that digital cameras don't produce photographs and it gives me great pleasure to continually argue this point.

I assert that Herschel's definition itself proves that fact. "Chemical rays" referred to UV radiation in the past, and so in the context you have adopted panchromatic photography cannot be considered a "photograph". The truth is, Herschel probably would've coined a much less restrictive definition had he any idea of what advancements were to come.

Thanks for posting rhubarb!