As well as creating beautifully coloured stained glass panes (his favourite shade was deep blue) he was also an illustrator, making his name during the 'golden age' of book illustration along with Beardsley, Dulac, Rackham, and Neilsen.
He died from tuberculosis aged 42, possibly exacerbated by the chemicals used in his glass work.
I have a book of Goethe's Faust, illustrated by Harry Clarke which I took pictures of in order to show these morbidly magical illustrations. He's been credited for inspiring the 'disturbing imagery' of 60s psychedelic art, and now I know that, I can't un-see it in his work:
Enough of this cold cant of future ages,
And men hereafter doting on your pages;
To prattle thus of other times is pleasant,
And all the while neglect our own, the PRESENT.