Sentence:  the light from <WSD>chlorophane</WSD> is incomparably less intense than that from a common lamp. For there can be no doubt that each of the ten discharges gave a light which lasted brilliantly for six seconds, and upon the whole was equal in duration ... 
Meaning of the word marked with <WSD> tags:  A variety of fluorspar, which, when heated, gives a striking emerald-green light.