3. It must not be decomposed by long-continued exposure to the electric discharge.
These are properties which a priori we should hardly have expected an allotropic modification of hydrogen to possess.
Mendeleef predicted the existence of an element with an atomic weight 3. According to him this element should be intensly electronegative and possess the properties of fluorine to an exaggerated extent. The gas can, however, be kept in glass vessels, which we should not expect to be possible if it possessed more than fluorine's power of combining with glass. I prefer to defer expressing any opinion as to the actual nature of the gas until I have had the opportunity of making further experiments upon it. It is only about two months ago that I found how to get the gas with any certainty, and, as the method involves long bombardments, each experiment takes a considerable time. This has prevented me from making several experiments which suggest themselves, and which ought to be made before coming to a final decision. I thought, however, that the investigation, though incomplete, might not be unsuitable for a Friday evening discourse, as the gas, whatever its nature, is certainly one of considerable interest, and its detection illustrates the delicacy of this new method.
