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1825.] though not in an exact way, by heating a little tartrate of lead with potash in a tube in the flame of a spirit-lamp, driving off the water and first products, and raising the residue to dull redness. If a drop of water be allowed to flow down on to the residue when cold, and it be then heated, ammonia will be found to rise with the Water.

I was induced in the course of these experiments to try again and again, whether the potash or lime would not yield ammonia when heated alone; but when well prepared, and the tubes experimented in perfectly clean, they gave no indications of it. By exposure to air for three days in a room, hydrate of lime appeared to have acquired the power of evolving a little ammonia when heated, and caustic lime so exposed gave still stronger traces of it. Potash also exhibited an effect of this kind, and potash which had been heated with zinc, and contained oxide of zinc, most decidedly. Some potash and zinc were heated together; a part was immediately put into a clean close bottle; another part was dissolved in pure water, decanted, the solution evaporated in a covered Wedge wood's basin, and then also set aside in a close vessel for twenty-four hours: at the end of that time the first portion, heated in a tube, gave no decided trace of ammonia, but the latter yielded very distinct evidence of its presence, having apparently absorbed the substance which was its source from the atmosphere during the operations it had been submitted to. White Cornish clay being heated red-hot, and then exposed to the air for a week, gave plenty of ammonia when heated in a tube. When the substances were preserved in well-stoppered phials, these effects were not produced.

Such are the general and some of the particular facts which I have observed relative to this anomalous production of ammonia. I have refrained from all reasoning upon the probability of the compound nature of nitrogen; or upon what might be imagined to be its elements, not seeing sufficient to justify more than private opinion on that matter. I have endeavoured to make the principal experiments as unexceptionable as possible, by excluding every source of nitrogen, but I must confess I have not convinced myself I have succeeded. The results seem to me of such a nature as to deserve attention, and if it should hereafter be proved that nitrogen had entered in some