I cannot help expressing my surprize, that so clear and intelligible an account, of Mr. SMEATON'S air-pump, should have been before the public so long, as ever since the publication of the forty-seventh volume of the Philosophical Transactions, printed in 1752, and yet that none of our philosophical instrument-makers should use the construction. The superiority of this pump, to any that are made upon the common plan, is, indeed, prodigious. Few of them will rarefy more than 100 times, and, in a general way, not more than 60 or 70 times; whereas this instrument must be in a poor state indeed, if it does not rarefy 200 or 300 times; and when it is in good order, it will go as far as 1000 times, and sometimes even much farther than that; besides, this instrument is worked with much more ease, than a common air-pump, and either exhausts or condenses at pleasure. In short, to a person engaged in philosophical pursuits, this instrument is an invaluable acquisition. I shall have occasion to recite some experiments, which I could not have made, and which, indeed, I should hardly have dared to attempt, if I had not been possessed of such an air-pump as this. It is much to be wished, that some person of spirit in the trade would attempt the construction of an instrument, which would do great credit to himself, as well as be of eminent service to philosophy. FOOTNOTES: [11] On this account, if it was thought convenient to introduce a new term (or rather make a new application of a term already in use among chemists) it might not be amiss to call air that has been diminished, and made noxious by any of the processes above mentioned, or others similar to them, by the common appellation of _phlogisticated air_; and, if it was necessary, the particular process by which it was phlogisticated might be added; as common air phlogisticated by charcoal, air phlogisticated by the calcination of metals, nitrous air phlogisticated with the liver of sulphur, &c. [12] Here it becomes me to ask pardon of that excellent philosopher Father Beccaria of Turin, for conjecturing that the phlogiston, with which he revivified metals, did not come from the electric matter itself, but from what was discharged from other pieces of metal with which he made the experiment. See History of Electricity, p. 277, &c. This _revivification of metals_ by electricity completes the proof of the electric matter being, or containing phlogiston. SECTION III. _Of NITROUS AIR._ Since the publication of my former papers I have given more attention to the subject of nitrous air than to any other species of air; and having been pretty fortunate in my inquiries, I shall be able to lay before my reader a more satisfactory account of the curious phenomena occasioned by it, and also of its nature and constitution, than I could do before, though much still remains to be investigated concerning it, and many new objects of inquiry are started.