We shall try the gases in every possible way. They may be condensed by pressure and rarefied by heat. _Quere_,--would not a powerful injecting syringe,[20] furnished with two valves, one opening into an air-holder and the other into the breathing chamber, answer the purpose of compression better than any other apparatus? Can you not, from your extensive stores of philosophy, furnish us with some hints on this subject? May not the non-respirable gases furnish a class of different stimuli? of which the _oxymuriatic acid gas_ would stand the highest, if we might judge from its effects on the lungs; then, probably, _gaseous oxyd of azote_, and _hydro-carbonate_. I suppose you have not heard of the discovery of the native _sulphate of strontian_ in England. I shall perhaps surprise you by stating that we have it in large quantities here. It had long been mistaken for _sulphate of barytes_, till our friend Clayfield, on endeavouring to procure the _muriate of barytes_ from it by decomposition, detected the strontian. We opened a fine vein of it about a fortnight ago, at the Old Passage near the mouth of the Severn. It was embodied in limestone and gypsum, the outside of the vein, a striated mass; the internal parts finely crystallized in cubes, of the Sp. Gr. 4·1. Clayfield has been working at it for some time. We have persuaded him to publish his analysis in the first volume of the Western Physical Collection. I have made with him the phosphuret of barytes and of strontian: they possess, in common with that of lime, the property of producing phosphorized hydrogen gas; the phosphuret of strontian, it appears, in a more eminent degree. We have likewise attempted to decompose the boracic and muriatic acids, by passing phosphorus, in vapour, through muriate, and borate of lime, heated red. Phosphate of lime was found in the experiment on the boracic acid; but, as no pneumatic apparatus was employed, the experiment was uncertain. We shall repeat them next week. We are printing in Bristol the first volume of the 'West Country Collection,' which will, I suppose, be out in the beginning of January. Mrs. Beddoes hopes that Miss Giddy received her letter, and desires me to certify that she wrote almost immediately after the reception of her epistle. She is as good, amiable, and elegant as when you saw her. Believe me, dear Sir, with affection and respect, Truly your's, HUMPHRY DAVY. [20] Here the reader will recognise the force of early associations. The work announced in the above letter was published in the commencement of the year 1799, under the title of "Contributions to Physical and Medical Knowledge, principally from the West of England; collected by Thomas Beddoes, M.D."