TRACT 37.

OF GUNNERY.

211

was found to be near 250 times stronger than the weight orelasticity of the common atmospheric air. He then heatedthe same parcel of air to the degree of red hot iron, andfound it in that temperature to be about 4 times as strong asbefore ; whence he inferred, that the first strength of the in-flamed fluid, must be nearly 1000 times the pressure of theatmosphere. But this was merely guessing at the degreeof heat in the inflamed fluid, and consequently of its firststrength, both which in fact are found to be much greater.It is true that this assumed degree of strength accorded pretty-well with that author’s experiments; but this seeming agree-ment, it might easily be shown, could only be owing to theinaccuracy of his own further experiments; and, in fact,with far better opportunities than fell to the lot of Mr.Robins, we have shown that inflamed gunpowder is aboutdouble the strength that he has assigned to it, and that itexpands itself with the velocity of about 5000 feet per se-cond.

4. Fully sensible of the importance of experiments of thiskind, first practised by Mr. Robins with musket balls only,my endeavours for many years were directed to the prosecu-tion of the same, on a larger scale, with cannon balls; andhaving had the honour to be called on to give my assistanceat several courses of such experiments, carried on at Wool-wich by the ingenious officers of the Royal Artillery there,under the auspices of the Masters General of the Ordnance,I have assiduously attended them for many years. The firstof these courses was performed in the year 1775, being 2years after my establishment in the Royal Academy at thatplace: and in the Philos. Trans, for the year 1778,1 gave anaccount of these experiments, with deductions, in a memoir,which was honoured with the Royal Society ’s gold medal ofthat year, as before mentioned in the beginning of the 34thTract, in the last volume ; where also are stated the resultsof the first experiments, as well as those of the secondcourse of experiments, performed in the years 1783, 1784,1785, 1786.

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