Philadelphia March 7^th 1796 Having heard that Milton was expected to be at the House of M^r Wolcot where I exhibited to Doctor Priestley the pendulum of my new invented Powder prover & heard that great Natural, Philosopher say "it is far superior to any thing of the kind [for accuracy] I have ever seen in England" in consequence of M^r Franks desire of Seeing it I called on him early this morn, when he informed me he had mentioned it to you Sir & that you expressed a wish to see said apparatus, declaring at the same time your [undecipherable] and those now in practice, and which [undecipherable] for the proving of the publick powder — I wish to know at what time & where I may call, & will be punctual — Sir in the [undecipherable] I must mention the [undecipherable] of my exertions for the attaining the object so [undecipherable] expressed of by me, of the most Learned men this day in [undecipherable] &c. Some years since having never seen eprouvette prover of any kind, & desirous of giving my [undecipherable] and acquaintance Captain [undecipherable] then Superintendent of the magazine of the State, & Saying to him I wished a [undecipherable] had [undecipherable] [undecipherable] it, it is a Powder prover, he produced one, called a Pistol prover the most accurate he was told of [undecipherable] having had it made by an ingenious Artist — [undecipherable] of filling the barrel several times with various grades of Powder & firing it off, I ventured to pronounce the prover erroneous in its principles — "In one or two instances" said he "do you who never saw a prover before pretend to condemn this Excellent prover?" pardoning my presumption Sir, but as truth ought not to be stifled, I will with your permission make it self evident — [undecipherable] the proof he — I [undecipherable] said [undecipherable] [undecipherable] leaving of soft grained [undecipherable] was filled with powder [undecipherable] the [undecipherable] round it [undecipherable] put with a hair [undecipherable] with [undecipherable] [undecipherable] of [undecipherable] for I [undecipherable] the Capt^s suspicions [undecipherable] [undecipherable] would serve the [undecipherable] of strength to the last Season of Summer & the said Season of winter undoubtedly [undecipherable] for [undecipherable] be kept in the [undecipherable] manner — true replied the Captain and [undecipherable] the Same strength in its latter Season was [undecipherable] by simply [undecipherable] directed of employing Spring just as was attached to this pistol prover — truly [undecipherable] he what objection have you to the Spring [undecipherable] against the rim of the wheel" — An incontrovertible objection said I — you are certainly so well acquainted with Natural Philosophy as to know that cold or heat make a sensible alteration in the Strength of Springs, consequently, the very Same powder tried by this prover would be apparently weaker in winter than in Summer, because the Spring would press on the wheel more forcibly, & not throw so high a figure as it would in hot weather, when the Spring being more relaxed would give liberty to the powder to force the wheel further round, therefore, it must be evident the fault lyes in the variation of the Spring — "You have convinced me of that error" said he — "but what other faults are you able to point out" — I object Said I to the Proving of powder by measure, because, (altho I have never tried the experiment) reason points out there might be a greater weight in an equal measure of fine than coarse powder, because the fine lays in closer contact the a solid body, consequently it contains more ingredients, & but a little difference in the quantity of Salt Peter will make an apparent [undecipherable] in its proof — therefore, I am of opinion (if a Critical precision is required in the proving of Gun powder for public [undecipherable]) it ought all to be weighed — it is erroneous to attempt to prove [undecipherable] by putting an ounce of powder with a [undecipherable] & fixing it self to [undecipherable] its strength by the difference it throws an Eighteen pound ball; it may do in Some Sort — but to arrive at a greater nicety a Simple mode might be devised & attended with much less trouble. Such a mode I now have in contemplation — "Very well" reply'd he set about it & if you Succeed, you will meet with [undecipherable] Encouragement — Such a machine I have happily discovered & [undecipherable] [undecipherable] [undecipherable] exception to [undecipherable] principles — the modes of equal [undecipherable] — I [undecipherable] [undecipherable] [undecipherable] [undecipherable] in the proving of Powder, [undecipherable] and [undecipherable] the Same powder be ever so little [undecipherable] [undecipherable] [undecipherable] [undecipherable] [undecipherable] it would [undecipherable] an apparent, [strikethrough: erroneous] case. — I have discovered a Simple method of giving equal & invariable pressure, & which I conceive to originate in my own mind — tis difficult to point it out in writing, therefore will exhibit it when convenient. With respect I am &c. — Joseph Leacock NB Should my machine be adopted by Congress (as it has by our State Legislature) for the proving of all Gun-powder hereafter. I Should pray that a patent might be granted me in order to Secure the invention to my Self — I well remember M^r Godfrey of this City (a [undecipherable] of an existing friend) the whole benefit of his Quadrant — it was Surreptitiously purloined from him — carried to England, & ever after called Hadley Quadrant — Hadley (thro this iniquitous means) accumulated a fortune & poor M^r Godfrey Struggled thro existence in indigence! — Thirty Dollars I am told is the demand of the Office for a Patent, but, alas tis not in my power to pay that Sum, having been exceeding unfortunate in Losing all the Savings of my youthful days by the ravages of a destructive fire, therefore, am reduced to the [undecipherable] necessity of Looking up for help to the benevolent part of my fellow mortals now in prosperity, in order that another American [undecipherable] not be ousted in like manner out of my invention — [Letter from Joseph Leacock [undecipherable] March [undecipherable] 1796] [Recd 1796 Stores From New York N.O. 21]