An ingenious Artist of this City has informed me within a few days that he has made a discovery which has been for some time a desideratum both in Science and Commerce. It is connected with the Uniformity of weights and measures, and as that object has been refered to the Secretary of State whose Duties I presume you discharge till you enter on those of your judicial station I do myself the honor to address you on the subject.

The errors produced in philosophical and commercial operations by inaccurate measures of length, capacity and weight have been long a subject of regret. Many premiums have been offered and several attempts have been made to obtain invariable standards for weights and measures, communicable and recoverable at all times, and among all Nations. The apparatus of Mr. Halton was a step towards this end, and Mr. Whitehursts improvements upon that proposition made a nearer approach to the desired object; but Mr. Robert Leslie, a watch-and instrument-maker in Philadelphia, is confident, that he has discovered a perfect mode liable to none of the objections, which are justly made to the two first.

The following statement will place the matter in some degree before you, and will give you most of the ideas which have been communicated to me. The attainment of this desideratum always has been and probably must be attempted by means of the pendulum. Mr. Whitehursts improved method, which is by that apparatus has been found liable to the following objections. 1st. Mr. Whitehurst uses two Pendulums, which requires more time, and occasions greater probability of error than Mr. Leslies mode, who has constructed a single Pendulum capable of being sufficiently varied in length to answer the purposes of the two. The loss of time spent in and the errors incident to the second mensuration are thus avoided, and more perfect accuracy is consequently obtained. 2dly. Mr. Whitehursts ball must be of a given weight and size, and its radius must bear two certain proportions to the two pendulum wires, which will occasion a great number of operations; and must produce a degree of inaccuracy, (where-ever the workmen are not almost perfect) sufficient to destroy that absolute precision which is necessary to the truth of standards. These objections, Mr. Leslie assures me, he also avoids, as his Pendulum may be of any weight or magnitude; and of any convenient length. 3dly. The extreme smallness of Mr. Whitehursts pendulum wire (being less than three grains in weight tho’ eighty inches in length) is such, that it cannot but be bent by the maintaining power (which continues the vibrations) at the place wherein that power acts upon it. This is in effect to alter the length of the wire. Mr. Leslie avoids this objection also, for his pendulum rod may be of any convenient thickness. The simplicity of this new Apparatus, and the facility with which the operation can be performed by it are great advantages, and its accuracy he assures me is perfect.

The Inventor of this Society had thoughts of applying to the Society of Arts in London for a premium of one hundred Guineas, which they have offered these sixteen years for the discovery. But he has determined at least to postpone it, and in the mean time he wishes thus much of the nature of his plan to be communicated to the general Government. If, on digesting the subject to which it belongs, you should desire a Communication of it, I believe I can obtain it from him. If he has been really successful, the Apparatus will probably be the means not only of removing considerable obstructions to the extension of our foreign Commerce, and the progress of general Science but of giving perfection and truth to many important operations of the Mint, the Banks, the Custom house, and the private trader. I have the honor to be with very great Respect Sir, your most obedient humble Servant,