Philada: 15th. Decr. 1815
By the invitation of Professor Patterson Presnt. of the mint I was few days since highly gratified with a view of the fine collection of mathematical and Astronomical instruments procured in Europe for the U States by Mr. F. R Hassler under the direction of the Secy. of the Treasury.
The number description and quality of the instruments do honor to the liberality of the government and to the talents and judgement of Mr. Hassler to whom the public are indebted not only for the able selection but for several very important improvements (the result of his genius and knowledge) which give to many of them a degree of microscopic accuracy truly admirable and intrinsically important.
The metallic standard measures, are particularly of this description, having attached at each end, a microscope with double reflectors, by which the point of coincidence is ascertained with mathematical precision, and the errors of contact in the usual way avoided; while thermometres attached to the bars, at the same time indicate the temperature of the atmosphere and by inferrence the relative degree of expansion or contraction of the measures.
The pendulum of the clock has also a beautiful contrivance by which the centre of oscillation is not affected by the expansion or contraction of the rod.
The pendulum itself consists of a glass tube at the end of the rod of such length and diametre as shall contain a column of mercury of the required weight, which by expanding with heat or condensing with cold shall raise or lower the centre of gravity in the precise proportion of the opposite effect of the temperature to lengthen or shorten the iron pendulum rod, and thus produce an uniform coincidence in one undeviating centre of oscillation.
Troughton the celebrated mathematical instrument maker in London had said (and so does Mr. Hassler) that there is not so complete and useful a collection of instruments in the possession of any government in Europe: Indeed when viewing them I really thought I had never seen so much intrinsic value for £3700 Sterling which I understand is the aggregate cost.
Mr. Patterson says that Mr. Hassler is not only a profound mathematician and a gentleman of general science and learning but is practically acquainted with with the use and mechanical construction of all the instruments, and has the means and the art of repairing any injury they may sustain.
Considering that our country does not abound with persons so peculiarly qualified to promote the sciences, and that the talent, of Mr. Hassler would be a great public acquisition I take the liberty of recommending him to your patronage and favor. I am told he is at present placed in an untoward situation owing to the want of provision for the compensation of his services under the order of the Treasury Department, and but for the friendship of Mr. Patterson would have sustained great inconvenience.
He is about to visit Washington to state the urgency of his case and I hope and presume that provision will soon be made for his relief.
Allow me Dr. Sir to congratulate you on the consummation of your measures in the auspicious situation and gladdening prospect of our happy country, and to hope that if the invidious contrast which it affords, shall tempt the demon of devastation to reduce us to the common level, we may be found prepared at the threshhold, in the "attitude and armour of defence". Have the goodness to present the respectful salutations of Mrs. Jones and myself to Mrs. Madison and to accept the sincere assurance of the High respect and regard with which I am DSir your Obedt Servt.
DLC: Papers of James Madison.