You have heard often of the metal called platina, to be found only in South America.  It is insusceptible of rust, as gold and silver are, none of the acids affecting it, excepting the aqua regia.  It also admits of as perfect a polish as the metal hitherto used for the specula of telescopes.  These two properties had suggested to the Spaniards the substitution of it for that use.  But the mines being closed up by the government, it is difficult to get the metal.  The experiment has been lately tried here by the Abbe Rochon (whom I formerly mentioned to Mr. Rittenhouse, as having discovered that lenses of certain natural crystals have two different and uncombined magnifying powers), and he thinks the polish as high as that of the metal heretofore used, and that it will never be injured by the air, a touch of the finger, &c.  I examined it in a dull day, which did not admit a fair judgment of the strength of its reflection.

Good qualities are sometimes misfortunes.  I will prove it from your own experience.  You are punctual; and almost the only one of my correspondents on whom I can firmly rely, for the execution of commissions which combine a little trouble with more attention.  I am very sorry however that I have three commissions to charge you with, which will give you more than a little trouble.  Two of them are for Monsieur de Buffon.  Many, many years ago, Cadwallader Golden wrote a very small pamphlet on the subjects of attraction and impulsion, a copy of which he sent to Monsieur de Buffon.  He was so charmed with it, that he put it into the hands of a friend to translate, who lost it.  It has ever since weighed on his mind, and he has made repeated trials to have it found in England.  But in vain.  He applied to me.  I am in hopes, if you will write a line to the booksellers of Philadelphia to rummage their shops, that some of them may find it.  Or, perhaps, some of the careful old people of Pennsylvania or New Jersey may have preserved a copy.  In the King’s cabinet of Natural History, of which Monsieur de Buffon has the superintendence, I observed that they had neither our grouse nor our pheasant.  These, I know, may be bought in the market of Philadelphia, on any day while they are in season.  Pray buy the male and female of each, and employ some apothecary’s boys to prepare them, and pack them.  Methods may be seen in the preliminary discourse to the first volume of Birds, in the Encyclopedie, or in the Natural History of Buffon, where he describes the King’s cabinet.  And this done, you will be so good as to send them to me.  The third commission is more distant.  It is to precure me two or three hundred paccan nuts from the western country.  I expect they can always be got at Pittsburgh and am in hopes, that by yourself or your friends, some attentive person there may be engaged to send them to you.  They should come as fresh as possible, and come best, I believe, in a box of sand.  Of this, Barham could