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tity of Light; hüt withall its Fumes, raised m the Fusion, like so manyAerial Bubbles, fill the Metal füll of those Microscopical Pores. But WhitcArsenick both Blanches the Metal, and leaves it Solid, without any such Pores,esoecially if the Fusion bath not been too violent. What the Stellate-Regulusof Mars, (which I have sometimes used) or other such like Substance willdo, deferves particular Examination.

To this he adds this further Intlmation, That Putty, or other such likePowder, with which ’tis Polifhed, by the sharp Angles of its Particles, fret-teth the Metal, if it be not very fine, and fills it füll of such small holes ashe fpeaketh of Wherefore care rauft be taken of that before Judgment begiven, whether the Metal be throughout the Body of it Porous or not.

But not having tried, as he faith, many Proportions of the Arsenick andMetal, he does not affirm, which is abfölutely best, but thinks there mayconveniently be used any quantity of Arsenick cqualling in Weight betweena sixth and cighth part of the Copper, a greater proportion making theMetal Britt le.

The way which he used was this. He first meltcd the Copper alone,then put in the Arsenick, which being melted, he stirred them a little toge-ther, bewaring, in the mean time, not to draw in Breath near die pemiciousFumes. After this, he put in Tin, and again, so soon as that was melted,(which was very suddenly) he stirred them well together, and immediatelypoured them off.

He säith» he knows not, Whether by letting them stand longer on the Fireaffer the Tin was melted, a higher degree of Fusion would have made theMetal Porous ; but he thought that way he proceeded to be lasest.

He adds, That in that Metal, which. he lent to London, there was no Ar-fenkk, but a small proportion of Silver ; as he remembers, one Shilling inthree Ounces of Metal. But he thought withal, that the Silver did as muchharrn in making the Metal soff, and so lese fit to be Poliüit, as good in rcn-dring it White and Luminous.

At änother time, he mixed Arsenick one Ounce, Copper fix Ounces, andTin two Ounces j And this an Acquaintance of his hath, as he intimares,Polifht better than he did the other.

As to the Objection, That with this kind of Perspecti ves, Objects are dif-ficulcly found, he anfwers, That that is the Inconvenience of all Tubes thatMagnifie much ; and that affer a little use the Inconvenience will' grow lefs,seeing that himseif could readily enough find any Day Objects by knowingwhich way they were Posited front other Objects that he accidentally faw init. But in the Night to find Stars, he acknowledges it to be morc troublc-lömc; which yct may, in his Opinion, be casily remedied by two Sightsaflfixed to the Iron-Rod, by which the Tube is lüstained, or by an ordinaryPerfpective Olafs fastned to. the lame Frame with the Tube,, and directed ta-wards the. fame Object, as. Des Cartcs in his Divgtrhkj hath deseribedl for Re-• mcdying the lame Inconvenience of his best Teleseopes.

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