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any quantity of Arfenick equalling in weight between a fixt 
and eight part of the Copper, a greater proportion making 
the Metal brittle^ 
The way, which he tifed, was this. He firftmelted the 
Copper alone, then put inthe Arfenick, which being melted, 
he ftirred them a little togcther^bewaring in the mean time, 
ndc to draw ia breath near the pernicious fumes* After thiSj 
he put in Tin, and again fo foon as that was melted ( which 
was very fuddenly) he ftirred them well together , and im* 
mediately powred them off* 
Me faith, he knows not* whether by letting them ftand 
longer on the fire after the Tin was melted^ a higher degree 
of tufion would have made the raetall porous h but he thought 
that way he proceeded to be fafeft. 
He addfj, that in that metallj which he fent to London^ihcvQ 
was no Arfenick, but a fmall proportion of Silver • as here- 
members,onc fliillirig in three ounces of metalhBut he thought 
withall, that the Silver did as much harm in making the me-- 
tallfoftg and fo lefs fit to be pohfh't, as good in rendring it 
white and luminous* 
At another time he mixed Arfenick one ounce. Copper fix 
ounces^and Tin two ounces: And this au Acquaintance of his 
' hath,as he intimateSjpoliflVc better^than he did the other. 
As to the objeBion^ that with this kind of Perfpedlives, ob* 
jeds are difficultly found, he anfwers in another letter of his 
to the Pjibliftier, of Jan. 6. i6^'» that that is the inconveni- 
ence of all Tubes that magnifie much ; and that after a little 
ufe the inconvenience will grow lefs, feeing that himfelf cculd 
^^readily enough find any day-Objeds, by knowing which way 
they were pofited from other objciSls that he accidentally faw 
in it J but in the night to find Stars , heacknowledges it to be 
more troublefome 5 which yet may, in his opinion, be eafily 
remedied by two fights affixed to the Iron rod, by which the 
Tube is fufteined § or by an ordinary perfpediive glafs faftn*d 
to the fame frame with the Tubtj and direded towards the 
fame object, as Des - Cartes in his Dioptricks hath deferi« 
bed for remgdyfng the fame inconvenience of his beft Te- 
Icfcopes; ' 
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