And they are bound together with a strong wier, applyed across on the concave part, and an hole is cut in the brim with a diamond on one side, of the bigness of a pea, then the crevises are exactly closed in every place with the best lute; which done, a silver or copper ring is to be tyed about it, holding those glasses straightly, so that the Instrument may be fitted to the foot, all which well done, those strong wiers are separated or cut off, with which the glasses were bound at first, namely, near the copper ring: afterward very pure _Aqua vitæ_ is to be put in through a funnel, as much as is required for the filling it up; the Instrument being filled, the hole is shut up, which is to be kept for use; and this Instrument is better than the hollow glass; especially, if it have in its diameter the breadth of one foot, and may be applyed to prospective pictures, it doth excellently represent and multiply them. Behind which, if you place a candle in the night, it gives so much light in the Chamber, that you would think it came from the Sun. It doth also many other things which are here omitted as superfluous. And you may gather the dispersed light in the aire in the night time with it, so that you may read the smallest writing. Such and others of the like things may be done by this furnace, all which to set down, would swell the Book too much. Other things of the metals examination and purification by fusion, in another place. Take this, Reader, which is given to thee, in good part, at another time thou shalt have better; and do not mistake my writings, as if I did reprove the examinations of metals by the Ancients, fusions and separations, who only would communicate my opinion, and yield my assistance for further proceeding; for I know that dealers in metals giving too much credit to their small proof when they find nothing, do, contemn oars as barren, often abounding with gold and silver; when nevertheless, _John Mathes._ says expresly in his _Sarepta_, that minerals oftentimes tryed in a small quantity do yield no gold and silver, which in a great quantity, yield a great deal, wherefore credit it is not always to be given to such tryals, often deceiving, as experience testifies.