The _Ink_ has already been spoken of. The more fluid it is the better, so long as it does not "run." A thick ink cannot be so thinned by adding turpentine, etc., as to make it equal to ink that was originally fluid. The variety of oils used in making ink, and of the added materials, is endless. For our purpose, any oil that dries and does not spread, such as boiled or burnt linseed oil, mixed with lampblack, is almost all that is wanted. The burnt oil is the thicker of the two, and dries the faster. Unfortunately the two terms, burnt and boiled linseed oil, have no definite meaning in the trade, boiling or burning not being the simple processes these words express, but including an admixture of drying materials, which differ with each manufacturer; moreover, there are two, if not three, fundamentally distinct qualities of linseed, in respect to the oil extracted from it. The ink used in the laboratory and described above, answers all requirements. Many other inks have suited less well; less even than that which can be made, in a very homely way, with a little soot off a plate that had been smoked over a candle, mixed with such boiled linseed oil as can be bought at unpretentious oil and colour shops, its only fault being a tendency to run. _Rags_, and a comparatively clean duster, are wanted for cleaning the slab and roller, without scratching them. The small _Glass Dish_ holds the benzole, into which the inked fingers are dipped before wiping them with the duster. Soap and water complete the preliminary cleansing. _Cards_, lying flat, and being more easily manipulated than paper, are now used at the laboratory for receiving the impressions. They are of rather large size, 11-1/2 x 5 inches, to enable the prints of the ten digits to be taken on the same card in two rather different ways (see Plate 2, Fig. 3), and to afford space for writing notes. The cards must have a smooth and yet slightly absorbent surface. If too highly glazed they cease to absorb, and more ink will remain on the fingers and less be transferred from them to the paper. A little trial soon determines the best specimen from among a few likely alternatives. "Correspondence cards" are suitable for taking prints of not more than three fingers, and are occasionally employed in the laboratory. Paper books and pads were tried, but their surfaces are inferior to cards in flatness, and their use is now abandoned. The cards should be _very_ white, because, if a photographic enlargement should at any time be desired, a slight tint on the card will be an impediment to making a photograph that shall be as sharp in its lines as an engraving, it being recollected that the cleanest prints are brown, and therefore not many shades darker than the tints of ordinary cards.