_Laboratory apparatus._--Mine consists of: 1, slab; 2, roller; 3, bottle of benzole (paraffin, turpentine, or solution of washing soda); 4, a funnel, with blotting-paper to act as a filter; 5, printer's ink; 6, rags and duster; 7, a small glass dish; 8, cards to print on. The _Slab_ is a sheet of polished copper, 10-1/2 inches by 7, and about 1/16 inch thick, mounted on a solid board 3/4 inch thick, with projecting ears for ease of handling. The whole weighs 2-1/2 lbs. Each day it is cleaned with the benzole and left bright. [A slab of more than double the length and less than half the width might, as my assistant thinks, answer better.] The _Roller_ is an ordinary small-sized printer's roller, 6 inches long and 3 in diameter, obtained from Messrs. Harrild, 25 Farringdon Street, London. Mine remained in good condition for quite a year and a half. When it is worn the maker exchanges it for a new one at a trifling cost. A good roller is of the highest importance; it affords the only means of spreading ink evenly and thinly, and with quickness and precision, over a large surface. The ingenuity of printers during more than four centuries in all civilised nations, has been directed to invent the most suitable composition for rollers, with the result that particular mixtures of glue, treacle, etc., are now in general use, the proportions between the ingredients differing according to the temperature at which the roller is intended to be used. The roller, like the slab, is cleansed with benzole every day (a very rapid process) and then put out of the reach of dust. Its clean surface is smooth and shining. The _Benzole_ is kept in a pint bottle. Sometimes paraffin or turpentine has been used instead; washing soda does not smell, but it dissolves the ink more slowly. They are otherwise nearly equally effective in cleansing the rollers and fingers. When dirty, the benzole can be rudely filtered and used again. The _Funnel_ holds blotting-paper for filtering the benzole. Where much printing is going on, and consequent washing of hands, it is worth while to use a filter, as it saves a little daily expense, though benzole is very cheap, and a few drops of it will clean a large surface.