by which arrangement the pull will be easier, the impression more even, and the tympan and scraper will last longer. The accompanying sketch represents one of Poirier’s special collotype presses, constructed entirely of iron. The details are so clearly shown in the engraving that after the description already given it will be unnecessary to point out further details. [G] This is necessary only with metal tympans. =White Margins to Pictures.=—To facilitate the production of pictures with white margins, instead of using a mask of paper either oiled or treated with a varnish, an arrangement has been introduced, as represented in fig. 7, the design of which is due to Mr. Raph. Schlegel. The drawing is not perspectively correct, but is made to show as clearly as possible the arrangement and manner of working. The scraper—not shown in the illustration—works on the tympan =O=. =A=, carriage or bed of the press, carrying the printing plate. =B=, a slide of light wood. This prevents the frame =D= and the printing paper =M= coming in contact with the plate before the impression is actually being taken by the scraper. The wooden slide bridges over the plate, and may be 15 to 25 millimetres higher than the plate itself. When the rolling up or inking of the plate has taken place the slide is pushed so far forwards as to allow only just sufficient room for the scraper to rest upon the plate. The action of the scraper during the taking of the impression causes the slide to work out, and allows the paper to come in contact with the print layer. =E E= are adjustable buttons to regulate the traverse of the carriage when printing. =D= is a second frame necessary to carry the strips of thin zinc, =Ef Ef, Eg Eg,= which entirely protect the edges of the paper to be printed upon, and so produce an impression with a white margin. These strips may be almost instantly adjusted to give any required size. The frame =D= must be so much smaller than the frame =L= as to be easily covered by the latter, allowing for the projecting screws and nuts of the clamps =f=. The zinc strips should be reduced to a feather edge on the sides next the picture, and should have secured to them strips of fine paper (foreign letter-paper), which should extend over the edges about three millimetres, to prevent damage to the gelatine layer. =f f= are clamps for the zinc strips =Ef=. They are put through the slots, and the tension adjusted by the nuts. The zinc strips are perforated by two holes at each end, and secured to the clamps by means of screws. =Eg= are also zinc strips; =g= clamps provided with two holes, in each of which a hook is inserted. Corresponding with these a second pair of hooks are inserted in holes in the frame =I=, the hooks being connected together by the strong indiarubber bands =h=. This gives to the strips =Eg= a certain amount of elastic tension. The clamps =K= are also adjustable in slots, and similar to =f=; =L=, frame for the