The apparatus, A, is divided into two compartments, which are separated by a longitudinal partition.  Above the stationary bottom, a, there is arranged a lattice-work grating or a strong wire cloth, b, upon which rests the filtering material, c, properly so called.  The reservoir is divided transversely by several partitions, d, of different heights.  The liquor entering through the leader, f, traverses the apparatus slowly, as a consequence of the somewhat wide section of the layer.  But, in order that it may traverse the filtering material, it is necessary that, in addition to this horizontal motion, it shall have a downward one.  As far as to the top of the partitions, d, there form in front of the latter certain layers which do not participate in the horizontal motion, but which can only move downward, as a consequence of the permeability of the bottom.  It results from this that the heaviest solid particles deposit in the first compartment, while the others run over the first partition, d, and fall into one of the succeeding compartments, according to their degree of fineness, while the clarified water makes its exit through the spout, g.  When the filtering layer, c, has become gradually impermeable, the cock, i, of a jet apparatus, k, is opened, in order to suck out the clarified water through the pipe, r.—­Dingler’s Polytech.  Journ., after Bull.  Musee de l’Industrie.

[Illustration:  SCHURICHTS filtering apparatus.  Fig. 2.]

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LARGE BLUE PRINTS.

By W.B.  Parsons, Jr., C.E.

I send you a description of a device that I got up for the N.Y., L.E., and W.R.R. division office at Port Jervis, by which I overcame the difficulties incident to large glasses.  The glass was 58 inches long, 84 inches wide, and 3/8 inch thick.  It was heavily framed with ash.  In order to keep the back from warping out of shape, I had it made of thoroughly seasoned ash strips 1” x 1”.  Each strip was carefully planed, and then they were glued and screwed together, while across the ends were fastened strips with their grain running transversely.  This back was then covered on side next to the glass with four thicknesses of common gray blanketing.  Instead of applying the holding pressure by thumb cleats at the periphery, it was effected by two long pressure strips running across the back placed at about one quarter the length of the frame from the ends, and held by a screw at the center.  The ends of these strips were made so as to fit in slots in the frame at a slight angle, so that as the pressure strips were turned it gave them a binding pressure at the same time.  In other words, it is the same principle as is commonly used to keep backs in small picture frames.  This arrangement, instead of holding the back at the edges only, and so allowing the center to fall away from the glass, distributed it evenly