[Illustration:  Compound hydraulic press.  Figs. 3 and 4.]

This press is shown in Figs. 3 and 4.  The small rams are arranged at either side of the large ones, which, in this case, are not inverted.  To each of the smaller presses there is a pair of boxes mounted on a vertical column, around which they can revolve to bring either box over the rain head.  When the left hand rams rise, the material is delivered into the cell, D, which previously has had its doors (Fig. 4) closed.  To permit of the cell, D, being moved out of the way, it is mounted so that it can revolve on one of the columns of the main press, first into the position shown at B (Fig. 4), and afterward to C (Fig. 3).  While at D, the bale in the cell (called from its construction a revolver) is partly lashed, the ties or ropes being put into position.  It is then rotated until it comes over the large rams, where the bale is still more compressed and secured.

It must be admitted that this press provides for the greatest possible economy of time, and for the largest output, for the capital employed, which can be attained.  The rams and the men are constantly in action, and not a single moment is lost.  For filling each box 78 seconds are allowed, and there is ample time for the preliminary lashing.

[Illustration:  Compound hydraulic press.  Figs. 5 and 6.]

Figs. 5 and 6 show a modification of this press, designed to turn out sixty bales per hour.  It has only one set of long-stroke rams, with three revolvers.  The bale receives its preliminary lashing while in the position, B (Fig. 6).  Fifty-three seconds are available for filling the box, and the same time for the preliminary lashing.  It is found, however, that three-quarters of a minute is sufficient for the complete hooping of a bale.

[Illustration:  Compound hydraulic press.  Figs. 7 and 8.]

Figs. 7 and 8 show a similar press intended for jute pressing.  This has only one box, which is fixed, as the material has to be packed in an orderly manner.  Its speed is sixty bales an hour.—­Engineering.

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JET PROPELLERS.—­HYDRAULIC PROPULSION OF VESSELS.

Certain mechanical devices appear to exercise a remarkable influence on some minds, and engineers are blamed for not adopting them, in no very measured terms in some cases.  It is not in any way necessary that these devices should have been invented by the men who advocate their adoption, in order to secure that advocacy.  The intrinsic attractions of the scheme suffice to evoke eulogy; and engineers sometimes find it very difficult to make those who believe in such devices understand that there are valid reasons standing in the way of their adoption.  One such device is hydraulic propulsion.  A correspondent in a