for laying off parallel widths, for making smaller scales and the like.  In these cases it is substituted for the needle.  In like manner for calculating cross profiles by graphical methods, for reading parallel divisions, for estimating areas, or revising maps, a finely divided prismatic ivory rule, c, can be placed under the glass, B, and will do good service.  In this case the plane of the lens must be perpendicular to the axis of the tube.

[Illustration:  IMPROVED DRAWING INSTRUMENT.]

For draughtsmen a parallel drawing pen, something like b, is used, which gives several lines at once, perfectly parallel and close together; or a drawing pen with which the smallest signatures, such as boundary stones and figures, can be made neatly and exactly, which is secured like the needle, a, and for which the cylinder serves also as pen holder, offers a great advance.

Thus a whole series of instruments can be used with the lens.  For instance, a naturalist can use with it a knife or other instrument.  To avoid injury from the instruments, one should, in laying down the cylinder, place it on its side.  It is also recommended that on the outer tube of the frame, which is appropriately lacquered of black color, white arrows should be placed in the direction of the points of the instrument, so that the eyes shall be protected from injury in handling the instrument, as by the points being stuck into the pupil, owing to lifting the instrument in an inverted position.—­Zeitschrift fur Instrumentenkunde.

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BARLOW’S MACHINE FOR MOULDING CANDLES.

That style of machine for moulding candles in which the candles are forced out at the top by means of a piston is the one most employed, and it is an apparatus of this kind that we illustrate herewith.  In its construction, this apparatus presents some important improvements in detail which it is of interest to set forth.  The improvements made by the Messrs. Barlow have been studied with a view of manufacturing candles with conical ends, adapted to all chandeliers, without interfering with rapidity of production or increasing the net cost.

These gentlemen have likewise so simplified the continuous system of drawing the wick along as to prevent any loss of cotton.  In the next place, the structure of the moulds, properly so called, is new.  Instead of being cast, as is usually the case, they are rolled and drawn out, thus giving them smooth surfaces and permitting of their being soldered, are assembled by means of threaded bronze sockets.  The engravings between Figs. 3 and 4 show these two modes of fixation.  At a may be seen the old method of junction by soldering, and at b the screwing of the moulds into the socket.  This machine consists of a box which is alternately heated and cooled, and which is fixed upon a frame, A, at the lower part of which are located the wick bobbins, E. Toward the top of the machine there is a mechanism for actuating the two pairs of jaws, B, which grasp the candles forced upward by the play of the pistons, D. This mechanism, which is controlled by a lever, acts by means of an eccentric.