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Description of a Mortar for preparing Mercurial Ointment. By Mr. JAMES PHOENIX, of Liverpool.

Communicated in a Letter to the Editors.

GENTLEMEN,

SEVERAL

EVERAL processes for making Unguentum Hydragyri having been proposed, but which are in general too complicated, the annexed sketch exhibits a mortar for that purpose, which unites simplicity with dispatch.

Fig. 6 (Plate XII.) is a front view of the mortar complete. A is a half section of the mortar; shewing how it should be cut, with a cavity at the bottom for holding the mercury, which by the friction is worked out and in till perfectly oxyded. B B is the pestle, with a wheel (C) in the middle, and two cross bars of iron loaded with lead at the extremities D D, to increase the rapidity of the movement. E, the cramp for fastening the whole together. FF, two uprights to support the handle G in working. G the handle, with an endless screw to turn the wheel C.

I am, Gentlemen, yours, &c.

JAMES PHOENIX.

Improvements on Wheel Carriages.

By Mr. P. ANDREWS.

Communicated in a Letter to the Editors.

With Engravings.

Fig. 7 (Plate XII.) is a ground plaǹ of a waggon, or other four-wheeled carriage. 1 is a pole; 2 2 are two splinter-bars; 3 3 are two chains attached to the extremities of both axle-trees by means of hooks or eyes,

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whose shanks or stems pierce the axle-trees, and are screwed tight by nuts at pleasure; 4 4 are the axle-trees; 5, 6, 7, 8, are the wheels. The two axle-trees revolve on centre bolts in the same manner that the fore axle-tree does in all four wheeled carriages; the chains 3 3 are fixed diagonally from 5 to 7 and 6 to 8, and take off all the strain or force from the centre-bolts. The chains are so placed, that the one is the whole width of the axle-trees above the other, therefore do not touch each other, and the parts of the chains are always comparatively at rest amongst themselves, consequently take off all friction. As the chains take off all strain or force from the axle-` trees, those parts may be made much slighter, and the whole fabric of the waggon much lighter. The wheels may be made of any height, either to pass under the waggon or to lock into a nook in the side. They should be cylindrical; and the fore axle-tree, if those wheels pass under, should be shorter than the hind axle-tree by the breadth of the fellies; or if the fore wheels lock into the side then that axle-tree should be so much wider; by this method the wheels would have different tracts, and be of great service to the roads, as they would cover twice their own breadth on the fellies, and operate as rollers. From the position and effect of the chains the centre of gravity, of motion, and of draught, is in the same point, consequently (if the wheels are of the same height which they should be) the line of draught will be horizontal, and in every possible position a straight line; therefore such a carriage cannot be overturned unless it should be drawn on any bank, &c. whose elevation shall exceed forty-five degrees, and will run much lighter, and with less force, than any other carriage,

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carriage. It will describe a circle round a point, therefore may be turned round on its own length of ground, and in a sharper angle than any other carriage can. Either end may be used as the fore end at pleasure, by merely shifting the pole or shafts, therefore all obstructions and stoppages are avoided. This carriage is admirably caleulated for timber, as the line of draught is straight forward in all positions; the timber will be carried forward nearly half its length in the act of turning any angle, therefore such timber may be turned on this carriage where no other can. It is also well adapted for the conveyance of siege artillery or pontoons, as in case of necessity (which often occurs abroad, where such carriages, &c. must be long delayed, or perhaps abandoned to the enemy), the pole or shafts may be shifted in one minute, and the carriage retreat in safety.

Fig. 8 is the ground plan of an expanding axle-tree, adapted to various purposes in agriculture. is the pole; 2 the wheels; 3 3 two bars of wood that cross the square frame, and extend and join to 4, which is a harrow, rake, or drill, with two joints 10, 10, which move both ways, so that when the carriage is in use the harrow, &c. not only expands with the carriage, but will let its ends fall downwards, so as completely to embrace any ridge of land however convex; also when the carriage is contracted, those arms and joints will cause and permit the harrow to contract at the same time. 5 is a chain or rope which is attached to the square frame at the point or angle next to 5, and extends under the axle-tree to 6, where there is a ring fixed to the said chain or rope. 6 is another ring fixed to the point or angle at 6. By fixing the horse to the ring of the rope

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