proportion to the quickness of the movement, and which the longest practice will not render constantly uniform. He thence concluded, that it was only requisite they should be furnished with an hydrometer, which, by indicating a fixed degree of concentration, would constantly supply products of the same quality; and, after several experiments made in the boilers of this refinery, he gave to the proprietor an hydrometer appropriated to this object, which that gentleman ever afterwards employed as long as he continued the business. Séveral other refiners in France soon constructed similar instruments. In 1782 they were sent to St. Domingo, with a memoir by the author, by M. Louis Dronhin, of Nantes, and they were almost generally adopted there in

1787.

In 1792 M. Bingham carried to Jamaica several of these instruments, which he caused to be made in silver, according to a scale which the author communicated to him at the desire of the celebrated Kirwan.

In the first note, published by the author on the subject of this instrument, in which the description was accompanied by a figure, he gave it a form and dimensions suitable to the capacity of the boilers then in use; but as he soon had occasion to observe, that they could not be used in vessels where the liquid would mostly be reduced at least fourteen centimetres in height (about five inches), he altered it on this account, without making any change in the system of its graduation, which was the easier to be done because it is only on the inferior degrees of the scale that the observation becomes important, the remainder of the instrument serving rather as a handle, or, if desired, will shew the farther progress of the evaporation.

We

We shall here limit ourselves to a description of its new form, (see Fig. 4, Plate II.) after first giving a summary account of the principles on which it is constructed.

The scale of this instrument has been carried to 25 degrees, in order to represent the ordinary state of solu tion in which the juice of the cane, the raw sugar, and the syrup, are put into the boiler.

Experience has shewn that the point of concentration by ebullition, the most favourable to a good crystallisation, is commonly between the third and fourth degree, which determines at once both the quantity of water that the liquor should retain, and the term of elevation of temperature, which cannot be exceeded without decomposing by the fire a portion of the product.

If we wish to see how far this prototype scale corresponds with the aerometer of Beaumé, it may be shewn by calculation, as follows:

This comparison offers an easy method of proving whe ther the first be faithfully executed; but it must not thence be concluded, that the latter can be substituted with the same advantage: this would be to reduce the proportion of twenty-five divisions to eight, which are already not more extended than is necessary for judging with sufficient precision of the coincidence with the level of a liquid agitated by strong ebullition.

The new form adopted for this instrument when used in refineries may be readily understood by viewing the

figure

figure which represents it on a scale of three-fourths of its actual size. To give it a proper degree of strength, the centre of gravity is lowered in the direction of the dotted line a b by means of the ballast placed in the lower part of the ball. The upper part should be perfectly closed, in order that nothing foreign may be introduced when it is entirely plunged in the liquor.

List of Patents for Inventions, &c.

(Continued from Vol. XXIV. Page 384.)

JOSEPH

OSEPH PRICE, of Gateshead, in the county of Durham, Glass-maker; for several new methods of making. glass. Dated May 5, 1814.

JOHN VANCOURVER JEKENHAM, in the county of Middlesex, Esquire; for a method of painting walls of apartments, and other surfaces, by the preparation, use, and application of certain materials for that purpose. Dated May 17, 1814.

THOMAS ABICE PICKERING, of Hackney Terrace, Hackney, in the county of Middlesex; for a method or methods for preventing the loss of parcels (containing bank notes, bank post bills, country bankers or other notes or bills payable to bearer in London or in the country) by coaches so frequently occurring. Dated May 21, 1814.

Specification of the Patent granted to JOHN HANCOCK, late of Reading, in the County of Berks, Gentleman ; for an Improvement in the Construction of Carriages, and in the Application of a Material hitherto unused in the Construction thereof.

Dated August 25, 1813.

To all to whom these presents shall come, &c. Now KNOW YE, that in compliance with the said proviso, I the said John Hancock do hereby declare that the nature and general description of my said inventions are as follows; that is to say: The material hitherto unused in the construction of carriages is whalebone, which I apply partially, or more particularly. The wheels, the circumference, is made of ash, or other timber, and are bound with iron; the spokes are of whalebone, fastened into the wood by mortice and tenon, or by passing the tenon quite through the mortice, divided as though for wedging, and turning each half contrarywise down upon the wood, on the outside, and nailing or otherwise fastening it the nave or box is of cast brass or other meVOL. XXV.-SECOND SERIES.

K

tal.

tal. The axle is iron, and has a collar on it; in the cen tre of which a groove is turned: this collar just enters the back part of the box, on the outside of which a groove is turned with a mortice through on each side, exactly opposite to the groove in the axle. Round the groove in the box two springs are fastened with a bolt or catch formed on the end of each, something resembling those in a common door-lock: these bolts go through the mortice in the box into the groove in the collar on the axle, and are kept down into this groove by the springs. On the outside of the bolts is made a loop to pull them up with, when the wheel is to be taken off. About half way across is turned another groove, wide enough to admit the spokes across; which groove pieces of iron are let in, under which the spokes are passed, so that one piece of bone forms the two spokes; an iron collar is then put on each side of them upon the box, which fastens the ends of all the iron cross pieces, and thus these fix the spokes in the box. When the spokes are thus fixed into the wood or circumference, and into the boxes, each two of them that are formed of one piece of bone are then braced together as tight as possible, in the manner drums are strained, only with iron clips and rivets; the wheels are pushed on the axle, and are fastened by the springs pressing the bolts into the groove in the axle, as before described.

The carriage is made much in the same manner they are generally, only in gigs a piece of whalebone is put between the iron under the shafts, to prevent their breaking; and whalebone is otherwise introduced to strengthen or brace the carriage, as may appear necessary in the different forms, or on which they may be constructed. The springs are made of steel, with bone round, under, or upon them, to prevent their breaking, or of whale

bone