"The leading properties of the machine are, that the paddles go forward together to enable the boat to move her a-head, or aft to back her astern, and with half a turn of the wrist they may be feathered. By unshipping one paddle out of the row-lock, she may be pulled or backed completely round. Another advantage is, that by merely taking out the two screws, which is done immediately, the oars are separated, and may be used by two persons as usual. The combined oars also stow in the boat as snugly as the common ones, and can be thrown in or out quite as smartly.'

Reference to engraving, Plate XIX., figs. 1, 2, and 3. Fig. 1 gives an upper view of the rower's handle and the joints. Fig. 2 is a side view of the same; and fig. 3 shews the same on a smaller scale applied to a boat. a a are the oars connected to the handle 6, by the two pair of joints c c and d d. The former allow unlimited foreand-aft motion, while the stops e e in the joints c c prevent the oars from dipping too deeply. By taking out the screws ff the two oars may be immediately disengaged. One of the oars can at pleasure be thrown along the side of the boat, while pulling at the other, in order to pull the boat round. In this case the oar at rest receives no motion from the other, except in a direction to move it fore and aft, which is no inconvenience.

PATENTS FOR COMMUNICATING HEAT.

FROM a desire to encourage constant readers we give insertion to the following letter, though we must confess our inability to discover the precise application of the reasoning. Our correspondent complains of the want of ingenuity in the patented inventions described in our last number, and he adduces Mr. Shand's invention as an example, which he denounces, in the first place, because the patentee is of The Burn, Kincardineshire, we presume it would have been equally bad in our correspondent's estimation if it had been invented at The Hyde, in Middlesex, or The Hague, in Holland, though we cannot precisely ascertain why; but it is condemned, in the second place, because it is identical with the invention described in the Register of Arts, Vol. II., p. 267, new series, alluding to Beal and Porter's new method of applying heat. Now, we have also considerable difficulty in admitting this to be a reason for concluding the invention to be devoid of " ingenuity or importance; " for, if our correspondent should have found Beal and Porter's method of applying heat insufficient, we strongly suspect that he has not made the experiment fairly, as we can from personal observation inform him, and many other constant as well as occasional readers, that the method is both easy in practice and effectual in operation.

TO THE EDITOR.

SIR,-Your Register for the present month is truly a "Journal of Patent Inventions," as it contains descriptive particulars of fifty

nine patents, and the titles of twenty others recently obtained; I must, however, confess, that I have been more struck with the number than with the ingenuity or importance of the inventions you have described. It strikes me, that some among these patentees must have felt the money burning in their pockets, and anxious to get rid of it, have chosen the Patent Office as a place equally amu sing for that purpose, and much more efficacious than a visit to the elephant or the Collosseum. This seems to have been peculiarly the case with one among the tribe, who has taken out two patents in one month, at an expense of many hundred pounds, where no possible advantage could exist beyond what I have hinted at. This gentleman is represented as of The Burn, in Kincardineshire. Now, Sir, although a cockney, I know enough of geography to be aware that this shire is situated somewhere in the Land of Cakes. (Its being honoured as the residence of Mr. William Shand is certainly no reason why it should cease to be called the Land of Cakes.) But I also thought that every shire in that land was intersected by Burns running east, west, north, and south. This gentleman's residence, however, is probably called The Burn, par excellence, to perpetuate the memory of this double burning of the owner's pocket, which sent him on this errand of wholesale profusion to the Patent Office..

Mr. William Shand, of the Burn, in Kincardineshire, if he had travelled with his pipe and crook from his rural retreat, I will not say to London, that would have been a needlessly long journey, but to the Modern Athens, might have consulted fifty scientific works that would have shewn his "" improvements in distillation," separated from their clumsiness and inefficiency, and a modern invention for communicating heat, precisely and in every respect the same as you have described his patent, only that Mr. Shand has ingeniously but unnecessarily contrived a little more work for the coppersmith. If you refer, Mr. Editor, to your No. 41, for August 20, 1828, you will see the identical invention.

Seriously speaking, it really is a pity when persons, who think themselves endowed with inventive powers, do not inquire what has already been effected, before they squander their perhaps hard earnings or painful savings in purchasing for themselves disappointment and ridicule.

I am, Sir,

March 1, 1830.

Your obedient Servant,
And your Constant Reader.

ON COLZA OIL.

Extract of a Letter from Thomas G. Clemson, Paris, to Jacob Green, M. D. Professor of Chemistry in Jefferson Medical College, Philadelphia.

Paris, September 18, 1828.

DEAR SIR,-In accordance with the wish which you expressed when you were in Paris, I send you the following remarks respecting the oil that is burnt throughout France.

It is known by the name of Colza Oil, Huile de Colza, and is extracted from the grain of the Brassica Arvensis, or Campestris, a species of cabbage.

In

The Colza is very much cultivated throughout France and the Netherlands on account of its various and useful qualities. the north of France, and particularly in the environs of Lille, the greatest possible attention is paid by the inhabitants to its production. The seed is sown during the month of July, as we sow our seed for the purpose of procuring cabbage plants. The shoots are transplanted in the month of September-a cloudy day being preferred. A man goes a-head, making holes in the earth, at a distance of about twelve inches from each other; he is immediately followed by a child, who puts into each hole a single plant; a third person finishes the operation by closing the earth around the plant by means of a hoe. When the seed becomes ripe, which generally happens in the month of July of the following year, the plant is cut, tied in small bundles, and put under a shed, or any covered and airy place, to dry. The grain is beaten out, and cleaned in the manner commonly used for the extraction of wheat or other grain, and is then treated for the oil. As the oil comes from the press it may be directly used with potash for the fabrication of soft soap; but if intended for burning, it is necessary that it should undergo another preparation, in order to separate from it its mucilage and the colouring matter which prevents its ready combustion. We are indebted to M. Thenard for the method of purification. It consists in mixing two parts of sulphuric acid (concentrated) with a hundred parts of oil, which are to be well stirred together until the acid combines with the mucilage and colouring matter, which are gradually precipitated in flakes of a blackish green colour, after which a quantity of water equal to double that of the oil is added; the whole is then freely agitated with the intention of depriving the oil of the free acid; it is then left to settle for the space of ten days, at the end of which time the oil which is upon the surface of the water is decanted into tubs, in the bottom of which are holes filled with cotton, through which the oil is allowed to filtre, when it is perfectly pure. This method of purification is applicable to all seed oils. The oil of Colza thus prepared has very little odour, is of a yellow colour, and has a sweetish taste. It is not very soluble in alcohol. When congealed it crystallizes in small needles. diverging from a centre.

Your's, &c.,

THOMAS G. CLEMSON.

Remarks by the Editor of the Register.-This Huile de Colza is nothing more or less than our English rape oil, made from the same kind of plant, and by nearly the same process.