Are there any French patents set aside on account of insufficiency in the description of the invention ?—I should apprehend very few, in consequence of the ease with which a defect of that sort might be amended.

Supposing an insufficient description is given purposely, with a view of misleading the public, how is it likely to be amended ?—— Then I conceive that the parties could only maintain that as the matter of their invention which they have described. If they have described a great many other things which are of no use, or that are not new, that does not as in England affect the validity of the patent. If there are twenty things claimed in the patent, and nineteen of them should turn out to be old, the twentieth still stands its ground without overturning the patent, which I think would be exceedingly desirable here.

Is it not the practice in some instances in France that the specification should be concealed ?-I am not positive upon that point; it is an expensive thing to gain access to a specification; but I have seen specifications through my agent, who has taken, me to the office.

What is the expense of inspecting a specification ?-Perhaps two or three pounds.

But you are not aware of any case in which the specification of a patent has been entirely concealed from the public?--I think I have heard of such things, but I am not competent to speak to the fact.

Do you think it is a common practice ?—No, I should think not, as a number of the specifications of French inventions are published by the Society at Paris for the Encouragement of Arts.

Then the moment a man has made an application for a patent, his invention is secured to him?-He secures whatever the board chooses ultimately to grant to him from that moment.

Is there any precautionary step that a person can take in France before his views are completely matured, in order to secure priority? -Nothing whatever, but the preliminary specification which I have described.

Then he must, in fact, have gone through probably, in most cases, a course of experiments before he can put in a specification ? -He must absolutely have accomplished something that looks like an invention on paper.

Do you think it would be expedient to mend the law in this country so as to make it similar to that of France in that respect ?—I think it would.

Is it not generally understood that the French specifications are concealed?—I do not know what may be the common understanding; I know it is not the fact. I believe the specifications are not shewn but through a petition, and that causes the thing to be expensive.

Is the petition in most cases granted as of course?—I believe it is of course to a native, but not to a foreigner. I gained access to the specification of an invention which I was anxious to see, because the invention had been stolen from a printing machine which I sent over, and applied to another purpose, (a power loom,) and therefore VOL. IV. NO. 77. 1ST DECEMBER, 1829.

X

I was anxious to see it in order that I might stop the same thing happening here in England, which I did when a patent was applied for here, for the improved power loom.

In the case of a patent being infringed where the specification is concealed, how is the satisfactory evidence given to the court as to what the original invention was?—I presume that the patentee produces his patent which has the copy of his specification appended to it regularly sealed and signed by the proper authorities.

In that case, does his specification at once become public ?—I' suppose it does.

In France, how many commissioners are there?-I do not know there are, I think, ten or more.

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Is it an answer to an objection against a patent in France, that the process has been examined by those Commissioners, and that the patent has been granted accordingly? The Commission sit for the purpose of examining the petition and specification, and they report upon it; which report, if favourable, causes the patent to be issued; but if unfavourable,, from a defective specification, generally calls for further information.

Supposing a patent is attacked in a court of justice, is it an answer to that attack, that the Commissioners have investigated it and have granted the patent, and that therefore any objection to it is precluded?-No; I believe the Commissioners do not take any such responsibility upon themselves, and I do not think it would be expedient that they should do so; I think that that which the Commissioners do is tantamount to that which the Attorney-General here ought to do; he reports that he has examined this subject, and thinks it will be for the benefit of the country that the King should grant a patent; whereas we all know that the Attorney-General is otherwise occupied, and that he is not at all acquainted with any more than the petition.

Then you conceive it is no defence to the patentee himself, to say, that this has been examined by the Commission ?—I think none at all; because, if it was, no patent could be overturned upon any grounds; for the Commissioners having awarded the application, and a patent having been granted, would, upon those grounds, be established as a good one; whereas it frequently happens that, either because the thing has been used before, or has been published before, or upon some other ground, it is overturned.

Are patents ever overturned upon the ground of their not being sufficiently described ?—I think that never can be a ground, because it would be known in the progress of the investigation that such would be likely to be a ground of opposition to it, and the parties would take care to amend it.

Is that the case in England ?—No, it cannot be the case in England; because, in France, the specification is always open, to have a rider appended to it, which is a further explanation of the matter; but in England you cannot alter a single letter which you may even have inserted in error; I have lately been obliged to go over a patent again, in which there was an error of a single letter, only; it was the

word pressing instead of dressing; and I have been obliged to solicit the patent again.

What expense might that have put you to?-The principal fees and stamps being allowed, I should suppose it will ultimately cost thirty or forty pounds.

Do you happen to know whether it is a bar to taking out a patent in France, if they know that that patent is already in existence in another country?—No, that is not a barrier to taking out a patent in France; there is a condition that, when you take out a patent in, France, you shall not take out a patent any where else, or, if you do, your patent in France is vitiated; the same happens in all the other. Continental States, but that is got over with the greatest ease, because you employ your agent, or your brother, or your friend; and so an invention runs through all the countries, beginning in America and coming to England, then Scotland, then Ireland, then France, Holland, Prussia, Austria, and Russia; and that is the course they generally take all the way, under different names, beyond England, Scotland, and Ireland..

Before what tribunal is a patent defended, when it is infringed in France?—I have understood it is before the Court Royal.

Is it tried before a jury?—I believe it is; but I am not sufficiently acquainted with the proceedings to answer that question.

Is the question referred to the Commission ?—No, to the Courts; I know that, because the Courts have differed as to the interpretation of the laws of patents; the Court, in one part of the country, has decided one way, and the Court, in another part, has occasionally decided in another; for instance, it was first considered that the publication of an invention which should invalidate a patent, must be in the French language: it was afterwards determined that, if it was published in any other language, and produced in France, it would vitiate the patent, and it was ultimately asserted (but I do not know whether it was established as the law) that the mere enrolment of an invention in another country, where it was open to the examination of the world, was a publication.

Do you know what is the expense of a patent in France?-It depends upon the length of time for which it is granted; the patents are granted for five, for ten, and for fifteen years; the Government duty upon a five years patent is 300 francs, about £12, exclusive of other fees enrolments, and so on, which are trifling; for ten years. it is 800 francs, which is £32, and for fifteen years it is 1500 francs, which is about £60.

To be continued.

A PRESSURE MEASURE,
By B. BEVON, Esq.

To the practical mechanic, it is often desirable to ascertain the actual pressure produced by various machines and instruments; and it is often desirable to do this in spaces too small to admit the ordinary machines for measuring the force of pressure; such, for

instance, as powerful screw and hydraulic presses, and other machines of that nature. To the screw, and all its modifications, there always belongs a very considerable portion of friction at present not well determined :-the proportion of friction to the gross pressure in the hydraulic-press, has not been satisfactorily ascertained.

Having lately discovered a mode of measuring the actual pressure, in small spaces, with considerable accuracy, Mr. Bevan takes the opportunity of offering it to the public.

If we take a leaden bullet of any determinate diameter, and expose it to pressure between plates of harder metal, made to approach each other in a parallel position, the bullet will be compressed or flattened on two opposite sides in an equal degree; provided the lead is pure, the degree of compression will indicate the amount of pressure. With a graduated press of the lever kind, it will be easy to form a scale of pressure corresponding to the different degrees of compression, until the ball is reduced to a flat circular plate, of about one-fifth of an inch in thickness; and it will be found, that an ordinary bullet of about five-eights of an inch diameter, will require a pressure of near 4000 pounds to effect this degree of flattening. Suppose, therefore, we wish to measure an actual pressure, supposed to be nearly twenty tons, we have only occasion to place ten or twelve of these balls at a proper distance asunder, so as not to be in contact when expanded, and then to measure by good calipers, or other suitable means, the compression of each ball, either by its thickness or diameter, and afterwards add into one sum the particular pressure due to each ball, from the scale first made, by using the lever press before-mentioned.

By this mode he has ascertained the amount of friction of an iron screw press, with rectangular threads, to be from threefourths to four-fifths of the power applied, or the actual pressure has not excceeded four or five tons, when the calculated pressure, if there had been no friction, would have been twenty tons.

The larger the ball, the greater will be the pressure necessary to reduce it to a given thickness. An ordinary leader shot, of one-eighth of an inch diameter, will require nearly 100 pounds to compress it to a flat plate.

By using a ball of five-eighths of an inch diameter, he has found the actual pressure of the common bench vice to be about two tons, when under the same force, if there had been no friction, the pressure would have been eight tons.

In the practical application of these balls, it will be convenient to make a small impression upon them with a hammer, before they are placed between the plates, to prevent them from rolling out of their proper position. This operation will not be found to interfere with the result, as it is the ultimate compression only that is sought, and which is not affected by that of a smaller degree before impressed. This property will also be found very con

venient; for, we may use the same substance several times, by taking care that each succeeding pressure exceeds that of the preceding, in the same manner as Wedgewood's pyrometers are used to measure any greater degree of heat than what they have been formerly exposed to.

It may be observed, that the application of these leaden balls to determine the actual pressure will not interfere with the regular operation of a press, as the articles under pressure may be in the press at the same time the balls are used, which of course must be placed between separate plates.Phil. Mag.

PASSAGE OF CARBONIC ACID GAS THROUGH
A BLADDER.

Observed by THOMAS GRAHAM, Esq., of Glasgow.

In the course of an investigation respecting the passage of mixed gases through capillary openings, the following singular observation was made.

A sound bladder, with stop-cock, was filled about two-thirds up in this flaccid state, into a bell-jar receiver, filled with carbonic acid gas, and standing over water. The bladder was thus introduced into In the course of twelve hours,

an atmosphere of carbonic acid gas. instead of being in the flaccid state in which it was left, the bladder was found distended to the utmost, and on the very point of bursting, while most of the carbonic acid gas in the receiver had disappeared. The bladder actually burst in the neck, in withdrawing it from under the receiver. It was found to contain thirty-five parts of carbonic acid gas by volume in one hundred. The substance of the bladder was quite fresh to the smell, and appeared to have undergone no change. The carbonic acid gas, remaining without in the belljar, had acquired a very little coal gas.

The conclusion is unavoidable, that the close bladder was inflated by the insinuation of carbonic acid gas from without.

In a second experiment, a bladder containing rather less coal gas, and similarly placed in an atmosphere of carbonic acid gas, being fully inflated in fifteen hours, was found to have acquired forty parts in one hundred of this latter gas. A small portion of coal gas left the bladder as before.

A close bladder, half filled with common air, was fully inflated in like manner in the course of twenty-four hours. The entrance of carbonic acid gas into the bladder depends, therefore, upon no peculiar property of coal gas. The bladder, partially filled with coal gas, did not expand at all in the same bell-jar containing common air or water merely.

The jar of carbonic acid gas standing over water, the bladder was moist, and we know it to be porous. Between the air in the bladder and the carbonic acid gas without, there existed capillary canals through the substance of the bladder, filled with water. The surface of water at the outer extremity of these canals being exposed to