obstructions, and you immediately cool his ardour, and render that repulsive which would otherwise be pleasant. While I think it a great defect in the system of teaching adopted by many, that they multiply facilities for indolence, rather than afford increased illumination and vigour to the understanding; the opposite course is equally adapted to retard our progress, and to diminish genius. Supposing B. G. to be an instructor of youth, he must be regarded as a highly-privileged individual, if, under his hands they succeed, every movement which they make, in surmounting obstacles.

Having corrected a rule on Proportion, in proof of his assertions, your ingenious Correspondent adds, "This rule is moreover unintelligible to the learner, as the terms, extremes and means, have never been defined." Now this is by no means a legitimate consequence, unless it can be shewn that the doctrine of Proportion is confined to Algebra. But every one is aware that it forms a part of most publications on Arithmetic. And it is reasonable to suppose, that Messrs. R. and N. took it for granted that the common method of calculation would be known, ere that which is carried on by means of the alphabet would be attempted. In a word it seems to have been the design of these authors, to allure to the study of this beautiful part of mathematics by disengaging its elements, as far as is consistent with propriety, from whatever appeared abstruse. Anxious to introduce the scholar into the temple of Science, they have left it to others to decorate

the exterior of the edifice.

With gratitude for the highly interesting and instructive papers contained in the Mechanics' Magazine, I remain, Sir, Your humble Servant, T. HATHAWAY.

Sheerness, 10th June, 1826.

PERPETUAL MOTION.

SIR,-The interesting subject of perpetual motion, which has crowded the pages of your Magazine with

such various communications, has now for some time been permitted to remain in silence. It has been amusing to observe the different arguments of your correspondents, who have at different times attempted to prove the impossibility of perpetual motion, its improbability, its probability, its possibility, its accomplishment by others, its accomplishment by themselves; but the contradictions in their arguments, the incompatibility of their statements, joined to the circumstance of there not having appeared in your Magazine a single sketch of a machine, which would (upon trial) answer the proposed purpose, have combined to obscure the solution of that much agitated question—can perpetual motion exist?

The consideration of the imperfect state in which the decision of this question remains has induced me to submit the following proposal

"That all those who understand the principles of any scheme for perpetual motion forward it with a drawing to the Editor of the Mechanics' Magazine. That the Editor inform his readers, from week to week, of the number of schemes he has received; and that at length they be published all together, in order to set the question at rest one way or the other, up to the present time. But all arguments against perpetual motion, as they absurdly endeavour to prove a negative, should be rejected."

I beg to take this opportunity of stating my knowledge of the truth of perpetual motion having been accomplished by magnets placed round a circular box enclosing a steel-vaned wheel,* and also that there is now a machine incessantly at work, without assistance, in the famous library at Stutgard, by which a bar (hung by a pivot through the middle) in an upright position, between two pillars, with a ball at each end, the top one being a little heavier than the one below, continues to vibrate by the top ball alternately falling upon

*This scheme was mentioned in a former Number, but no drawing was given, and the description was not perfect enough to construct one by.

VARNISH FOR ELECTRICAL RIBBON. SIR, Seeing in your Magazine of the 25th May (No. 144, page 58.) an article entitled, "Varnish for Electrical Ribbon," wherein your informant states, that the isinglass and India rubber are to be dissolved in alcohol, I beg leave to correct his error. Isinglass being a gelatine, must be dissolved in an aqueous solution, for spirit will have no effect on it; and India rubber can only be dissolved in ether and different oils, none of which will mix with water: the na

ture of each being perfectly contradictory. He has also not stated whether the copal varnish is to be made with spirit or oil, it being practicable either way.

I remain, Sir,

Your constant reader,

87

teeth of a wheel deriving its motion from the arbor of the lathe." Quere. Is arbor the same as mandrell?

In the course of a short time, I intend to make a complete model of my lathe, in order to send to such persons as will, out of pure love to the art, kindly assist me with practical information. For instance, had I a model now ready, I would feel much pleasure in sending it for the inspection of the writer above alluded to, either to his residence, or to your office; having previously affixed to it my humble endeavours of making an apparatus on the plan proposed for the turning of screws. I think this plan of transmitting models of any simple and easily-made machinery would more readily contribute to the acquirement of information, and save much of the pages of your valuable miscellany.

I am, &c.

ON PUMP LEATHERS.

F. B,

SIR,-In reply to the inquiries of T. N. in No. 135, I would recommend the pump leather to be cut out of a whole skin, which has been dressed for the upper leather of shoes. The form to be circular, in order to admit of its moving up and down freely; six inches above, and as much below the joint: he may take the following rule. Suppose the common bore of the pump to be five inches, and the part at the flanch twelve inches, then the diameter of the leather should be about twentysix inches. This will leave about an inch all round, to be screwed into the joint, and six inches to sink downwards, similar in form to a cullender. There will be slight folds at the joint; but the weight of water will prevent their intercepting the action of the piston. The lower edge of the piston should be bevilled, to make the leather fit tighter; and the valve hole be made about four inches square.

I am, &c.

Z.

90

CULTURE OF SILK.

SIR,-Whatever tends to ameliorate the condition of mankind in general, and of our own countrymen in particular, must be a source of congratulation to every feeling mind. Impressed with this sentiment, I am happy to find that efforts are now making to introduce the silk-worm into the Sister Kingdom; and the culture of the white Mulberry Tree, which seems to be so essential to the little animal's existence. I heartily wish success to the attempt, of which I hope, with proper attention, there is but little cause to doubt. By ac. complishing this object we shall have the whole manufacture within our own hands, from the production of the raw material to the finishing of the most costly article. This I should suppose will be a considerable advantage to the different manufacturers in the silk trade, independent of the saving to the country at large. It must ever be a matter of the utmost importance to a manufacturing and commercial empire like this, to produce within itself or colonies as much as possible the raw material of the articles of its manufactures, by which it becomes more independent of other States, retains the balance of trade in its own favour, furnishes additional employment to its population, (an object of the most vital importance to the State,) and also increases the national sources of wealth and happiness.

Now, Mr. Editor, I have always understood that the balance of the tea trade with China is against us, as I believe the Chinese take little or nothing from us in exchange, but receive money for their tea; and I have often thought that this very fashionable and necessary article could be much more advantageously produced in some of our own colonies; for instance, in Van Deiman's Land, or New South Wales, which lie in nearly the same degrees of South latitude as China is in North latitude. I am not aware whether the cultivation of this plant has been tried in any of our Colonies; but supposing the thing practicable (and I cannot see why it should not be so), what an immense

field would be thus thrown open for the profitable employment of British labour and capital. Why should we continue, year after year, to drain our country of its gold, to give to so unsocial a race of beings as the Chinese? If it should be urged, in opposition to this scheme, that it would infringe the East India Company's monopoly, I reply, that Government might still place its cultivation and importation under any restrictions that they may think proper, or the East India Company may still enjoy the extensive trade thereof, under such regulations as may be consistent with the interest of the State. At this awful crisis in our commercial affairs, some new openings for trade are wanting, as well as employment for our overteeming population. The cultivation and management of this plant, would afford this employment to thousands who would gladly emigrate to a genial climate, where proftable labour can be found; and they, in return, would find new wants arise, for articles with which they would be supplied from their native country. The mutual advantages of such a commerce are too well known to require me to dwell upon. Perhaps some difficulty would arise in procuring a supply of the seeds uninjured; but this, I should suppose, with a little dexterous management, may be got over. I hope our present liberal and enlightened Ministry will turn their attention to this subject, not doubting but that, if they think the plan worth a trial, they will give it that encouragement which will ensure its complete success.

I am, Sir, your humble servant,
T. J.

Hammersmith, April 13, 826.

THE POOR MAN'S BAROMETER.

SIR, I have seen many useful devices inserted in the Mechanics' Magazine; and if you think the following description of a cheap Barometer worthy of notice, it is at your disposal:-the whole of the materials of which it is composed may be procured for something less than a halfpenny.