22

was at the same period. Children lose -weight during the first three days after

their birth; at the age of a week they

begin sensibly to increase; after 1 year

they have tripled their weight; then they require 6 years to double the weight of 1 year, and 13 to quadruple it.

To calculate the burden of an edifice, or a bridge, covered with a crowd, it is well to know, that the mean weight of an individual, whatever is the age or sex, is about 98-584956 lbs. avoird.; that is, 103.65756 lbs. for the males, and 93 7328 lbs. for the females.

The inferior parts of the body are developed more than the superior. In a child the head is equal to a fifth part, and in a full-grown man to an eighth of the whole height of the individual. These proportions vary a little among different nations.*

April 2.

CHEAP GALVANIC BATTERY.

1.

A.

Sir, There is hardly any apparatus more acceptable to the experimental philosopher than an effective galvanic battery; but the price usually demanded for these instruments is such as to keep them out of the hands of all but the wealthier class of experimenters. The following description will enable any person, by the help of an ordinary brasier, to obtain a cheap galvanic battery, adapted to all the purposes for which such an apparatus is required. It is well-known that the general appli

From a paper in Jameson's Edinburgh Philosophical Journal. Jan. April. 1834.

cations of galvanism require two modifications of it, usually obtained by two distinct sets of apparatus. Thus :-either a large quantity of the galvanic fluid is required of feeble intensity, as in Dr. Hare's calorimotor, or in electro-magnetic experiments, for which a single pair of plates of large dimensions is used; or else a small quantity of the fluid is required of sensible intensity, as in chemical decompositions, or medical applications of galvanism; for which purpose it is necessary to employ a considerable number of pairs of plates, or alternations of copper and zinc, of small size.

The apparatus, of which I have prefixed a rude sketch, is susceptible of either of these modifications, so that it may be converted at pleasure either from a caloric or electro-magnetic battery to a chemical one, or the contrary, in a few minutes, and without any soldering or other tedious process.

The copper plates are double cylinders soldered together at the bottom, like that first described (I believe) by Mr. Sturgeon, having between them cylinders of zinc, which are kept from contact with the copper by pieces of wood at the bottom and sides. To each of the zinc cylinders, as well as to each of the outer copper cylinders, are soldered, on opposite sides at the top, a pair of flat copper sockets, into which a thin slip of copper may be inserted for the purpose of connecting the different pairs of plates. The interior of these sockets must be silvered with nitrate of mercury, as must also the extremities of the copper slips which are inserted into them, and should also contain a drop of fluid mercury at the bottom. The copper slips being bent into arches are to be inserted into the flat sockets, as in the above sketches, where the dotted lines denote the sections of the zinc cylinders, and the rest those of the copper cylinders.

If a chemical battery be required, insert the slips or arches as in fig. 1, which represents a battery of three pairs of plates-if a calorific or electro-magnetic battery be required, insert the arches as in fig. 2, which evidently represents a battery of a single pair of plates. It is hardly necessary to add, that a variety of combinations may be made out of the same set of cylinders, affording any required modification

66

Sir, Mr. Cheverton's dreadful infiction-HIS ROD hath, at last, fallen upon me, without his own character or the good taste of your readers being, in the slightest degree," ill-consulted "without the most distant apparent inclination to render your pages the medium of a personal quarrel between himself and me! HE will not descend to imitate my dull-vituperative style! HE would shudder to characterise an opponent as a coarse practitioner from the abattoir !"- a mere hacker of flesh and bones."! He is a man of more gentlemanlike bearing than to fume out false accusations! No, Sir, HE stands upon too lofty an eminence! His philosophic and refined understanding could not possibly stoop to mere personal abuse, or controversial subterfuge! No, HE is the very prototype of wisdom! -an immortal emblem of refinement!a breathing picture of urbanity and peace!-gentle as a lamb-sweet as honey-mild as new milk-" parfaite amour in toto! HE is not the cur who, when he meets with an unflinching antagonist, flies growling and barking to his kennel!-HE is not the tamehearted pugilist who swears that a blow is false because he cannot parry it!— nor is HE slippery as the eel, which, by its twistings, and its twinings, and its slime, evades the grasp of its pursuer, and buries itself in its native mud! No, Sir, Mr. Cheverton is a being of far different stamp!-his mental qualifications-his scientific reputation-his temper-his writings-his sentiments-will all bear the test of the most rigid scrutiny! His theories will all be established by practical results! The halo round HIS head will brighten as each opinion becomes confirmed by experiment! In a word, HIS letters on the undulating

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23

railway," while they will immortalise the fame of the Mechanics' Magazine, will become never-dying monuments of sterling talent and correct observation, from the hour when that trial takes place, which a DALTON* has been indiscreet enough to recommend! Till that hour arrives, I almost feel inclined to "leave him alone in his glory," in order that I might, with double effect, magnify his transcendent name, and prostrate myself before this living monument of wisdom! But-[ cannot resist the inclination, which bis last letter has excited, to pay him some passing homage; for neither the " warwhoop of the Mohawk "-nor the "inspiring blast of the clarion," shall be compared to the sounding of his brass, or the tinkling of his cymbals!

Yet how shall 1, to whom "nature has been so niggardly," sufficiently extol the praise of one, who, declining to quarry all ignoble game, is able to defend himself against a weapon capable of dividing" soul from body," the very marrow from the bones."?

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Immortal champion!-inspired philosopher!-tender and kind-hearted victor! may this humble panegyric be a memento of my deference to thy fame, as long as the Mechanics' Magazine may survive the wreck of time-and may that be for ages!

Having thus, Mr. Editor, in sincere good humour, squared one part of my account with Mr. Cheverton, I beg to acknowledge, like him, the gratification which I feel at the prospect of this toolengthened controversy being terminated. The venom which he thought it prudent, in the first instance, to cast on me, I good-humouredly endeavoured to throw back; but his last effusion was of so different a nature-so characteristic of a noble and unoffending disposition, that I have met it, as it deserved, with an unbounded expression of veneration. As you have admitted, in your valuable columns, his unmeasured declamations, I trust that equal justice may be done to me; and that you will, by publishing this reply, permit me the opportunity of proving that he who cannot, by fair and manly argument, defeat a lite

Alluding to the trial of the undulating railway, which Drs. Dalton and Lardner have recommended to be instituted on the London and Birmingham line.

rary or scientific opponent, stands little chance of doing so by an opposite course of conduct.

Such was my object in noticing Mr. Cheverton's extraordinary letter (vol. xx. page 73). Had it been otherwise, my silence should have shown my contempt for the vulgar sneers and false accusations with which that document abounded. But it is passed, and I congratulate Mr. Cheverton on the victorious result of his attack.

As no unnecessary time will now be lost in trying by ample experiment, on some line or other, the merits of the undulating question, I would propose to your readers in general, that all further controversy should rest until the experiment be made. Practice can alone determine whether I or my opponents have been right or wrong in our anticipations, and whether Mr. Cheverton's arguments or mine will be creditably substantiated. The note which you have attached to my last communication, leads me to hope that you may concur in my present opinion ;* and if so, while Mr. Cheverton may try at his leisure any further experiments he may please at the National Gallery of Practical Science, I will direct my attention to the means of elucidating the problem in a far more satisfactory way. If, on a trial being made, I find myself in error, I will frankly confess my incompetency to argue this subject, and my folly, at having so warmly and so boldly espoused it-if otherwise, I trust there are many of your readers who will give me credit for some patience, and for some intellectual capabilities beyond the canaille sphere in which Mr. Cheverton has been so anxious to place me.

The test shall not be less difficult than I originally proposed.-Whether the experimental railway be 6, 8, or 10 miles in length, I maintain, that any locomotive engine will traverse an undulating line with a load which is its maximum load on a level, in half the time which it will occupy in traversing the same distance with the same load on a dead-level railway, and without greater waste or

We do perfectly; but it must be with reservation of the claims of Mr. Whitehead and Mr. McKinnon, to whose papers, in opposition to the undulating system (now many months in hand), we stand pledged to give insertion. We shall be glad to have their assent to the postponement proposed in the text.-ED. M. M.

consumption of fuel. And I, moreover, say, that any locomotive engine will tra verse an undulating line at a great velocity with a load which that same engine cannot move upon a level line.

Whenever this trial may take place, your readers shall have ample notice of it; and if you, Sir, will undertake the office of umpire, I shall cheerfully abide by your decision.

In the mean time, it would be mere repetition, and an unnecessary prolongation of our arguments, were I to reply at length to the more solid parts of Mr. Cheverton's last letter. One or two points, however, I cannot help touching upon.-First, as to "locomotive duty," which he so frequently harps upon. All my arguments, of late, have been almost confined to the practical consideration of locomotive duty. I do say that by employing gravity as an auxiliary force, we save locomotive power. What! Mr. Cheverton exclaims, can you take advantage of gravity without being obliged to repay what you borrow? Yes, is my replyand yet no perpetual motion, Mr. Cheverton! How? Mr. Cheverton would ask. My answer is simply this, and whether it be true or false, experience will prove— velocity is gained by taking advantage of gravity. Friction on railways is, in my humble opinion, not as the spaces, but as the times or velocities. If this be trueand if a greater velocity be attainable on an undulating than on a level railway, there is (exclusive of any difference in friction arising from the particular inclination of the plane) less friction on an undulating than on a level railway. Locomotive steam power is therefore saved.

The next point I wish to allude to, is Mr. Cheverton's observations about a lecture given to me, or some of my acquaintances, by Professor *******, in the National Gallery. Does he mean Professor Ritchie ?-if so, I was not present. That gentleman and Mr. Locke had, I know, a conversation together; but the only time that I have had an opportunity of conversing with Professor

* It will occur to your readers that I have frequently stated as my opinion, that an engine would convey, on an undulating line, at least twice the load which the same engine could move on a level, at the same velocity. Such is my opinion now; but the test which is above proposed will, I am sure, be deemed sufficient to decide the question at issue, and it will be found to accord with the terms of my original challenge.

Ritchie on the subject, was recently, when he did me the honour to spend part of the day with me in Liverpool. In a word, the only individuals whom I can call to mind as having expressed a decided opinion in my presence, when in London, adverse to the undulating railway, were Mr. Saxton and a friend of his, whom I begin to think was Mr. Cheverton; and as to any acquaintance of mine then present being afraid of their

65

badgering," I rather think Mr. Cheverton has imbibed an erroneous impression. If it were necessary, I could publish, in this letter, a list of persons who are advocates of the undulating railway, amply sufficient to out-balance the strongest testimony which Mr. Cheverton and his friends can advance against it, but the best testimony is practice, and upon that I throw the merits of the case.

Lastly, Mr. Cheverton offers some important practical objections, which I confess to be more worthy of notice than any points which he has hitherto advanced. But, serious as they appear, they will not, on consideration, be found of any real weight. In the first place, we have to determine what is a safe velocity-that being determined, how can it be attained on a level railway with heavy loads? Unless gravity be employed at starting, as an auxiliary force, a much more powerful engine would be requisite to move a heavy load from a state of rest, than to continue it at a given maximum velocity; and if gravity be employed at starting, the engine and load must ascend again to a like summit, in order to maintain the starting advantage; and if so, what is this but an undulating railway? Does Mr. Cheverton imagine that a perfect cycloid, or a perfect arc, alone constitute my idea of an undula tion? Far from it-he may descend a hill, run four miles on a level, and ascend to an equal elevation; and by doing this would realise a system of undula

tion which might, probably, be adopted

with advantage in some cases; for, with heavy loads, a velocity might be generated by the first descent which could not, with the same engine, be generated on a dead level; and this being maintained on the level, would enable the load to ascend to a like elevation. But supposing the undulations to be a series of regular segments of circles, wherein consists the difficulty

25

of sustaining an average velocity of 20 or 30 miles per hour, without an increase of speed? Is it necessary to work the engine down every descent? One of the leading advantages which I anticipate, is the great saving of that steam expenditure which is now necessarily incurred in maintaining high velocities on a level. Again, it will require very powerful engines to attain high velocities, with heavy loads, on level railways: whereas, such powerful engines will not be so necessary on undulating railways, and for the reasons previously stated.

I now, Sir, unless again attacked by Mr. Cheverton, close with pleasure this twelvemonths' warfare, anxiously awaiting the result of practical trials; and sincerely hoping, although a few waspish observations have occasionally intermingled with a subject to which they should have been altogether foreign, that some information and benefit may have been derived from the discussion.

I am, Sir, with great respect,
Your very obedient servant,
RICH. BADNALL. J

Douglas, March 27, 1834.

P. S.-S. Y. and I have, in one respect, misunderstood each other. He is certainly right in believing that the pressure upon an inclined plane (alluding to the force necessary to draw a body up) is as the base to the length: therefore, at an angle of 45°, my statement appeared erroneous; but, taking into consideration the resolution of the forces -that at an angle of 45° the length of the base is equal to the perpendicular elevation—and that taking the length of the plane as the entire force of gravity, it forms the diagonal to two equal sides of a square; the oblique forces are therefore equal-that is, at an angle of 45o, the force of gravity which urges a body down a plane, or retards its ascent, is exactly equal to the force of pressure on length, B the base, and F. the elevation, the plane. For instance, if L be the at an angle of 45°, E is equal to B; and although the pressure on the plane B is XL, yet the tendency to descend is

E

L

XL; the one force, therefore, is equal L to the other. I close my discussion with S. Y. with every feeling of respect.

26

PRACTICAL HELPS TO A CHEAP COURSE OF SELF-INSTRUCTION IN EXPERIMENTAL

CHEMISTRY.

Sir,-The extensive utility of chemical knowledge has caused it to be very generally, nay, almost universally, culti vated; but it is a branch of philosophy so entirely founded on experiment, that no person can understand it so as to verify its fundamental truths, unless he conducts experiments himself; it cannot, therefore, be uninteresting to devise such modes as may render the performance of these experiments easy, either by simplifying the apparatus, or by presenting such expedients and resources as shall readily be within the reach of every student. Some one has remarked that no good chemist can have clean hands; I will not admit as much as this, but it is universally acknowledged, that unless he operates himself, propriâ personâ, and conducts his own experiments and analyses, he can be no real chemist. No one could be called a great traveller, who had only read books of voyages and travels by his fireside, though they comprised every one from Sir John Mandeville to Captain Ross. How, then, can we acknowledge a person to be a chemist whose science is founded on the authority of others, and who, when he finds himself in conditions for which he has no precedent in his books, is completely at fault? One experiment, well conducted and carefully observed by the student from first to last, will afford more substantial and permanent knowledge than the mere perusal of whole volumes; and, it may be added, that chemical operations are in general the most interesting that could be devised, were it merely for the sake of amusement.

Let us then proceed to examine some of the "means, and appliances to boot,” that young chemists should possess. Dr. Henry truly remarks, that the notion that a laboratory, fitted up with furnaces and expensive and complicated apparatus, is absolutely necessary to perform chemical experiments, is exceedingly erroneous; in fact, diametrically opposite to the truth. For all ordinary chemical purposes, and even for the prosecution of new and important inquiries, very simple means are sufficient. Some of the most interesting facts may be exhibited by the aid of merely a few Florence flasks, a few com

mon phials, and wine-glasses. Many most important discoveries in chemistry were made by persons who, either from choice or necessity, had recourse to utensils of the simplest character; for example, Dr. Paris, in his life of that admirable philosopher, Sir H. Davy, gives an amusing account of the extasies of the then young chemist, on his receiving an obsolete glyster apparatus from a French surgeon, who was shipwrecked on the coast of Cornwall, and his adapting this clumsy machine to the perforinance of his early and brilliant experiments on light and heat.

For the guidance of the chemical student, I have drawn up the subjoined list of articles which it is desirable he should be possessed of before commencing a course of experiments; several of them might certainly be dispensed with, but from the prices which are also added, it will be seen that the whole are within the reach of persons of even the most moderate means. They may be procured of great purity (and this is highly essential) of Mr. Dymond, 146, Holborn-bars; or of Mr. Davy, 390, Strand. I should recommend that the phials be arranged on narrow shelves, with a slip of leather nailed about an inch from the wall against which the shelf is fixed, and about three inches above the shelf, in which to support the phials. A good sound cork will securely close the mouths, except for volatile or corrosive liquids, for which bottles with ground stoppers are necessary. They must all be labelled according to the chemical nomenclature, as "Sulph. Soda," "Nitrate Putass," &c. Another mode is to label compound bodies according to their atomic composition, by which means the proportional quantities of each constituent is constantly presented to view, and consequently easily borne in mind. For example, carbonate of potass is composed of one atom or equivalent of each constituent; I therefore write Potass + carbonic acid, i. e. potass plus, or added to, carbonic acid. The bi-carbonate would of course stand thus, Potass + 2 carbonic acid, or one atom of the alkali plus 2 of carbonic acid. To resolve them into their ultimate elements is, 1 think, unnecessarily complicated; otherwise the salt in question would stand, Oxide of potassium carbon with 2 oxygen (for