down, till now scarcely any traces of their past existence can be recognised, except by the geologist.. Here (i.e., in the Hebrides) are the wrecks of immense volcanic mountains, formerly some 12,000ft. high and 30 miles wide, in Mull, still higher, and a mile or two wider in Skye...." Mr. Proctor goes on to say that these craters still exist on the moon in their original condition, because they were not exposed long enough to the denuding forces of the atmosphere to become worn down like those on the earth. Surely the crater walls (letter 32299) would naturally fit the interiors if we assume a volcanic origin for them? I should like very much to know of any work where some account of the vast crater remains on the earth, mentioned by Mr. Proctor in the above passage, could be found. There is no mention of them in Greikie's "Class-book of Geology."

Adelaide, S.A., June 16.

E. P. S.

SELENOGRAPHICAL: MERSENIUS. [32564.]-THE accompanying drawing of Mersenius and the neighbouring objects was made on June 18, between 7.30 and 10.30, with a 4in. Gregorian reflector, power about 180. This is an extremely interesting region. Mersenius has no prominent central mountain; but I saw a range running from the north of the east wall, and terminating near the middle; also the east part of the floor is much darker than the middle. The shadow of the west wall was remarkably even. There are three craters on the east wall, none of which are shown on Beer and Mädlers' map. The largest (marked in the drawings) is a fine specimen of subsequent oruption; the second, B, is long and narrow, and by no means as plain as A, and the third, C, required steady looking to see it plainly. Unfortunately clouds prevented me from finishing the drawing of the surrounding formations; but one of the most peculiar features is the bright line running from the crater D right across the Mare Humorum. Westerham Woods, Alumhurst-road, Bournemouth.

C. Roberts.

by assigning to them strongly hyperbolic elements |
being ignored.

One question which occurred to me was-Do any
of these meteors fall into the sun? Four of Mr.
Denning's streams do so, according to Dr. Kleiber's
figures, viz.: one at 47°+ 16' on the 7th of October,
one at 110° +25° on the 4th of December, and two
at 129° 19° on the 21st and 24th of December
respectively. It is strange, if the orbit of this
latter shower passes through the sun, that Mr.
Denning should have observed it twice at an interval
of ten years; yet, on the first of these occasions
the perihelion distance is given as 0.000, and the
meteors were virtually falling in straight lines into
the sun. Such meteors might have their origin in
solar ejection, as the late Mr. Proctor maintained.
The showers at 47° 16° and 110° +25° were only
once seen by Mr. Denning.

Another question is, Do we ever see the same shower at both nodes? There are three or four instances in which it seems probable that we do. There is a fair agreement between a radiant at 20° 58° on the 30th of May and one at 105° + 11° on the 7th of December. The most exact agreement in the elements,, and i, however, occurs between a radiant at 167° +5° on the 16th of February and one at 266°+ 47° on the 22nd of August; but if there is no misprint the difference in perihelion distance is too great for identification. There is a curious instance of two meteor-swarms travelling in opposite directions along almost the same orbit in a shower from 296 +0° on the 11th of August, and one from 31° + 18° on the 12th.

Mr. Denning's Catalogue is not well suited for statistics, inasmuch as it contains many determinations of the same shower in different years. But there are, I think, as many repetitions of showers with retrograde as with direct motions, and therefore the preponderance of direct motions in Dr. Kleiber's list is real. It is more strongly pronounced at small inclinations, and apparently in the case of observations made during the winter half-year. Another remarkable result is the nearness of the perihelion to the node at which the meteors are seen in a great number of cases. Indeed, there are more than 70 instances in which the perihelion distance exceeds 1.000, the earth being, of course, at more than its mean distance from the sun when the observations were made. Other remarkable statistics confirming this result could be easily com

piled.

METEORIC ORBITS. [32565.]-DR. KLEIBER'S book leads to some interesting results as regards the orbits of meteors. It is a pity that the work is in Russian, and that the typographical errors (not corrected in the errata) are I noticed in my last letter the similarity in some very numerous. Perhaps some one interested in the subject will give us a corrected of the elements between the radiant at 60°+59 summary in English. I do not think Dr. Kleiber's on the 16th of August and one at 70° + 66° on the system affords any explanation of stationary or 22nd. Here are the complete elements :long-enduring radiants, which I regard as a well- Radiant. established fact. All the computed elements seem 60° 59° 286.9 to be parabolic-the late Mr. Proctor's explanation 70° + 66° 289.6

П

8

i

144.2

113.5

0.906

149.5

113.4

0 893

WHAT IS THE VALUE OF ALUMINIUM? [32566.1-RE Mr. J. Tracy's letter (32533, p. 456): It appears to me that the "Chemist of 15 Years' Extensive Practice" has not made a strong point against aluminium by his not having had a single use for it. In an experience that to me seems very limited, of four years, I have seen tons of aluminium put in use, and I know that there was a demand for manufactured articles of pure aluminium far in excess of the supply not many months ago. Unfor tunately, all articles like this one Mr. Tracey quotes are anonymous. We may be troubling ourselves to reply to a newspaper reporter who was "padding" his columns.

Re the fourth sentence of the article: Would any practical man decide upon the uses of a metal from 25 cents.' worth of wire or sheet," when the "cheapest metal in the market is 2 dols. 25 cents a pound" (pig metal, of course)? Allowing for the rolling or drawing, it would be a generous man who would sell an ounce of wire or sheet for 25 cents (25 cents is one shilling, 2 dols. 25 cents is about 98.) Can any practical man determine the value of a strange metal from a loz. sample? A Jules Verne used an Al bullet because he knew it practical chemist could analyse an ounce, I know. was good. No practical man could say, as this chemist does, because one metal cannot replace iron, or copper, or tin, it is not worth per pound as much as they. Copper "will not make parts of machinery." Is copper worth less than 14 cents & pound" (7d.)? But we are weary of the chemist and his narrowness. Aluminium has sold for many months at one dollar a pound in New York. It is made into pans and cooking utensils, into ornamented work, into buttons and buckles, and s large number of small articles which consumes the pure metal by the ton. I know one firm whose writer is from New York, and was in the aluminium orders are always for five tons or more. The business there until recently, and is not writing bold (and frank) lies.' The alloys of aluminium are bronzes and brasses What are "frank lies"? superior in strength to any tin alloy, and at the cheaper than any tin alloys. For bearing metal present price of aluminium these Al alloys are and valves a hard, strong, tough bronze, with guaranteed tensile strength of 30 tons per square inch, sells in England at £85 per ton. A brass of over 25 tons per square inch tensile strength which will forge, and is tough and strong when forged, sells at £68 per ton. I quote these prices and strengths from a letter written with no intention to publication, in the course of business.

I am not interested in, nor employed by, any Al
company, though, as I stated, I once was in the
business. It seems to me that these facts will
interest some who were misled by the "Chemist's "
inexperience, and I give them to you simply
because I dislike to have such ignorant statements
made as these by the "Chemist." Pure aluminium
is worth 4s. a pound in England. Does not the
strength of the alloys of aluminium make Al rank
above the value of copper? I think Mr. Tracey
will find few pure metals that will stand sea-spray.
Aluminium alloys are the best-known metals for
use in sea-water. See Engineering, April 13 and
20, May 18, and June 1, 18ss. "What I know,
and no more.'
"

PHOTOGRAPHS IN COLOURS. [32567.1-WHAT a lot we are hearing just now about "Photographs in Natural Colours (see letter 32553), yet what a little we are seeing of it. One Professor after another claims to have discovered a process whereby the natural colours in a subject are reproduced (more or less correctly) in a photographic print. Yet what have these claims led to, and what may they lead to? I am inclined to say that up to the present their only use has been to let off a little of that gas so many (generally minor) professors seem to keep under pressure. Suppose success is ever obtained in this line, how many will be truly pleased with the result? To my mind such searching after the seemingly impossible is a poor way of using one's time. Are the hundredand-one varied results to be obtained from the different printing-papers now on the market so very unworthy of one's efforts?

I cannot believe that it will ever be possible to excel the beautiful appearance of a good platinotype by any coloured photograph, and I am certain that as far as truth of representation goes, at any rate, nothing could beat our present-day prints. In saying these words against the absurd longing for a "coloured picture," I by no means mean to decry such departures as isochromatic plates. I quite side with those who try and get all colours represented with their proper degree of intensity, and I think the nearer we get to this, the nearer we get to the photographic ideal.

How many at the present time are pleased with a coloured photograph-even with a well-coloured one? Yet how will a photograph in colours ever differ (externally, of course) from one of these? I venture to write this in the belief that I am not the only one thinking thus, though I do not know of anyone else who has given expression to his thoughts on the subject.

RAINFALL.

F. E. P.

[32568.]-IN your issue of the 22nd May, '91, you very aptly remark on "the comparative uselessness of generalisation from records of rainfall," and you conclude by saying "that rainfall varies considerably within comparatively small areas." Evidently, then, the remedy is to generalise the records, and the more this is done, the less will be the fallacy when referring to the rainfall of any particular district or country. If numerous rain-gauges were established throughout the country, and then all records sent to one central station or society, what valuable information might be collected for any particular district or country after a lapse of years, and means found for using the superabundant water which falls in one part over another part, where the rainfall is less. Information such as this might be of special value in our larger colonies, allowing of the development of tracts of country which cannot now be utilised. I am quite aware of the fact, that it is done now to a certain extent; but I am inclined to think it is not done so generally as it might be. With the hope, therefore, of aiding some of your readers in a most interesting pursuit, I purpose appending a few notes on rain-gauges which may be of use to the initiated.

=

will enable us to give the amount of rainfall, receiving area with ounces and drachms. To 'do
however large the receiving vessel may be. The this we will suppose the diameter of the circular
edge of the circle, which is usually made of copper top of gauge to be 47in. this squared 22.09,
(as more durable than iron), must be sharp, with multiplied by 7851 17-349486, divided by 1-733
an overlapping rim to prevent raindrops from being an ounce avoir. 1-733c.in.) = 10 011oz. avoir.
whirled out of the receiver, and connected by a
shoulder to a funnel, which directs the water into a
receiver. This may be a glass bottle fitted with a
cork, to hold the funnel firmly, and prevent leakage
between the outside of the funnel and the neck of
the bottle (see Fig. 2). A more convenient
receiver, and one less likely to be broken, is a round
tin case of a convenient size, with a top fitting

Inch.

FE 10oz. = 1.0000

Inch.

loz. =

•1000

9

⚫9000

7dr.

0875

⚫8000

⚫0750

accurately under the overlapping edge of the
funnel-shaped cover. In this large receiver may
be placed a small tin mug with a lip just under the
funnel for conveniently measuring small quantities
of rain, and to prevent wastage from evaporation.
Any overflow from the mug will be caught in the
larger receiver (see Fig. 3). The circle of entry
may, of course, be of any size; but one whose
diameter is between 4 or 8in. will be most con-
venient. Having made the circle determine its
area by careful measurement, which may be done prepared for any larger circle of entry by the same
each square inch will give cubic inches for area.
by the following formula: D2 ×·7854 = area,

Fig 2

As the fall of rain is always measured in inches, gauges are so made as to indicate the equivalent of a cubic inch of rain on the surface of the earth. The simplest form of rain-gauge is a square or circular box or jar with a perfectly flat bottom and perpendicular sides (see Fig. 1). If the depth of water in such a gauge be measured after a fall of rain, we can ascertain the amount of rain that has fallen on the surface of the earth in inches or parts of an inch. Care must be taken that the edge of the gauge is thin and free from dents, and that the sides are perpendicular and bottom of the jar abso- Take this amount of water and pour into a glass, lutely flat, for though in one measurement these marking it at the top of the water, and then irregularities may not make much difference, they dividing the intervening space between this mark would lead to a very decided error in a large number and the bottom into 100 equal parts. This graduated of measurements. Evaporation is also liable in glass will give the rainfall in inches and 100ths of such a gauge to give rise to errors, and extraneous an inch. As, however, an inch glass is somewhat matters are more easily introduced. The better cumbersome, a half-inch glass is usually sent rain-gauges are so constructed as to avoid all these out with a rain-gauge. It may, however, liabilities as far as possible, and depend only on the be of convenience to some to measure with area of entry for the accuracy of the measurements. an ordinary ounce measure, as graduated glass This area may be a square, but is more usually measures, when broken, are not always easily recircular for convenience. The circle must be placed; in that case it will be necessary to find the accurate, and its area is then easily calculated, which corresponding relation between the cubic inches of

A similar calculation can be made, and table method as above. Far Away.

LIEGE AND THE WALLOONS.-II. [32569.]-I FIND I have committed some errors in my last letter, of which your printer apparently approves so highly, that he has added others to his own in the shape of misprints; so that with your permission, I will commence this letter by correcting them, taking the diabolic, or printer's, mistakes first.

(1) "The Countess of Croze" will grate harshly upon the ears of anyone who has read "Quentin Durward," and will seem a funny title for a Burgundian lady to those who have not; so I hasten to say that I wrote "Croye," not "Croze."

(2) Your printer's "Tower of Liége" has no existence, as far as I know; but, at all events, I wrote that the "Countess Isabel was escaping from the town of Liége." Now for my own blunders :(1) I said that "the arms manufacture of Liége exceeds that of Birmingham"; but since then the Vice-Consul has been so kind as to give me a copy of his last report, in which we read:-"Liége exported in 1889 firearms to the value of £724,440, being £233,944 in excess of the value of those exported in 1888"; and, again," the firearms proved at Liége amount to more than double those proved at Birmingham, and to nearly double those of Birmingham and St. Etienne (France) together." I wonder how many thousands of these arms have helped those idiotic Chilians to massacre each other? The Consul at the same time showed really beautifully finished, good-sized Liége revolver, for which he had paid the economical sum of 3 francs, or half a crown! (2) I said that "the Walloons are to be found chiefly in the provinces of Liége and Limbourg." I meant to say Liége and Namur, but I believe the town of Mons also, in Hainaut, is almost entirely Walloon. Belgian, or even Dutch Limbourg, is almost entirely Flemish. (3) John Cockerill was not only an "English Mechanic" himself, but the youngest of three sons of an "English Mechanic"William C.-and was born at Haslingden, in Lancashire, on Aug. 3, 1790. The town that he founded-for it was only a village of 800 inhabitants when he came there-Seraing, has now 34,000 inhabitants, chiefly consisting of skilled artisans and their families. Is there another Englishman in the whole history of the world who can say as much as that for himself? Yet one can scarcely find his name in biographies. (4) I have been talking, since sending my last letter, with the English pro

fessor (a Liégois) of one of the colleges, and he says the Times is almost unknown here, not from any want of appreciation of the English language, but from dislike, or, rather, contempt, of its politics. Liége has always been a very Radical community, and kept the centenary of the brief republic calling themselves "the United States of Belgium," on Oct. 26, 1889, with extreme fervour; but I have always followed the advice of J. J. Rousseau in his "Contrat Social" or "Confessions" (I forget which), and also of Dickens in his "Pictures from Italy," that a foreigner should never mix himself up with the politics of the country or town in which he is residing, which affords him the hospitality of its means and the protection of its police. The professor, however, who speaks English almost without an accent, declares that "the Times is by no means what it used to be the independent leader and just judge of public opinion in England; but is now a mere Tory organ and mouthpiece of Lord Salisbury." He even went so far as to quote the anecdote about the old dramatist Wycherly looking at the picture of himself as a young man, by Lely, while repeating with a sigh the words of Virgil applied to the shade of Hector, "Quantum mutatus ab illo !"-and added "that if there were such a thing as a journalistic mirror, the Times might be supposed to be inspecting it daily with the above apostrophe in its editorial mouth." This remark struck me as being quite true, because I remember the day when the Duke of Cambridge was proud to be seen at receptions, &c., arm-in-arm with the late Mr. John Delane, principal editor of the Times; and when the gallant Field-Marshal Commanding-in-Chief was absolutely compelled (in 1885) to forego his darling project of violently replacing the three Indian Artilleries in India by the Royal Artillery, through two articles in the Times, Mr. Delane having a brother in the Bengal Horse Artillery. (5) Cockerill does not appear to have been the first (as I wrote in my last letter) " to show the Liégois the enormous importance of the paragenesis of coal beds and iron deposits"; but he yields the credit of this appreciation to no common rival-to a no less person than Napoléon Bonaparte himself!

brated Blücher who had come to Liége in 1814 to
inspect the foundry and arms manufacture was
riding along the beautiful avenue of elm-trees on
the Quai St. Léonard, near the foundry, when he was
pursued by a band of "mutinous " Saxon soldiers,
then quartered at Liége, whom the Congress of
Vienna had made over (very much against their own
inclination) to the domination of the King of
Prussia. The mutinous rascals, when the old hero
went to them to tell them they must change their
cockade,' called out loudly to kill their new general,
and when he turned his bridle, ran after him at a
racing pace, stabbing at him with their bayonets.
Luckily for him the gate of the foundry was open; he
galloped in, and it was immediately closed after him
by the Prussian sentry. This would have been the
finish of the man who, some months later, made
himself illustrious for ever on the field of Waterloo."
A Countryman of John Cockerill.

INCORRECT CRITICISM.
[32570.]-I MUST ask space to refute the gra-
tuitous, unfair, and incorrect statements of your
correspondent "G." on p. 483, the self-elected
critic of matters nautical. He is kind enough to
compile a list of those who, he says, gave correct
and incorrect replies to a given query. I regret to
have to say, in defence of myself and others who
do our best to impart any information we may
possess for the benefit of inquirers, that "G.'s"
classification of right and wrong seems on a parallel
with his knowledge. "Sm." is incorrect if his
statement be taken as representing the Admiralty
knot; but what he believed to be fact he freely gave.
A. Gadd is quite correct in his statement that the
Admiralty knot equals 1.151 miles. The explana-
tion of "J. T. M." is not unintelligible. My own
statement is correct, "G." notwithstanding. Then,
"G.," the seventh reply, is stated by our learned
critic to be correct. (Is that gentleman and our
critic the same person?) Yet "G." and myself
say exactly the same-viz., that the Admiralty
knot is 6,080ft. I regret to have to draw his atten-
tion to the fact, which will be awkward to explain
away, that he has to prove that out of two iden-
tical replies one is correct; the other, to use his
own statement, is incorrect. How does he propose
to justify this error into which he has fallen, yet
complacently decides who is and who is not right?
I certainly think an apology is due to the gentle-
men he has so incorrectly criticised. Vulcan.

MICRO-ORGANISMS.

[32571.]-I RECOMMEND every wise householder to read the new book on "Bacteria," in the "Contemporary Science Series." I send you a cutting from a North Country newspaper, very suggestive of "death in the pot."

above suspicion-viz., that in which the men (two) attempted to lift her from the ground. She drew a light knitted scarf or wrap over her shoulder and arms, and when so protected they could, sigly, lift her like a feather, as she weighed only 95lb. But the moment she removed the wrap and their hands came in contact with her bare arms, they could not budge her an inch, although they stooped down and with the palms of their hands under her elbows they lifted for all they were worth. Her shoulders merely raised a little; otherwise she seemed bolted to the floor. The men were, from the exertion, perspiring very freely: Mrs. Abbott was, apparently, quite cool. In another performance she held a stout stick, something like a billiard cue, only heavier, in her open hands, palms upwards, the left-hand wrist high and the right well above her head.

She now invited the gentlemen we selected to attempt to bear down on the stick until they could make the small end touch the floor. Twelve men, one after the other, tried and failed. Then they tried two at once without success, though they managed to break the stick-a good stout one of hickory. In all her lifting performances the doctors placed their hands between her hands and the chair or chairs on which the men sat, and they assured the audience that she exerted no pressure on the backs of their hands. Yet she lifted, upset, and sent sprawling over the platform eight men, packed like sardines on two chairs. I saw everything described by the Examiner, and as far as I can judge, the performance was genuine. If your correspondent cares to write to J. C. Black, Esq., Attorney-at-Law, San Jose, California, he can get that gentleman's testimony direct. Mr. Black was one of the gentlemen selected by the audience, and I am quite sure if there had been any trick in it, he would have exposed it. I should have replied to this query before, but I preferred to let someone better known than myself answer it if they would, as they apparently do not care to do. So I, at the risk of getting a scoring like the one I received st the hands of the late John Hampden, have attempted to describe what I actually saw. Your readers are at liberty to believe or reject it, as they please.

At the conclusion of the performance, Mrs. Abbott took a common tumbler, placed the bottom of it against her bosom, the open end towards the audience, and many of those nearest the stage declared that they could hear a noise as of something in rapid vibration. I admit I could not, though a friend who secured a seat much nearer the stage said that he heard it very distinctly, and the gentlemen and doctors on the stage said that the sound was very distinct, and, to them, inexplicable. Saml. Haigh.

Santa Clara, California, July 8.

"In 1803"-I quote from the "Guide dans Liége," by Dr. Fremder, now completely out of print, of which I was lucky enough to secure, I believe, the last copy extant-"a mechanician of Paris, called Périer, had taken an engagement to furnish for the armament of the flotilla of Boulogne" (intended for the invasion of England) "3,000 cannon of 36° (centimètres bore). He established his works at Liége, in the Faubourg Saint Léonard, on the foundation of an ancient priory dependent on the Abbey of St. Jacques. Two foundries were constructed for casting these guns, and six steam-engines of 96H.P. were established for the machine work." (One of these engines is still at the foundry.) "Périer could not fulfil the conditions of his bargain. The Consular Govern- "Since a wedding party was poisoned in Carlisle, ment" (in other words, Bonaparte) "had made there have been many similar fatalities on like him advances, and reimbursed itself by taking pos- occasions; so many, indeed, that Dr. Woodhead, in session of his works." (The italics are mine.) his new book on Bacteria' gives a chapter to a "Two naval officers, Petit and Jure, undertook, consideration of the occurrence of poisonings at one after the other, the last in 1807, the direction of feasts, festivals, and carousals generally. He sugthe establishment which, under the Consulate and the gests that at these gatherings the spirit of jollity Empire, rendered them great services, for they drew prevails rather too freely, producing indigestion, from it for the service of the French navy and gastric disturbance, and a lowered vitality, which coast batteries no less than 7,000 cannon of different are conditions very favourable to the operations of calibres." (No doubt some of these guns were used the deleterious bacilli. Then the food has probably by the French at the battle of Trafalgar). From been got in some days previously, and ancient re-hear of their using it at sea is about 300 A.D. One another very learned book, also extinct, "Histoire sources in the shape of cooking utensils may be des Liégois," by J. F. X. Wurth, Doctor of Philo-furbished up in the preparation of it. The bacillus, sophy and Letters at the University of Liége-but Dr. Woodhead finds, is almost invariably introlike all these aggravating French and Belgian duced by the mouth, and it is so prolific that, the books in paper covers, utterly without index or surroundings being favourable, a single germ, headings of pages for reference-I take the follow-visible only through the finest glass, had grown to ing:- Les 3 et 4 Août 1803, Bonaparte honora a mass which would weigh 7,500 tons! Green Liége de sa présence, et fit exposer par les magistrats stuff, where the water supply is tainted, is a de cette ville, les besoins du people, ses resources, frequent source of contamination. Dr. Koch son caractère, &c. Il consacra 300,000 francs à la describes the marketwomen of Marseilles as being reconstruction des habitations de Liége, que les in the habit of sprinkling the vegetables exposed for Autrichiens, en haine du dévouement des Liégeois sale with water from the street gutters, and thereby pour les Français, avaient brûlées dans leur supplying such of their customers as consume the retraite." The learned Dr. Wurth does not add if vegetables uncooked with a deadly dose of the Bonaparte ever paid this £12,000 which he told the cholera organism and its poisonous products." good people of Liége he had "consecrated" for the reconstruction of their ruined houses. I expect not; but even if he had, it would not have been a very cheap price for the thousands of cannon he had drawn from his foundry there, the works of which he had evidently come personally to inspect at this time in order to push on his invasion of England as rapidly as possible.

Eos.

"PHYSICAL" FORCE PHENOMENA.
[32572.]-SEVERAL weeks ago (letter 32279) one
of your correspondents asked for information about
an alleged exhibition of a mysterious power by a
young woman in San Francisco, an account of
which he saw in the S.F. Examiner. In San Jose
last April I saw a Mrs. Annie Abbott do all that
was stated in the Examiner, and several other acts
which Miss M. L. Price omitted from her programme.
I am personally acquainted with several of the
gentlemen selected by the audience to see fair play.
Most of these men were powerfully built, weighing
from 175lb. to 225lb. each, yet Mrs. Abbott threw
them about like children. Two of the most respect-
able medical men in San Jose examined Mrs. Abbott
for the audience, and reported that they could see
te about these foundry gates, which I nothing abnormal in her from a physical point of
ove-mentioned "Guide dans Liége," view.
ver, be omitted here. "The cele-

This foundry, kept up on a larger scale than ever, is now Royal, with His Majesty's (Leopold II.) arms, and two sentries, at its gates. I may, perhaps, in the suite of these letters, give your readers some account of its present performances, especially In connection with the new forts now nearly conted on the entirely novel designs of the celefficer of the Belgian Engineers, General but my present object is a description of l, not warlike, productions of the Liége.

One of her performances struck me as absolutely

THE MARINER'S COMPASS. difficult question. You could find an answer in 80 [32573.]-IN letter 32538" Metes" asks rather s the best. I should think an encyclopedia would many different books; but the difficulty is which is give you all the information you require. The Chinese annals, indeed, assign its discovery to the year 2634 B.C., when, they say, an instrument for indicating the south was constructed by the travelling by land. The earliest date of which we Emperor Hon-ang-ti. They at first used it for account says Marco Polo brought it to Europe on his return from his travels in Cathay. The com Flavio Gioja, a native of Almfi, about the year pass as a nautical instrument was invented by 1362, and that part of the kingdom of Naples had a compass for its arms; but for this there is not much authority. Gioja might have improved the instrument. I should also advise "Metes" to of the letter passes my understanding, and would see the British Annual for 1837. The latter part be, I think, rather hard to answer without reading

up several books.

C. G. M. Bennett.

[32574.]-As one who has for many years assiduously studied the theory of the Orientaliongin of sciences and civilisations, I wish to offer a few observations on the history of the mariner's compass. In regard to its Chinese origin, it may be pointed out that the Arabians have been the most skilful navigators among the Asiatics and Africans, and it seems there is no original word for the compass in Arabic, Turkish, or Persian, they generally made use of the Italian word for it, bussola, and there is no observation of ancient date made by the Arabians on the variation or use of the needle. The naval skill of the ancient Chinese does not apper to have been better than that of the Arabians, Greek, or Romans. In their voyages from Canton to the Persian Gulf they did not sail into the open sea, but followed the coast line. Sir John Chardin was of opinion that the Asiatics obtained the knowledge of the compass from Europe a long time before the Portuguese conquest.

It does not seem to be known exactly when the compass was first used in Europe. A passage has been adduced from a work of Raymond Suby,

published in 1272, which shows that he was ac-
quainted with the polarity of the needle, and thus
Flavio Gioia, the famous citizen of Amalphi about
the beginning of the 14th century, only improved the
compass. Macpherson's "Annals of Commerce,"
and Azuni's
Dissertation sur l'Origine de la
Boussole are considered good authorities. The
probability is that Columbus made use of the
compass in his voyage.

J. Skym.

A SELF-WINDING CLOCK.

nothing more or less than a strain on the molecules something, capable of determining with unfailing
or atoms, the result of a local force acting in oppo- accuracy the path having the least resistance
sition to the natural law of molecular attraction, a between a given point in the intended circuit and
simple vibratory motion set up among the atoms. its original source. If, as one of our eminent
One atom, with more or less force, according to the electricians says, it is a fluid of some sort, it must
power employed in producing the disturbance, necessarily have a head of flow; but he does not
strikes the next atom or adjoining atoms, and so on say by what means this head invariably selects the
throughout the entire circuit, both the N. and S. path of least resistance without ever having been
poles of the magnetic, if the wire on the armature that way before.
has been suitably placed thereon, forcing the atoms If in a circuit we have an indifferent connection,
in one direction. But before the first atom to be we find that it results in a considerable loss of
disturbed can move, owing to the density of the current-not locally at that point, however, but
conductor, all other atoms therein corresponding to throughout the entire circuit-simply because,
the limit of disturbance a given expenditure of unless the two ends of the wire are firmly united,
power will produce, must also be displaced through- the vibratory motion of the atoms would not
out the entire conductor, the first atom, or atoms, extend over a sufficient area at the point of con-
to move giving place to the last atom, or atoms, nection to communicate the full effect to the added
which temporarily occupy their places, and thus we length of wire the source of power was capable of
find that the period of time occupied by the current producing. If, however, the current be of high
in traversing a complete circuit is infinitesimal. It E. M. F., the force of the vibrations is sufficient to
may be that this atomic vibration takes place many project a number of the molecules forward towards
thousand times per second. In the case of the the end of the added length of wire, and these mole-
primary battery as a source of electrical disturb-cules, by being forcibly driven off, and by their rapid
motion through the atmosphere, become highly
heated, thereby forming an arc, and being either
wholly or partially vaporised. In the event of the
current being large, but with only a moderate pres-
sure, the atoms at the extreme end go over in a
body in a molten condition, and become attached
to the end of the badly-joined addition to the line.

[32575.]-IN your issue of the 24th inst. appears
a letter (p. 479) under the above heading, and as
your correspondent solicits your readers' opinions,
may I ask space to express mine, having devoted
two years to the identical system? The clock, as
above suggested, is open to many drawbacks.
First, a patent is still running, I believe, which
covers every system of clock-winding by motor;
but this does not say that you shall not wind by
electricity. Electrical winding is being done with-
out a motor, and bids fair to eclipse anything yet
attempted. Secondly, I have had one of the Self-ance, the vibratory motion of the molecules of the
Winding Clock Co.'s clocks in my possession for conductor is brought about by the violent disintegra-
some time; the best spell of going I could obtain tion of the metal constituting the positive element
from it was a month; by cleaning brake-pieces, by the action of the exciting fluid, which is
connector-wheel, and brushes, away again for again reacted on, thus communicating the vibra-
another month. This, to my mind, is the great tions to the negative element. If we have a circuit
drawback. Until a motor is constructed so as to of considerable length, or, to use an electrical
keep free from oxidising, motor-winding must be a term, of considerable resistance, we shall naturally It is, therefore, clear that electricity is not a fluid
failure. Thirdly, the vertical rod, as suggested, require more force or E.M.F. to impart a vibratory of any kind, and that it does not travel through the
would be unsightly with its projections, and neces- motion to the many millions of atoms that must dielectric, but through the conductor, in the form
sary pressure to close contact would have the necessarily vibrate before the current can be said and nature of atomic vibrations of inconceivable
effect of lightening the weight, reducing the pres- to overcome the resistance of the line. If, how-rapidity, in all cases taking the path offering least
sure on pallets, bring the pendulum under motion, ever, a path having less resistance, or containing a resistance for the reasons stated above, not con-
and consequently affect the timekeeping. Fourthly, smaller number of molecules, presents itself along fining itself to the centre or surface, and certainly
the differences between winding where weights are that path, the disturbance will naturally occur, in- not to the material constituting the insulation of the
the motive power, and a spring and barrel, are very asmuch as with superior disturbing force at the conductor. We shall, ere long, recognise that
great. In the case of the weight, some kind of source as compared with the resistance-naturally electricity and magnetism are one and the same
maintaining power must be found, as the escape- much less in the shorter path-operating against force, but merely manifesting themselves in a
wheel stands during winding. There is also just the this reduced resistance, the disturbing power is different form.
W. Laughton.
probability the wheel may go backwards, which I more than sufficient to overcome that resistance,
have seen. Maintaining power cannot be brought and naturally a greater number of atoms thus be-
into action with a much less driving-weight than come affected, the successive periods of vibration
21b., hence a powerful motor and battery, and becoming slightly shorter. Thus, expressed in
more oxidisation than you can treat with. A pro- electrical terms, we get more current and slightly
vision must also be made for gearing and ungearing increased voltage, varying according to the parti-
the motor or motor-train from the clock train, cular conditions under which it occurs.
whether connected by band, chain, or wheels and
pinions. In the case of spring and barrels, main-
taining power and gearing are dispensed with.
Even so, the cost of production will be found to be
against it in either methods, especially so since we
read letter 32416. However, there will shortly be
brought before the notice of the "E.M." readers a
clock that will compare favourably with that of
our eulogist for price and reliability.

G. W. A. F., E. C. M.

THE REAL NATURE OF THE ELECTRIC CURRENT. [32576.]-Ir is rather surprising to see that some of our most eminent electricians of to-day have the most unreasonable ideas as to what electricity really is, seeing that they have not only ample time, but means too, to study the subject in all its bearings. That anyone could possibly believe that it is a fluid-a foreign something produced by a battery or other source, and one that can be made to travel or flow through a solid metallic substance, is more than one can understand. Others, again, believe that it is a something having a path through the dielectric (!), and yet these latter theorists have not yet been able to successfully turn out a dynamo the armature and field magnets of which have been entirely wound either with silk or cotton thread. When this feat can be successfully accomplished, they will then have something to back them up in their strange belief. The "undulatory-motion' theorists are much nearer the mark; but this theory does not altogether account in a satisfactory manner for the behaviour of the current under varying conditions.

THE COST OF ELECTRIC LIGHTING. [32577.]-IN your issue of July 17 there is a letter (32523) signed by "A Mechanic," assigning as one of the reasons of the high cost of the electric light, that "in an electric-light station you will find any number of well-dressed men, nearly all of whom are quite above soiling their hands by doing anything so low as work." He also says, "The business is glutted with highly-educated electriciansmen who hold certificates from this school or that college-but give them a file or a hammer and it will take a large certificate for them to hide their

That the electric current is purely and simply a
vibratory motion of the molecules of which the
conductor is composed is clearly indicated in the
case of the induced current, which, as is well
known, is of an alternating character. On closing
the primary circuit, the molecules of the secondary
wire move in one direction, and then immediately
resume their original position again, so that, with-incompetency behind."
out further interruptions in the primary circuit,
there will be no other manifestation of disturbance
in the secondary circuit, although the current in the
primary circuit remains constant. On breaking the
primary circuit, however, we again find a tem-
porary movement of the atoms in the secondary as
before. This explains how the lines of force in a
magnet act upon the wires of the armature with
such tremendous effect, inasmuch as every atom of
which the magnet is composed, if separated from
every other atom, would still be an entire magnet
in itself, having N. and S. polarity; so probably the
lines of force passing between the poles, even if not
quite, are nearly, as numerous as the constituent
atoms of the magnet, and are, therefore, capable of
disturbing every atom in a given length of wire on
the armature, when such wire is suitably exposed
to their action, even to the extent of reducing it to
a molten condition. It is, therefore, clear that to
obtain this molecular disturbance the expenditure of
energy in another form is essential, because we see
that in the case of the induction coil, it is only at
the make and break in the primary circuit that any
disturbance takes place in the secondary.

A good illustration of this is the behaviour of a
body to which motion has been suddenly imparted
by some other body moving in the same direction.
The momentum of the body, after receiving the
I presume most people nowadays believe that first impulse, gradually increases until for a brief
everything in nature is composed of minute atoms. space of time it is travelling at a greater rate than
This granted, it will be the easier for me to explain that which first gave it motion. This is clearly
the undoubted nature of what is known as elec- indicated in the case of a cable passenger-car. The
tricity. In the first place, we have a metallic point at which it moves at the greatest rate is a few
substance-say copper-worked into the form of a yards in advance of the point where, when the car
wire. Now this wire is composed of an infinite was stationary, the gripper first closed on the
number of exceedingly minute atoms, or particles, travelling cable; but after this abnormal effect has
adhering to each other by virtue of molecular ceased, no further increase of speed as compared to
attraction, and so long as the temperature in which the rate at which the cable is moving can possibly
this wire (or of course any other particular form take place so long as the car moves as a result of
into which the metal may have been shaped) the hold of the gripper on the cable. To increase
may be placed does not exceed certain the speed over that of the cable (I have seen it
limit, it will maintain its original outline done, although it is not permitted), make and break
of form. To proceed a step further, we the hold on the cable at frequent intervals, and the
place this wire, which shall be of a suitable length car receives additional momentum at each grip,
and diameter, after the usual method on an arma- until a greater speed is obtained than that at which
ture, and bring it near to the poles of a magnet, and the cable is moving. In this we have a parallel to
on causing it to pass rapidly before the poles, the induction coil and its manner of working.
thereby cutting the magnetic lines of force, we find
that a certain disturbance is set up within the said
wire, provided (if the molecular resistance be suffi-
ciently low) the circuit is complete. The disturb-
ance thus set up, and which we term electricity, is

The theory that the electric current consists of a foreign something flowing through the wires or through the dielectric (this "subtle fluid," as it was anciently termed), is altogether too absurd, inasmuch as it presupposes it to be an intelligent

With regard to the first of his statements, he surely must have been unfortunate in his experience of electric-light stations. I have had to do with more than one where, for some length of time, the whole staff, with the exception of an engine-driver and a fireman, was composed of what I suppose "A Mechanic" would call well-dressed men." These individuals trimmed the lamps, kept the dynamos in order, attended to accumulators, and did the whole electrical work of the station, besides, at times, running the engines. I think this proves pretty conclusively that they were not above" soiling their hands" and their clothes too; and, as far as my experience goes, it points to the fact that the great majority of electricians are of this order. Of course (as someone has, I think, remarked before), there are exceptions to every rule; and perhaps "A Mechanic " is fond of hunting up rarities.

I agree with your correspondent that the supply of trained electricians is at present in excess of the demand; but, where they hold the certificate of a college or school, I believe they will be found competent to use both file and hammer as well as their brains. The training at some of these institutions, at any rate, has lately been given in as practical a form as possible, and ample opportunity is afforded to students to become proficient in the use of most of the tools to be found in the shops of a mechanical engineer with a good business. If they fail to take advantage of their opportunities, they also fail to take the certificate. A. I. E. E.

SEEING BY ELECTRICITY. [32578.)-RESPECTING the recent correspondence in your columns as to the possibility and probability of seeing by electricity, the following description of an instrument invented for the purpose may be of interest to your readers. I am surprised no one seems to have noticed it, as I believe it has appeared in the Times :—

"Our transmitter at A-that is, the apparatus for receiving the light impressions and transmitting them electrically-consisted of a large surface made up of very small separate squares of selenium. One end of each piece was connected by an insulated wire to the distant place, and the other end of each piece with the ground, in accordance with the plan commonly employed with telegraph instruments. The object whose image was to be sent by telegraph was illuminated very strongly, and by means of a

lens a very large image was thrown on the surface of the above transmitter. Now, it is well known if each little piece of selenium forms part of a circuit in which there is a constant electro-motive force, say, of a voltaic battery, the current passing through each piece will depend on its illumination Hence the strength of the electric current in each telegraph line would depend upon the illumination of its extremity. Our receiver at the other end, B, was, in our original plan, a collection of magnetic needles, the movement of each of which (as in the ordinary needle telegraph) was controlled by the electric current passing through the particular telegraph wire with which it was in connection. Each magnet, by its movement, closed or opened an aperture through which light passed to illuminate the back of a sheet of frosted glass. There were, of course, as many of the illuminated squares at B as of selenium squares at A, and it is quite evident that since the illumination of each receiving square depends on the strength of the current in its circuit, and this current again depends on the illumination

of the selenium at the other end of the wire, the image of a distant object might in this way be transmitted as a mosaic by electricity."

Such is the description of this instrument of which Messrs. Perry and Ayrton are, I believe, the proprietors. If this is practicable-and why not?the verdict of impossibility, passed by some of your correspondents, is rather hasty. July 25.

ELECTRICAL.

T. R.

[32579.]-I WILL endeavour to show, as clearly as possible, what I mean by the chemical action independent of lessening the resistance. If the size of the plate exposed to the liquid is increased, it will have a greater capacity, and will therefore hold more electricity. Thus, to bring both plates to the same potential, a greater quantity of electricty will flow, and, therefore, there will be more chemical action. Mr. Goodchild will notice that this increase of chemical action is not due to a decrease of resistance.

I have not performed the experiment I suggested, as I have not yet got every apparatus that would be required. I will, however, try the experiment as soon as possible.

In the experiment, I spoke of finding the resistance of the extra zinc. Instead of resistance I should have said conductivity.

I suppose when Mr. Goodchild says I contradicted myself, he means that first I said the chemical action is controlled by the resistance, and then I said that it is not. If he will read my last letter through carefully, he will find that he is mistaken. I used the sentence "which is not controlled by the resistance," not as a statement, but to point out which chemical action I meant, as I assumed there was more than one cause of the increase of chemical

action.

Amperes. Volts. Hours. Watt-hours. 14 x 24 x 30 = 10,080

structed to maintain a really continuous current 241b. depolariser salt, 2doz. reoxidising bags
for an indefinite space of time, the primary battery This becomes :—
might become of more practical assistance in
small electric-light installations; but hitherto no
such depolariser has been found, in fact we ques-
tion whether it can be found. Knowing this point,
the inventor of this battery thought perhaps it Or say 10 Board of Trade units (1 unit = 1,000
might be possible to construct a small form of re-watt-hours). 10 units at the above consumption
oxidising apparatus to go with the cell itself; but becomes :-
found that even when this was constructed it
would not, practically, work with any of the many
depolarisers on the market; so that an entirely new
depolariser had to be found that could be used with
the reoxidiser (i.e., a depolariser, that when it had
been reduced by the nascent hydrogen liberated in
the working of the cell could be reoxidised by a
stream of oxygen passed through it). A high
depolariser was at last found, and a battery con-
structed on this principle, which the following brief
description will help to explain.

The battery is of the single-fluid type, with
elements one carbon and zinc (Fig. 1). In this cell,

301b. zinc at 24d.

s. d. 57 0 114

24lb. depolariser at 5d.
2doz. reoxidising bags at 24d. doz. 0 5

6 114

unit. The cost of electrical energy generated by this method becomes 84d. per Board of Trade unit.

Taking this at 78. divided by 10 becomes 8jd. per

The reason of its great cheapness is because of the small quantity of depolariser practically used, the great cheapness of the reoxidising materials (being only 24d. per dozen bags); the depolariser is sold st 5d. per pound. The packed porous pots last from 6-9 months. There is no smell or fumes, neither is there any action on open circuit.

The terminal connections of the elements do not become corroded or eaten away. The chief festare of the battery is not the depolariser, but the reoxidising apparatus, though, as before statai, the depolariser is a special mixture.

Knowing what puffs have been written and printed about many former batteries brought out, it is the desire of the inventor of this battery the: all, before having a set of these batteries, should practically try a small sample cell (sample cells are being made specially for this purpose).

Trusting we may be excused for trespassing on so much valuable space, we shall be most willing to answer any and all queries in respect to same. Clark and Montigue (Sole Agenta).

LOCUSTS IN ALGERIA. [32581.]-ALGERIA must be a lively place to live in, and I should like to know whether our friend "Eos" has had any experience there. I sent you last week (p. 479) an extract from a letter published by the editor of Horse and Hound, and here is another bit which he gave to the world in his iss of July 25:

at A, is a porous tube, very closely packed with "The locusts are still inside and outside my vine lump depolariser; this tube also has a perforated If I open my barrier of zinc and let out the small bottom, B, in the upper part of this porous tube. ones, the big ones come in. If I don't let the small C is the glass reoxidising apparatus, and consists, ones out, they eat the vine little by little. I tear as shown, of a glass tube with side outlet tube, and that it is all up, and that complete ruin is imminent. provided also with a glass stopper. The side tube However, I struggle on, but really am most unfor goes down into the packed depolariser. A more tunate. For more than a fortnight the large locusts detailed drawing of this is shown in Fig. 2, where have been in the habit of settling every night in the A is an outer tube with stopper and outlet tube. jujubiers of a neighbour, and every morning regu In this outer one slides an inner and shorter one, B, larly they endeavour to force an entrance into my which is also provided with a small glass handle, vine, and I have to keep fourteen men on that side I would remind Mr. Goodchild that a circuit con-X, to pull it out and empty it by. This inner tube alone. The neighbourhood has about-or, rather, sists of two plates and the liquid (which has a great is rendered requisite, as the outer one with outlet had about-ninety small haystacks close to the resistance), besides the external circuit. Are these tube is a permanent fixture, and sealed in the jujubiers, and we had told them a dozen times to negligible as well? I think not. Not even if a porous tube with a special cement, and also for take them away, so that we could burn up the person wished to make them so. The zinc is only a being more handy to empty the reoxidising chemicals locusts. On Thursday, when I was at the far end small part of the resistance of a circuit, and if the away when used (as further explained). of the vine, with a sirocco blowing, and the therpart exposed to the liquid is doubled, only a small To use this cell, one or two ounces of the de-mometer at 37° C. (98° Fahr.) indoors, my man part of the resistance is halved. In speaking of the polariser salt is put in the cell and filled up with proceeds to set fire to the jujubiers. Naturally the electric battery, I take the simple cell as a type, for water, and allowed to stand for a few minutes, stacks catch fire, and in twenty minutes forty-thre sake of simplicity. Did Mr. Goodchild refer to the when it is ready for use. The voltage of each cell stacks are in cinders, also thirty-eight olive-trees, bichromate cell when he said lengthening the zinc being 2 volts (being the same as the ordinary also three other large stacks belonging to our next plate decreased the resistance? If so, he is quite chromic acid), and the current strength averaging door neighbour. One hundred and fifty Arabs ware right. I referred to the simple cell where lengthen- from 4 to 30 ampères (according to size), with the soon at work beating out the fire with branches of ing the zinc plate, it is evident, will not expose small sample cell, this strength is constant for six trees, and thirty Zouaves assisted. As soon as I more surface. It is simply a difference of mechanical to eight hours, when the depolariser will require saw the flames I rushed home, and fortunately had arrangement. reoxidising. To do this, a small reoxidising bag is three hogsheads of water ready, and the Zouaves, put in the glass tube, with the addition of a little running down from the village, helped me to har water, and the tube again closed. Immediately a ness my waggon and gallop off with the water across chemical action is started, whereby oxygen is dis- the beastly lumpy fields to the fire. We just engaged. This immediately passes through the managed to put it out when it was going into outlet tube into the depolariser, reoxidising that, forest of olive-trees. The gallop over the rough which has been reduced by the nascent hydrogen ground, carrying 800 quarts of water and four liberated in the working of the cell. This imme- Zouaves, has nearly killed me. The fearful bumpdiately renders the cell to a suitable condition for ing has left no skin on the place where the skin another 6-8 hours run. It is possible, on this ought to grow; all the loss falls on me, and, as you principle, to construct cells up to a total 100 hours can imagine, this is the last straw. The heat in constant with one charge. The solution requires town is also intense; the worst of it is that it is a to be changed every 20-100 hours (according to moist heat, which is so depressing. Also mosquitoes size cell), not because the depolariser and excitant galore.' become exhausted, but from the simple fact of the solution becoming too saturated or clogged with the zinc salt.

Although, assuming that electric force cannot exist without resistance does away with one objection, it brings up another. I said the mathematical treatment of Ohm's law is defective, and the following is an example:-If force cannot exist without resistance, there must be a certain amount of resistance before the force can exist. We find this amount of resistance by Ohm's law to be one ohm, since one ohm is just sufficient resistance to keep up the force from beginning to end without diminishing. Less resistance than this certain quantity would not allow the current to pass, and yet less resistance increases the current's strength. If by decreasing resistance below unity raises the current's strength above the E.M.F., and it is found to be so by experiment, there should be some other explanation for it than Ohm's law.

A. Benjamin.

THE OSBO-PREMIER BATTERY.

The reoxidising bag consists of a special mixture of chloride of lime, with a few crystals of nitrate of nickel. This, in the presence of moisture or water, generates oxygen. This generation of oxygen takes place more quickly if the solution is [32580.]-So many of " ours are so constantly warm (however, this not absolutely requisite); but asking for a reliable form of primary battery that from the chemical action taking place, this is more perhaps a description of a new form of battery now or less provided for, as the solution is always above being placed on the market (for which we are sole the temperature of the surrounding air. agents) may not be without interest, as this form is As regards to the cost of running, the cell comnow being designed and manufactured on an en-petes with all others at present known. A set of 12 tirely new and different principle to any hitherto cells, measuring 24in. by 18in. by 10in., and weigh brought out. ing 15lb., gives 14 amperes at 24 volts constant for It is well known to all electricians that if a 30 hours with one charge (3oz. depolariser per cell thoroughly serviceable depolariser could be con-added) at the following consumption: 301b. zinc,

It strikes me that, "after all," England is not such a dreadful place to live in.

Nemo.

Action of Nitric Acid at Different Strengths and Temperatures upon Iron In Comptes Rendus, Henri Gautier and G. Charpy state that nitric acid attacks iron at every degree of concentration, but the action may take place in two different ways-the one rapid and attended with an escape of gas, and the other slow and without a production of gas. The existence of these two modes of action explains very simply the pheno menon known as the passivity of iron, which corresponde not, as it has been hitherto supposed, to the absence of all action, but merely to a slow action without the liberation of gas.