his firm have made, and are making, the consumption is reduced to below 1.71b. per H.P. per hour. He thinks that as still higher pressures are adopted greater economy will be obtained; but the question is, can much higher pressures be used with safety in marine boilers?

LETTERS TO THE EDITOR.

[We do not hold ourselves responsible for the opinions of
ommunications should be drawn up as briefly cs possible.]
our correspondents. The Editor respectfully requests that all
All communications should be addressed to the EDITOв of
ENGLISH MECHANIO, 332, Strand, W.O.
All Cheques and Post-office Orders to be made payable u
J. PASSMORE EDWARDS.

In order to facilitate reference, Oorrespondents, when
speaking of any letter previously inserted, will oblige by
mentioning the number of the Letter, as well as the page on

which it appears.

The opening meeting of the Internationale Congress of Hygiene and Demography will be held on Monday, August 10, and the medical and scientific sections will afterwards meet in the rooms at Burlington House, the division of Demography being held in the School of Mines, Jermyn-street. It is expected that there will be a large attendance of those interested in the subjects which include architecture and engineering. At a recent meeting of the Scottish Microscopical Society, Dr. H. J. Stiles read a paper on theDevelopment of the Mammary Gland," in which he gave the results of investigations of its development in the human subject, the calf, pig, dog, rabbit, and other animals, which had convinced him that the secreting acini of the gland are developed from the epiblast, as Kölliker long ago stated, but which Dr. Creighton had endeavoured to disprove.

At the same meeting Dr. W. H. Barret demonstrated new methods of handling paraffin sections, and Mr. Ballantine exhibited a new photomicrographic camera made to a design by the late Mr. Schultze, which will attract much attention amongst photographers of minute objects.

M. Olszewski says it is a mistake to suppose that liquid oxygen is colourless; when examined in a layer about lin. thick, it has a bright blue colour, and he thinks the blue colour of the sky is due to atmospheric oxygen. His most interesting fact is that in the absorption spectrum of liquid oxygen, one of the five bands it contains is coincident with Fraunhofer's A. The blue colour of liquid oxygen may, however, be due to the same cause as the blue colour of pure water.

should remember.

It is said that probably one of the largest and richest veins of tin ever known to the mining world has been discovered in the old Diablo Mine south of Durango, in Mexico. The vein is 4ft. wide, and composed of solid masses of tin oxide, assaying from 50 to 60 per cent. of tin.

much as he knows, but no more; and that not in this
"I would have everyone write what he knows, and as
only, but in all other subjects: For such a person may
have some particular knowledge and experience of the
nature of such a person or such a fountain, that as to
other things, knows no more than what everybody does,
and yet, to keep a clutter with this little pittance of his,
will undertake to write the whole body of physicks, a vie
from whence great inconveniences derive their original."
-Montaigne's Essays.

THE

WEATHER WHYS? OR OTHERWISE
GEOLOGICAL : THE DARTFORD
HEATH GRAVELS-VIRGINIAN CON-
TINUATION OF THE BONN "DUROH-
MUSTERUNG " VARIABLE STARS
OF LONG PERIOD — THE DRAPER
CATALOGUE OF STELLAR SPECTRA
-HARVARD PHOTOMETRY-ORIEN-
TATION OF THE PYRAMIDS-THE
PLEIADES AND THE MILKY WAY-
HOW THE PLANETS MIGHT NOT
BE OBSERVED TIME

OF SUN
SOUTHING, &c.-METEOR RADIANTS
-POISONING CATS-IN VINO MEN-
DACIUM-TELESCOPIC WORK FOR
STARLIGHT EVENINGS-THE GHOST
OF THE MAGNESIUM FLUTING-THE
MOON'S AXIAL ROTATION-SOLAR
THEORY.

[32355.]-I CAN only express a hope that some of
my brother-readers obtained a better view of the
transit of Mercury during the early morning of the
10th instant than I did. I got up at 4h. a.m.
G.M.T., and returned to bed, punctually, at
It is scarcely necessary to add

4h. Om. 45s. a.m.
more.

rain (never occurred at all), also about the 16th (if
possible, a worse shot still, barometer unreduced to
sea-level 30-351in. !) a deep depression round the
3rd, with rain (worse and worse). Fog often.
between the 10th and 27th." (Mist on the 18th
and 19th for a short time; dense fog on the 21st, in
the morning, but a brilliant afternoon, evening, and
night; 23rd again foggy in the morning, brilliant
afterwards. These are, so far, the best shots the
learned author has made-"and that isn't saying
much.") MARCH was to be "a dry month" (I
had 2.42in. of rain) with "fairly high readings"
of the barometer". except during the first few
days. (Oddly, for the first few days, the barometer
9th; below 29in. on the 10th and 11th, was again
did read high here, but went low on the 8th and
low on the 16th, &c.)" A fine week round the 28th
(my radiation thermometer read 15 F. during the
early morning of the 22nd). Boisterous round the
7th (heavy snow and gale on 8th and 9th-another
fairly lucky fluke). Frosty during last half of
month (again approximately true). APRIL was to
be "a wet and stormy month" (it was the very
driest April I have ever recorded, for only 0.39in, of
A cold and backward spring (right
rain fell).
as the play bills say, "positively for this occasion
only"). Snow about the 1st and 30th (certainly
not)-but need I pursue this? This precious
"weather chart" is as wofully astray about the
temperature, the barometric pressure, and the rain
of April, as it is in its other items. Now I would
merely ask such of my brother-subscribers as
keep meteorological registers, to compare them
with the predictions which I have copied verbatim;
and then ask themselves what must be the intel-
lectual calibre of the people likely to be taken in by
such a type of pseudo-science as this?

Since writing paragraph twelve of letter 32316, p. 248, I have come across an important paper by Prof. Prestwich in the Quarterly Journal of the Geological Society for the current month, "On the Age, Formation, and Drift-stages of the Darent Valley." Incidentally, Dr. Prestwich deals with the Dartford Heath gravels, which he regards as belonging to the later Glacial age. "RY." (query 74352, p. 212) should obtain and read this instructive essay for himself.

The observations begun at Cincinnati by Prof. Ormond Stone in continuation of the Bonn "Durchmusterung" have been carried on by him since his appointment as director of the Leander McCormick Observatory of the University of Virginia, and that institution has now issued the results in the shape of a catalogue of 6,671 stars between the 5 8th and the 10th magnitudes comprisod between 23 and 24° South Declination. Prof. Stone, in his preface, gives an account of the method of observation, and of the precautions taken to insure great accuracy and, taking the latter for granted, has produced a valuable work of reference.

Referring to the paragraph on p. 272 as to the explosibility of permanganate of potash and glycerine, Mr. T. B. Russell says in the Lancet that a friend of his told him some years ago that when preparing a prescription in which those substances were to be used, an explosion followed. The explanation, he says, is simple. Danger with permanganate and glycerine arises from the I have just got hold of some most remarkable same cause as that attending the admixture of nonsense in the shape of "The British Weather nitric acid and glycerine. Both permanganate of Chart, 1891." I forbear from any mention of the potash and nitric acid are powerful oxidising author's name, inasmuch as he writes" F.R.A.S."! agents, and the chemical affinity of glycerine for after it, and I am, just to say, dubious as to the Another work, of greatest value to variable-star oxygen causes the two to work with so much amount of credit conferred on the Royal Astro-observers reaches me too from America. It is by energy as to produce heat and (under favourable nomical Society by his most recent performance. that admirable and typical astronomer, Prof. E. C. circumstances) explosion. The same terms would Imprimis, he resuscitates then times exploded notion Pickering, of Harvard, and is devoted to "Variable constitute an explanation in chemical language of that "the moon has a great deal to do with the Stars of Long Periods." It is of an eminently the explosion of gunpowder, wherein the salt-production of the weather." "The perturbations practical character, as will be seen when I say that petre (KNO,) is the oxidising agent. Per- of the sun, moon, and planets" also come in, and it gives a list of 17 of such stars, all being circum. manganates, being unstable, are always rather fluences, an effect is assumed to be produced both duration; and, dealing subsequently with each in from this combination of astro-meteorological in- polar, and having periods of one or two years in liable to produce rapid oxidation, as prescribers upon terrestrial atmospheric temperature and detail, gives a little catalogue of some five-and-twenty pressure. Nothing would be easier than to show stars in its immediate neighbourhood, of all magnihow utterly fallacious such a system must be; but tudes visible, in a 6in. telescope, for comparison, "Ars probat artificem"; "the proof of the pudding addition to a chart of the region. The observer is is in the eating"; and "by their fruits ye shall know thus supplied with a series of objects of reference, them"; so I will simply take the author's predictions with which he may compare his chosen star through and compare them with the actual records made for comparison with those made at Cambridge for the four completed months of the present year, all its phases. Prof. Pickering invites observations by myself at the station whence I write. "JANUARY, (U.S.) a dry and cold month (2.90in. of rain here, cold unquestionable). A high barometer until the 11th (barometer reduced to a temperature of 32° Fahr. on 12th at 9h. a.m. 30-342in., at 9h. p.m. 30-282in. On the 13th at 9h. a.m. 30-292; at 9h. p.m. 30-244in.; on the 14th, at the same hours, 30-250in. and 30-226 respectively; on the 15th, 30-160in. and 29.926in., and so on. These are not reduced to sea-level, which would give much higher readings, the cistern of my barometer being some 250ft. above the sea-level). Then two depressions, one on the 13th and the other on the 19th (the 13th is effectually Electric drills for mining purposes are re-disposed of above. On the 19th, at 9a.m., the placing compressed-air drills in some parts of barometer, reduced to 32° Fahr., was 29-910; at the United States. 9h. p.m. 29.985). A steady rise sets in; very high barometer at the close (29-742, 29-728, &c., here). Boisterous weather, with perhaps thunder and hail, INDIARUBBER brake blocks have great advantages about the 13th (a pretty rapid thaw here), snow over those of wood or iron for road vehicles; but about the 6th, 14th, and 20th (really on the 7th, hitherto great difficulty has been experienced in 15th, and 19th in small quantities). Fogs about the fixing them to the shoe, owing to the rubber be- 18th (most brilliantly sunny) and 22nd (cloudy, I must confess that the third paragraph of your coming disintegrated where the bolts pass. M. with wet, sleet, &c., but no fog whatever). An "Scientific News," on p. 247, is a hopeless puzzle Michelin et Cie., of Clermont Ferrand, get over easterly gale about the 19th (this really did come, to me. What Herr Nissen and Mr. Norman the difficulty by forming the rubber block with a but a day too soon). "FEBRUARY," was, according Lockyer may have discovered (or imagined they dove-tail at the back and making the shoe to cor- to our author, to be "a dry month." He predicts have discovered) as to the orientation of Egyptian respond, both being slightly tapered so as to permit "about an inch of rain, chiefly early in the month" buildings I do not know, not having had the adof easy introduction. The rubber block is inserted (but, perversely, not a drop fell throughout the 28 vantage of perusing their statements on this subject in its shoe with an easy fit, and the tightening of days of which it was made up). His "high but if there be one thing more certain than another the block on the wheel spreads the dovetail out barometer during the last half of the month it is that the late Mr. R. A. Proctor not only insisted against the sides of the shoe, giving all the neces- (really extended from the first day of it to the last). that the Great Pyramid was "orientated on an sary adhesion between the two surfaces. A moderate depression about the 9th, with some astronomical basis," but pointed out by what purely

The output from the coal-mines of India is gradually increasing, as the amount "banked" in 1890 was over two million tons, or an increment of 11 per cent. as compared with the output of the previous year.

A trial of a writing telegraph was made recently between Pittsburg and New York, and the result was considered fairly satisfactory. It was found, however, that the machine must be placed on a very firm basis.

I must furthermore mention another splendid contribution to science in the shape of the Draper Catalogue of Stellar Spectra, photographed with the Sin. Bache telescope, which forms Vol. XXVII. of the "Annals" of the Harvard College Observatory, and gives the places for 1,900 of no less than 10,498 objects whose spectra have been photographed and measured, with details of their respective types of spectra and copious notes. This grand work must always form a standard of reference for the Stellar Spectroscopist.

Before finally dismissing the recent volumes issued from Harvard, I would urge Mr. Clapham (let. 32285 p. 206) to obtain and read Part I. of Vol. XXIII. of the "Annals," which contains an exhaustive discussion of the observations made with the Meridian Photometer during the years 1882-88. He can scarcely fail to be impressed by the evidence which it contains of the elaborate precautions taken to prevent and eliminate error.

I hope that "J. H." (query 74478, p. 257) doesn't keep an inn or restaurant. If so, he ought to give his address-that his brother readers may avoid it! Since the appearance of Webb's" Celestial Objects for Common Telescopes," I much doubt if any work more useful to the amateur observer (and notably to the beginner) has appeared than "Telescopic Work for Starlight Evenings," by that well-known astronomer, and occasional contributor The above is from a drawing made at 10.45 p.m., to these columns, Mr. W. F. Denning. One con- May 4th, at the telescope, Browning, 104in. With spicuous merit of Mr. Denning's excellent book lies mirror, power 208. Weather very clear, though in the fact that it is obviously written by a man barometer falling for heavy rain; seeing superb, at possessing the most thorough personal familiarity instants magnificently so; seven satellites, two as with the objects which he so lucidly describes, and merest points of light near ring, distinctly visible, that his instructions are based upon his own even with lower powers, including Kellner eyepractical knowledge of the subjects on which piece, power 86; anterior portion of ring roughened he treats, alike of instruments and of the ob- along edge, or surface, and intensely black, no jects observable by their aid. In these days, illumination; Ball's division not perceptible anywhen (so-called) "astronomical" books are, but where; belt on southern hemisphere of planet well too largely, compiled by the aid of a pair of marked; ball yellow, and very bright between belt scissors and a paste - pot, such results of the and ring; anse ruddier in colour than planet, no writer's own experience as those given to the doubt about this, all powers showing difference. world by Mr. Denning in the book before me Observation made interesting by reading Professor become doubly valuable, and especially is this Trouvellot's article (being published on this side of true in the case of such subjects as comet-seeking Atlantic) respecting long series of observations in and meteoric observations, in which he is facile 1877-8. That observer accounts for intense blackprinceps in this country. To anyone who has be-ness of anterior portion of ring, at this phase, by come the recent possessor of an astronomical telescope, or who is contemplating the purchase of such an instrument, I would say, Buy "Telescopic Work for Starlight Evenings" straightway.

supposing existence, near centre of ring B, of "protuberant zone,' casting deep shadow ringwards, and sufficiently thick (500 miles) to quench any oblique solar rays that otherwise would illu

moves round the table, keeping his face always looking towards the object, he will find that when he arrives at that part of the table directly opposite to where he set out, he will be looking at the other or opposite side of the room. To do this he must have changed his front; in fact, has turned himself half way round. Let him proceed so until he reaches his original position, he will then again be looking at the same side of the room as he did when he set out. From this I think "Mitchell" will understand that he has turned himself entirely round. No doubt his axis has not been fixed any more than the moon's has; nevertheless, this does not alter the fact that he has turned completely

round, or rotated once.

Ecnal.

THE MOON'S AXIAL REVOLUTION. [32360.]-IF "Mitchell" will procure Mr. Norman Lockyer's "Astronomy Primer," 18., he will find his question dealt with in the chapter on the Moon. As far as my memory serves, the example is to take a pole and place upright in the ground, place the hands upon it and walk round it, keeping your face towards the pole. When you have passed round once you will have made one revolution round the pole, and your head will have rotated also, as you will find out if you keep on moving round the pole, probably becoming dizzy.

I have seen the same suggestion in some other astronomical books, the mast of a ship being substituted for the pole in ground. This is the most simple explanation I have met with as to the manner in which the moon's revolution round the earth and her axial rotation can be so coincident that the same side of her surface is always earthReigate.

ward.

W. Paxton Thorp.

[32361.] Is this question asked seriously, or is it a joke? Surely they must be a funny kind of schoolmen who could not demonstrate this simple fact. Take an orange, and stick in one side thereof a big pin. Hold the orange at arm's length, so that the pin is on the side remote from you, and faces (say) north. Imagine yourself the earth and that the orange is the moon. Now rotate yourself upon your major axis, so that you make a complete circle, facing alternately E.S.W. back to N. The pin on the orange will also have "boxed the compass" in a similar manner, and therefore it is obvious that the orange has made a complete revolution upon its Sm.

own axis.

and round, the skin of his finger will be of the most
abnormal construction if it fails within a few
minutes to convince him once and for all that the
moon does rotate on her axis once for each revolu-
tion round the earth.
Charles D. P. Davies.

the last two articles on above, and signify my wish
that the drawings of American watch-lathe, so
[32365.]-I DESIRE to express my appreciation of
kindly offered in the last, be accepted for publi-

cation.

Would it be asking too much to ask the author his self-acting cross-feed, and self-acting and of previous article to explain and give sketches of traversing by-rack. The drawings of swivellingspindle show it partly, but not quite clear enough.

D. G. T.

have been interested in the articles under the above
[32366.]-MAY I be allowed to say how much I
title. They are just what I have been wishing to
"Mechanicus" deserted us some five years ago.
see in the "E.M." for a long while; ever since
May 15th, is especially interesting. How difficult
it must be to get the shape of those formers just
The article on Cutters, &c., in the number for
right, and how much easier it would seem to be
to make the other kind of cutter, which only needs
to be turned to the correct shape at the edge, and
then sawn across.
made will act fairly well, or are they only fit for
Do I understand that cutters so

use on brass.

MAY 29, 1891.

than your mill, you cannot fail to get a tooth to fit as correctly as you have made your template to fit. pin O a fixed size, and so much smaller than the It seems to me that instead of having the guidecutter, if it was made to act as an arbor for a set of rollers, turned to suit the different cutters, it would be found a more convenient and better arrangement.

What success I may have with the arrangement I the amount of work on it is less than on "M.'""" am at present occupied with I do not yet know, but strikes me, however, as very top-heavy for so light As to his planer or shaping attachment, it interests me less, as I have no need for such a fixture. It connecting-rod to the saddle does not seem the best a bed, while the position for the attachment of the position of the poppet-head, which, I suppose, it is possible; but it may be rendered necessary by the intended should be between the shaper head and

the saddle.

In the Y-shaped bed I recognise one of the forms an old correspondent. If this be so, and he is still prepared some years ago, when the front-slide lathe recognised in "M." not only an old subscriber, but interested in that now nearly forgotten subject, if bed was under discussion, and I have thought I he cares to write to me I should be glad to lay have many conveniences which are absent from the present. given up the hope that the lathe of the future will before him my latest ideas, for I have by no means

coning out the holes for the geared spindles? I have adopted his angle of 12°, and made two guideMay I ask "M." if he found any difficulty in teeth I put 20. In the first one, the two cones were bits to the pattern he gave, only that instead of 5 broke it in trying to bend it straight. The second made in one piece; and as it cast in hardening, I mounted on a turned arbor. This I first tried to one I made as separate collars, hardened and drive with a wooden pulley from the overhead, but could not get power enough. I then mounted in chuck, and after I had bored within fin. of the 45° cone, I could not force it in any further. I then turned out of flat steel a borer to the correct cones, lagging it with hard-wood on each side. With this I

I do hope the details of the American watch are beautiful little things, but very expensive, as lathe will be published. Those spring wire chucks they have no range, being intended only for one size of wire, therefore a great many must be kept. I made two or three Essex chuck springs, with a range of in., by turning the coned part when under compression. This made them nearly true. I think in., is enough range, and they should be made of tool steel; thus they need not be hardened, and you could do with eight of them. The short blunt cone and parallel bore of the hollow spindle on page 261, though very nice for the split-wire chucks, is rather awkward to combine with the Morse taper. I understand the taper fitting in watch-lathe mandrels is being given up, and the [32362.]--"MITCHELL" (32342) has reason to be shoulders, just like the wire chucks. How would centres fitted with a parallel shank and coned dissatisfied with the account of the axial revolutions hold arbors for milling cutters? How very care- I of the moon as usually given in astronomical text-fully the fit must be made to avoid all shake of the this do for larger lathes where you want to books, inasmuch as they involve a seeming paradox, centres! And the tail-pin and cross-head to take and yet he is wrong in supposing that the moon the back thrust of mandrel must be quite given up does not rotate on her own axis. It is very certain if we are to adopt the drawing-in spindle. These that, in relation to the sun, the moon makes about are the considerations which led me to try the 13 rotations a year; but her relation to the earth is a matter upon which there is room for discussion. The usual explanation is that the moon must described, which I have in use, and still wonder screw-ferrule plan with bayonet fitting, formerly rotate on her own axis once in about 28 days, because she always presents the same face to the whether it may not be better than the drawing-in earth. But here a curious paradox comes in, for, spindle. on the same principle, a ship at her moorings must rotate on her own axis once in 24 hours, because she always presents the same face-her keel to the

earth.

Again, if a circle be chalked on the rim of a flywheel, it may be asserted that the chalked circle revolves on its own axis with every revolution of the flywheel. Nay, more, if the circle so revolves, then every atom of the flywheel must revolve on its own axis, and if this be the case, the matter of the flywheel must be a liquid. From this it would appear that a statement may be mathematically correct, and yet be physically false.

tried more than once to draw your readers on the
It would indeed be a good thing if we had a
"properly tabulated system of tapers." I have
subject. I think, for instance, the locomotive
engineers might give us the proper angle used for
the lathe-makers the angles used for centres, mandrel
piston-rod ends, cottars, bolts to be driven, &c.;
collars, &c., tapers for plugs of cocks, &c., and, in
could draw up a table in inches per foot, and in
short, all kinds, whether coned or flat, then "M."
degrees and minutes. Afterwards we might have
the tools for measuring tapers.

pinching-screw apply equally against the little inBy the way, do not the arguments against the There is evidently a hitch somewhere, and I, like ternal pin which keeps the wire chucks from turn"Mitchell," shall be curious to see how the mathe-ing? Both will interfere slightly with the cleaning. maticians will deal with the paradox. If they leave it alone, their explanation must remain unsatisfactory. Ja. Ha.

[32363.]-I THINK the difficulty will be removed by taking into consideration the following:If a body travels round a centre but does not rotate on its axis, each point on such body will face, so to speak, parallel to one direction; and to enable any one point to continue to face the centre of revolution, and so, in turn, face all directions in a plane, the body must be twisted on its axis. Very little investigation (experimental or otherwise) will clearly show that it is impossible to rotate a body in the same time as a revolution, and not keep one point facing the centre round which the body travels. May 25.

A. Gadd.

THE MOON'S AXIAL REVOLUTION-
OR, MORE PROPERLY, ROTATION.
[32364.]-IF "Mitchell" (33342, p. 273) will tie
a stone to one end of a piece of string, making at
the other end a loop into which his finger will go
quite easily, and will then swing the stone round

F. A. M.

[32367.]-I DESIRE to thank "M." for his last which I have no doubt would work effectively interesting article on "Cutter-Making Machine," limited by the spindle being capable of carrying a within its range; but that it seems to me is seriously cutter only between the bearings. Thus mounted, it will, indeed, make such cutters as Fig. 8 or 12; but Figs. 9, 10, 14, as made by it, could have no clearance given them, and I would expect them to am at present busy making a machine, which also work very heavily, owing to friction on the sides. I works on the spring plan, and with which I hope to be able to make all kinds of cutters, and at same time secure clearance all round, as "M." says the American ones have.

I notice also that in forming his formers, or templates, he takes not the outside or tooth curve, but the bottom of the serration, as I proposed to do myself, but of which "D. G. T." showed me the at as the outer one. Besides, if you have a parinadvisability. It is a curve not so easily arrived ticular wheel to fit, it is a comparatively easy matter to fit your template to the wheel teeth, and then, with a guide roller two depths of cut smaller

completed the boring of the two ends; but it was very slow and hard work. My cones are in. at smaller end, and 1in. at larger, being 12in. long.

cones of this size in cast iron, I had far rather fit steel collars to cylindrical holes in the castings. I If there is not some easier method of drilling out have been told-on authority which few would combined with a cone of 45°, 1° ought to be suffi think of questioning, and which I do not-that, don't think I should ever again use so large an angle as 6°. I did so on this occasion because I cient for the long cones-that is, a total angle of 2o. thought it well to allow somewhat extra for wear. thought the usual allowance for hardened bearings was 1°, making a total of 3° for the cone. was using ordinary cast iron for my bearing, and

I

Fredk. Carre.

fifteen years, and I don't think it was ever better
LATHE MATTERS.
having! I have read the "E. M." for the last
[32368.]-WHAT a "good time"
than now.
we turners are

A

relative size the wheel and pinion should be, and also
articles
The Geared Driller.-Would the writer of the
what pitch he recommends? Would he also increase
on "Lathe Appliances "
the details of how to fit a split chuck to his hollow
tell us what
our already great obligation to him by giving us
spindle driller, so that it will hold truly drills of

various sizes.

this correspondent give us some further particulars
of his method of dividing the circle (mentioned and
Dividing Apparatus.-To "Valcan."-Would
figured in Vol. XLV. p. 60) by means of cylinders
and evolutes. I have always read "Vulcan's"
letters with great interest; but not being so well up
in following him, and in this particular instance I
in his subjects as he is, I often have great difficulty
would give me a helping hand?
can't make him out at all. Perhaps "F. A. M."
A. H. S.

PARALLEL v. BALL BEARINGS FOR
CYCLES.

a

by a mathematician. In my opinion, ball bearings [32369.1-I SHOULD like to see this point argued bearings are only suitable when the moving parts are a mistake for cycles. So-called anti-friction are of extreme lightness, such as, for instance, the mechanism of an Attwood's machine. It is a common thing for an "argument" in favour of ball wheel will continue to rotate when the machine bearings to be based upon the length of time the is forcibly by means of the treadle; but that is suspended and a fallacy, because the only weight is thate of the the wheel is matters are changed. Take, as an example, turned wheel itself. When a rider is on the machine modern tall bicycle, in which the majoritys of the weight is carried by the front wheel. The weight on the axle is supported by, at most, four balls, two

on each side, and since the balls touch the axle, the have been subjected to magnetic treatment, and I
seating, and each other at points only, there is no have seen cases that have been cured by the treat-
surface to hold oil, and the friction is increased ment.
inversely as the amount of surface exposed. It is I can assure Mr. Smith that cases I have met
true that some of the weight is taken up by lateral with before treatment were not those of "nerve
thrust; but this introduces more friction. The use mimicry, paralysis, and stiffness of joints," unless
of balls does not do away with sliding friction. this mimicry can go so far as to thicken the joints
According to my experience, ball bearings wear out with an external layer of hard matter. Such cases
very quickly, and it requires an expert to repair or would scarcely be "liable to recovery from any
renew them, whereas anyone can adjust the old strong mental or physical impression " produced by
form of engine bearing tightened by a cottar and simple faith in the treatment. In some cases there
wedge. In the year 1873 I purchased a Coventry has been an entire absence of faith in the means
Machinist's bicycle, with a 50in. driving and 27in. employed. Cases of infantile paralysis and deformity,
trailing wheel weight, 601b. The front bearings where the child has been too young to have any
were about 1in. wide. I rode that machine faith in the treatment; cases where the patients
thousands of miles, and when I sold it in 1889, the have merely come there to try the treatment just to
wheels were as rigid as when new. When the bear-oblige friends. These can scarcely be said to have
ings wore down, the application of a file to the been cured by faith in the means employed. I have
cheeks put matters straight, and they would hold this day seen and conversed with the young girl
enough oil for two days' journey. I could ride that whose foot was condemned to amputation, but
machine at twelve miles an hour on ordinary roads, who is now able to walk well. I have no doubt but
and have done eight miles in thirty minutes on a that her case was one of diseased bone. She did not
flat road. I do not think modern machines are believe in the course of magnetic treatment at first,
faster than this. Some of your readers may know but attended the establishment in obedience to her
the Watling Street? I rode from Rugby to parents. To her surprise, she got better in a few
Dunstable in five hours without a check, and there days, and continued to progress until quite well.
are some big hills on the way. What is required in The cases I quoted in my last letter (32322, p.
a cycle is a bearing of the simplest description, with 249) were selected because they came under my own
plenty of surface to hold a lot of oil, which, in my observation, or, the reports concerning them were
opinion, reduces the friction much more effectually supported by the testimonies of persons to whom
than the so-called anti-friction bearings. You the cases were well known. I could have collected
never see an engine fitted with ball bearings-and many more had I chosen to have asked Mr.
why? Because of the weight of the moving parts. Cole for references. Columns of this paper could
The weight and bearing surface must be propor- be filled with them if numbers were required to
tioned.
swell and add weight to the evidence.
Although Mr. Gerard Smith did not experience
any effects, good or bad, from placing his head
"between the poles of a huge electro-magnet for
twenty minutes," this isolated experiment does not
prove that "the magnetic field has no effect
whatever on the normal human body, or upon
living protoplasm." Mr. Smith has appealed to
numbers, and should, in justice, allow the same
rule to be applied in his test case. I do not admit
the test as evidence in this discussion at all, since
it was performed on the healthy human body. No
one can know better than Mr. Smith that the
sensitiveness of the body in health and in disease
differs considerably. Because a healthy boy
swallows the contents of a whole tube of aconite
globules without experiencing any effect, good or
bad, it would scarcely be fair, in the face of
homoeopathic experience, to say that small doses of
aconite have no effect in a diseased body. Persons
suffering from disease will not stay to ask whether
this or that drug or means of cure has any effect
on the healthy human body. It is enough for me
that they will give relief in pain or cure disease.

Sm.

THE COST OF ELECTRIC LIGHTING. [32370.]-HAVING clearly stated on p. 249 what I wanted, I do not understand why Mr. A. P. Smith should tell us a second time what everyone conversant with the subject knows. I asked plainly enough if any one who formerly used gas, and now uses the electric light, would tell us how the bills compare? I know all about the units, &c., but what I want is the actual figures of the bills, or a comparison from actual experience? And so that there should be no mistake, I will limit the question to London north of the Thames. Surely by this time somebody can give actual experience. Please see first sentence of my letter on p. 249.

ELECTRICAL.

Incans.

[32371.]-1, LIKE "Hysteresis," cannot distinguish the causes of an increase or decrease in the strength of an electric current. In Mr. Bottone's Collegio del Carmine experiment, I can understand that the gradual immersion of the copper plate into the exciting fluid decreases the resistance in an inverse ratio; but I cannot see that the increase in current when the size of the zinc plate immersed is increased is also due to diminished resistance. It appears to me that in order to determine the strength of current produced by a cell there are, besides resistance, two other things to take into consideration. First, the E.M.F., which is a constant determined for any pair of elements in a certain fluid; and, second, the amount of this force exerted which I should suppose is proportional to the amount of zinc submitted to chemical action. The increase in current when the size of the zinc plate is increased, would, therefore, according to my view, be due to the latter. Surely a large zinc plate produces more chemical action than a small one, and as electricity is supposed to be produced by chemical action, an increase in the amount of this action would account for the increase in the strength of the current. If an increase in the size of either of the plates of a cell decreases the resistance in an inverse ratio, when they are both doubled the resistance would be x = 4, but when two cells are connected in parallel, which amounts to doubling both the plates, the resistance is only halved. How is this discrepancy accounted for? F. E. Goodchild.

IS MANGANESE NECESSARY IN LECLANCHE CELLS? [32372.]-A CORRESPONDENT asks this questions. The reply is, Yes, certainly, as without manganese the cell is not a Leclanché. However, a reference to the Electrician of, I think, last week, will discover a paper on the subject, wherein it is shown that part of the oxygen absorbed is derived from the air and part from the manganese, proving that the latter is not without some use. Sm.

THERAPEUTIC MAGNETISM.

Mr. F. Askew presupposes that it is necessary to
excite the nerves in order to do any bodily good.
This is not always necessary or advisable, if excita-
tion of the nerves be taken to mean a thrilling or
similar sensation felt in them. Feelings are often
illusory, and cannot always be trusted. But both
myself and others have experienced a sense of
warmth in the feet and other parts exposed to the
influence of a strong magnetic battery. One old
gentleman always gets his feet warm whilst sitting
near a magnetic machine, although they are rarely
or ever comfortably warm at other times.

can scarcely bring myself into the position of a
critic on anything our good friend "Sigma" writes.
I have so long sat at his feet as a scholar in the
columns of the "E.M." as to feel a reverential
diffidence in touching any of his words by way of
finding fault with them. My long acquaintance
with his mind led me to anticipate his reception of
my letter; but I cannot pass it by without comment.
All that our friend says about magnetism has been
said many times respecting the homoeopathic action
of drugs. Because the drugs are attenuated they
can have no action on the human body. The con-
trary has been proved again and again, and I have
proved in myself that drugs in an attenuated form
can and do relieve pain, and cure maladies.
"Sigma" says, "a magnet can emit no energy.'
If this is the case, may I ask him, What, then, are
the lines of magnetic force? Are those lines
evidences of energy? If not, since they are power
ful to act in attracting or repelling iron and steel,
what relation do their power and force bear to
energy? If I place a steel pen in the palm of my
hand and a magnet beneath it, the pen is attracted
by a force passing through the tissues of the hand.
Is not that force magnetic energy? It performs a
movement, and this seems to demand energy. By
placing the steel pen on my hand I have evidence
of magnetic force passing through the hand. The
pen is only a means of detecting the existence of
this force. It was there before the pen was placed
on the hand; it did not draw its magnetic energy
from me, and its effects on the hand or pen were
neither "moral" nor "mental."

G. E. Bonney.

32373.]-MR. GERARD SMITH says, in letter 32350, p. 274, that "the mere reports of patients are not trustworthy alone." Whilst agreeing with him in the main, I should like to ask him what LOCUSTS. pporting evidences of cure he would deem necesry before accepting patients' reports? I have seen [32374.]-THE "destroying legions"-the "defresh cases at Mr. Cole's establishment before they vouring hosts"-are epithets heard of and read

of in European lands happily free from the greatest scourge which can befall the fields and gardens of the human race! So sudden and unexpected is their invasion, and so swift is their flight, that the long, dark cloud on the horizon soon grows into the rushing horde, consuming every green leaf, and, before sunset, leaving miles of cultivated lands black and bare, as if they had been swept by a conflagration.

Imagine all the bee swarms of England, each insect 3in. long, with spinous legs and sharp mandibles precipitating themselves simultaneously on some promising orchard, and rendering it leafless in a few minutes. No pen can possibly describe their innumerable body, or the havoc inflicted. I have witnessed this winged phenomenon too often in Asia and Africa, creating the most melancholy feelings in my mind regarding the cruelty of nature. Then follows the reproductive force; the myriads of ova next season spring into life, creeping and orawling, consuming the germs of vegetation, until their hideous masses attain the winged state. I have had the wheels of a twohorse carriage so clogged on the plains of South Africa that my progress was delayed. Last year, in India, the railway trains were obstructed, and by the inclosed cutting, of recent date, the same extraordinary occurrence has taken place. Nearly every quadruped eagerly devours the locust, so do the numerous birds; and should a strong, cold wind suddenly arise, the insects are blown into lakes and rivers, furnishing many a welcome meal to the fishes. Mohammedans delight in curries of this insect, both fresh and salted. The dish smelt savoury enough, but I could never overcome my repugnance to this giant grasshopper in tasting it. Only a small percentage is actually killed by all the above consumers; the elements alone are wholesale destroyers. The red specimens are believed by Asiatics to predict war, the yellow as harbingers of pestilence. Eos.

THE DISSIPATION OF ENERGY. [32377.]-OUR Editor having hinted that the discussion of this matter had gone far enough, it was not my intention to say any more. But "F. W. H.," in letter 32344, p. 273, having put one or two pointed questions to me, courtesy compels me to crave space for another word or two. When I stated that force and energy were in perpetual conflict, I did not mean to postulate 36 repulsive force," and then set up a war between attraction and repulsion. This would have been little more than verbal jugglery. My meaning was that while energy always acted, when uncontrolled or insufficiently opposed by force, in the expansion, extension, or dispersion of matter; force, on the other hand, when not prevented by some kind of energy, would integrate matter to the uttermost. Between such influences, which seem opposed in every essential aspect, there can be nothing but conflict. They are the Ormuz and Ahriman of the material world. This is so very patent that it is odd that " F. W. H." should find any difficulty in following it. But from his remark about the coal and the character of the sunshine, it is certain that he has not yet quite thought this subject out, or studied the views of modern physicists very extensively. No one would dream nowadays of calling the solar influence that formed the coal a force. It was waves of radiant energy that dragged the atoms of carbon away from the embrace of the oxygen atoms, in opposition to the force of chemical affinity. When the coal is placed under suitforce able conditions, the again. obtains

1. Lead pipe showing "soil" marks. 2. Butt-joint for tanks. 3. Joint for ship-plating. 4. Lap-joint. 5. Sunk lap. 6. Raised lap. 7 and 8. Laps with nuts, bolts, rivets, and screws. 9. Pegs. 10. Pegs in use. 11. Tapered lap. 12, 13, 14, 15. Ways of notching for hard soldering, 16, 17, 18, 19. Lines showing solder in the joints when finished. 20. The cramp-joint before closing up. 21. Butt-joint. 22. Butt soldered inside. 23. Mitre joint. 24. Outside lap. 25. Inside lap. 26. Paned-down seam. 27. Double seam, 28. Box groove. 29, 30. Pipe elbows. 31. Patent strip overlap. 32. Expansion joint. 33. Raised groove. 34. Sunken groove. 35. Roll joint. 36. Hollow crease joint. 37. Bottom slipped on. 38. Rolled on. 39. Paned-down bottom. 40. Kuocked up. 41. Bottom let in. 42. Knocked over bottom. 44. Part of section of steamer bottom. 45. Ditto of slop-pail. 46. Wrought-iron flange on water-pipe showing hook-joint 43.