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ong time yet the patience of the calculator will source of perturbation. without regard to the nu-going over the paper, as it lies before us, the have to supply the imperfections of analysis." merical labour, and for the masterly manner in arguments in favour of its discovery seem very The method employed by Baron Damoiseau is which the whole of the vast work is conducted," small, and Dr. Olbers must have been guided very nearly identical with that suggested by is undoubtedly that of Professor Rosenberger. rather by what he hoped than what he thought. Lagrange. It will be remembered, when hinting "So complete," remarks the present Astronomer Aided by a powerful instrument, and the transat the method pursued by Clairaut in this diffi- Royal, "are the whole of these computations, that parent atmosphere of Italy, Father Dumouchel, cult subject, we pointed out that there was a if names were taken not from the discoveries of of the Collegio Romano, detected the expected difference between computing the perturbations these bodies, or from those who conjecture their comet on the morning of the 6th of August, close of a comet and those of a planet, though the identity, but from those who from accurate cal- to the computed place, the error amounting to effect is produced by the same cause in both cases.culation on an uniform system, combine the whole about seven minutes of arc in Right Ascension, In planetary perturbations it is possible to inte- of our information relating to them, we should and seventeen minutes of declination. (To such grate the differential variations of each of the call this body not Halley's, but Rosenberger's." of our readers who have no idea of space measured elements of the orbit, but, in the case of a comet, He first, and with the greatest care, computed the on the sky, we may say that that distance is the eccentricity is so large, and the inclination to elements of the orbit from all the observations rather more than a semi-diameter of the moon.) the ecliptic varies to infinity, that it is not pos- that were made at the apparition in 1682. Simi- Rapidly the attention of other observers was consible to develop the disturbing function in a larly, the observations of 1759 were discussed, centrated on the welcome visitor, and observations series arranged according to the ascending and from the method adopted, very great accuracy were showered in from all parts of Europe, Sir powers of these quantities, and we must forego was obtained for the discussion of the next period, James South and Captain Smyth representing the advantage of having, as a means of deter- from 1759 to 1835. The perturbations of all the English activity on this subject. The reduction mining the inequalities of comets, formule, planets (Neptune, at that date, remained to be of the observations shows the 16th November to which, as in the case of planets, embrace an in- discovered) were computed with great precision, have been the day when the distance of the comet definite number of revolutions, and need only with the exception of about 60° of eccentric from the Sun was the least, so that the predic numerical substitutions to give the sought-for anomaly, when the position of Jupiter was such tions of Rosenbergen were but 5 days in error, a results. In order to integrate the differential as to produce great disturbance, and which could degree of approximation that can be appreciated formule of the elements of the disturbed orbit, not be calculated with the same admirable degree only by those who have been engaged in compurecourse must be had to a method of approxima- of precision without a more accurate knowledge tations of that long and delicate nature. The tion, known to astronomers as the method of ofthe comet's orbit. For these 60° of eccentric ano- Royal Astronomical Society of England rewarded mechanical quadratures. This method consists maly, Rosenberger assumed Damoiseau's results, the talented mathematician with their gold medal of dividing the curve described by the comet into and the general effect of perturbation is very ac as an acknowledgment of his eminent services. small portions, in which the alterations produced curately determined. Nor did Rosenberger forby the disturbing forces on each element of the get the effect of such a medium as Professor orbit can be computed. Suitable formulæ pro- Encke had demonstrated to exist. He computed vide the calculator with the means of computing that the effect of such medium would be to acfrom these disturbed segments the total variation celerate the return of the comet by about a week. of the elements in the interval comprised between The Earth hastened the perihelion passage 153 the two extremities of the arc of the trajectory days, Venus about 5 days, and Mercury that is being considered. By these means the and Mars together nearly one day. Includastronomer knows the alteration of the elliptic ing all the perturbations, Rosenberger conelements of the orbit between two consecutive cluded the nearest approach to the Sun would passages of perihilion. Of course, since the only take place on November, 3d. 19h., Paris object is to divide the path of the comet into time. Neglecting the amount of acceleration, small segments, this can be effected either by due to the existence of the ethereal medium, the equal portions of time or equal portions of arc of time of perihelion was expected at November, eccentric anomaly. In either case, the amount of 11d. Oh. Paris time. interval is left to the discretion of the calculator. The method of mechanical quadratures must be adopted while the comet is pursuing that portion of its path near the Sun, but for the parts distant from the Sun an approximate solution is obtained by supposing the mass of the Sun and planets collected at their centre of gravity, and Lagrange gave expressions by the quadration of which the process is made accurate. He demonstrated also that without considerable error, expressions may be found for these last-mentioned terms which will be integrable.*

Damoiseau has applied the method of quadratures throughout for equal intervals of eccentric anomaly, and computed the effect of Jupiter, Saturn, and Uranus only, from 1682 to 1835. Subsequently he calculated the disturbing effect of the Earth. In the first half of the first revolution he appears to have employed the elements deduced from the observations of 1682, and in the latter

The comet continued visible till the 22nd of November, when its near approach to the Sun rendered observation impossible. On the 30th of December, on passing from the Sun, Kreil, of Milan, succeeded in obtaining a view of it, but the southern declination soon rendered it impossible for European observers to continue their observations. At the Cape of Good Hope, Sir John Herschel and Sir Thomas Maclear prosecuted their investigation of its path among the stars, till the middle of May, when it was finally lost sight of, till it shall appear again in 1911, when this generation shall have passed away, and its children be anticipating the infirmities of age. (To be concluded next week.)

SCIENCE FOR THE YOUNG.

(Continued from page 54.)

THE definition being thus briefly explained, it

remains to see how it contains the II. and

But one more effort to determine the elements of the appearance in 1835, remains to be mentioned, that of Dr. Lehmann, which, though in some respects inferior to that of Rosenberger, yet demands very great praise. The distinguishing BY THE REV. E. KERNAN, CLONGOWES College. characteristic of the investigation lies in the fact that the computer has carried back the effect of perturbation to the apparition in 1607, adopting the method of quadratures by equal intervals of time. This additional labour was undertaken to detect, if possible, the effect of a resisting medium. The predicted time of reappearance was by this calculation later than in any other-viz., Nov. 26. The cause of the discrepancy is most likely to be found in the fact that the elements were not changed sufficiently often in computing the perturbations between 1759 and 1835; the frequency of the change, as we pointed out, is entirely at the option of the computer.

III. part of the treatise on mechanics.
I. Force may be prevented from having its
Thus in Fig. 1, the
effects by another force.
force which would cause the weight A to fall,
may be counteracted by an equal weight B at the
opposite end of the cord. There is then pro-
duced what is called equilibrium.

II. Force may be allowed to have its effect Let the entirely, or, more or less modified.

FIG./

FIG. 2

The excitement that was experienced in 1759, at the approaching return of this comet, was as weight B be removed, A falls to the ground with nothing compared to the anxiety that was felt in 1835, to effect early observations of it. In January, 1835, Dr. Olbers published a paper in which he expressed his opinion that the comet would be visible in the spring of that year. conclusions are based upon facts drawn from the

His

half the elements deduced from the observations
of 1759. In the second revolution the elements
are altered for every 30° of eccentric anomaly.
These alterations do not appear to be sufficiently
frequent. As the result of Damoiseau's calcula-
tions, he predicted the return of the comet to
perihelion on the 4th of November, 1835, at 8h.
P.M., Paris mean time.
Some years later a second attempt to deter-experience of previous returns, assuming that the
mine the perihelion passage was made by Ponte-
coulant. In narrating the history of the calcula-
tions of this comet in a chronological order, we
should have mentioned that Burckhardt com
puted with admirable precision the elements of
the orbit from Flamsteed's observations in 1682,
and Messier's in 1759. From these elements
Pontecoulant endeavoured to determine the path
of the ellipse that would be described in 1835.
It would be to lengthen out this paper to a
tedious length, to pursue the course of Ponte- self luminous, is proportioned to
coulant in his elaborate calculation. His method

comet has sustained no sensible diminution of its
mass. The last observation of the comet in 1759
was effected by Messier, when its distance from
the Sun was about 1-68, and from the earth 1:42
(the Earth's distance from the Sun being regarded
as unity). Olbers remarked that about the be-
ginning of March, the comet's distance from the
Sun and the Earth would be nearly the same
378. But as the light of a heavenly body, not

1

R2 D2

(R being

is that of Lagrange, adapting quadratures the Radius Vector, and D being the distance
throughout. The result to which his final calcu-
lations led him was that the comet might be
expected to approach nearest the Sun on No-
vember, 12d. 17h. Paris mean time, or about
a week later than the epoch assigned by

Damoiseau.

But the investigation on which is bestowed the greatest care, and the one "that is most remarkable for the extraordinary completeness of its detail, for the pains taken to include every possible

* Memoir Roy. Ast. Soc., Vol. IV.

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from the Earth) the comet in the beginning of the full force acting upon it. Let B be replaced
March would be about 30 times less bright than by a small weight; A now falls more slowly. In
when it was last seen by Messier, and, conse- both cases there is produced what is universally
quently, the probability of its being seen, small in called motion.
the same proportion. Nevertheless, Dr. Olbers
urges on astronomers the necessity of continual
and careful sweeping to attempt to discover it,
and to aid in its detection, computed two ephe-
merides on the assumption of its perihelion pas-
sage taking place at the 1st and 11th of Novem-
ber. This paper gives some idea of the anxiety
that was felt at its approach, for on carefully

III. Force may be allowed to have its effect for a short time, to be overcome in its turn by In the force which it at first overpowered. Fig. II. is represented a coiled spring with a The weight being raised and weight attached. let gently fall, at first the spring is stretched beyond its position of rest, dotted coil; then the force of the fall being exhausted, the coils of the

Spring recover that position. Again the weight falls, and again the spring recovers. This falling and rising continues until the force of the first fall is worn out, by causes to be seen later. Here is produced vibration.

The laws of I. are called the equilibrium; or in one word, Statics; of II., the laws of motion or Dynamics; of III., the laws of vibration; which might be entitled Palmotics. This third point, in practice, chiefly regards acoustics (sound), as shall be explained.

The three conditions of force, as above, are to be found in the solid, liquid, and gaseous state, giving new divisions; statics of solids or Statics; statics of liquids, Hydrostatics; statics of gases, Pneumatics; dynamics of solids, or Dynamics; dynamics of liquids, Hydrodynamics; dynamics of gases, Pneumatics; palmotics (acoustics) of solids, liquids, gases.

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GENERAL PROPERTIES OF MATTER. It will be a great deal done towards uninterrupted onward progress in the study of mechanical principle to have a good notion of the many properties which bodies possess. They may be divided into two classes, essential and accidental. To those which are more importaut amongst them, will be applied the form laid down in the explanation of the word study-i. e., their laws, proofs and explanation shall be studied.

SECTION I.

ESSENTIAL PROPERTIES OF MATTER. These may be taken singly or in groups, as they are more or less important. Though these latter may not require details of laws, they may have applications important or interesting.

§ I. EXTENSION, FIGURE, IMPENETRABILITY. I. Extension is the occupying of space by length, breadth, and depth. A body cannot be imagined to exist without these.

Application I.-Rules, Measures.-What these are is sufficiently understood from daily experience, and from treatises of arithmetic with which the student is supposed to be familiar. They are, in short, conventional means of representing portions of space. Any abstract discussion of this, or similar subjects, has no place in an elementary series of mechanics.

Application II.-Reduced Space.-By this is understood the proportional representation of a large space by a much smaller; as, for example, when several miles of a country are represented by as many inches on a map. And here it is most important to remark that the greater the difference (the greater the reduction) the more exact must the instrument be; a very small portion of an inch may cause great error. Sub-Application.-Heavenly Space. The great extent of the Heavens, which is represented by very small space in our observing instruments, makes it imperative that the greatest exactitude be obtained when there is question of declaring absolute space, otherwise errors of even millions of miles may be admitted.

gives to many bodies a fixed determined form,
by what is called crystallisation. This subject
has its own place in chemistry.

III. Impenetrability signifies the impossibility
of two bodies occupying the same space at one
This is the strict, but not
and the same time.
When a nail is driven
the ordinary notion.
into a block of wood, it is said to penetrate the
wood. Such is not true; the wood particles are
only pushed aside. The wood does not exist in
the space occupied by the iron. In the Fig. 3
there is no water in the space occupied by the
immersed body A.

FIG. 4

But of the three states the impenetrability of
the gaseous is the most remarkable, and may be
shown most distinctly
to the eye. Fig. 4
rep resents a glass re-
ceiver inverted, and
forced down into a
vessel of water. Not-
withstanding the ten-
uity of the air, the
water cannot pass up
into the receiver, to
any great height.
The air cannot be
pushed aside, it re-
sists; it may be forced
into a smaller com-
pass; it yields slightly,
as a whole, to the ex-
ternal pressure of
the water, and lets
in a quantity varying with the height of the
water, in the outer vessel. A candle floated
upon the water helps to make the inside level
Were it not then for this
more apparent.
making place, the smallest pin could not be
forced into a solid, or into a small recipient
filled with a liquid or a gas.

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§ II-DIVISIBILITY.
Matter can be reduced to smaller and smaller
dimensions. The delicacy of the instrument
seems to be the
only limit.
What is possi-
ble beyond this
point is of no
in
importance
mechanics. The
question is left
then to chemical
and speculative
philosophy. Di-
visibility of
space serves to
introduce a some
what important
instrument.

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10

15

be brief and clear, a few points.

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1. Construction. A measure is made, shorter by one division than a ceratin portion of the given врасе. This portion is determined by taking divisions, as many as there are units in the denominator, of the required fractional parts. The shorter length, divided into as many parts as there are units in the same denominator, constitutes the venier. Example: Let it be required to show 10ths of a division of the rule A B, Fig. 5. The vernier is made 9 divisions long, and divided into 10 parts. In the same way, if

1

1

20

Application III-Pyramids.-Recent researches
of Piazzi Smyth, have confirmed the opinion of
Mr. John Taylor, of London, that the Great
Pyramid of Egypt was constructed with the
design of fixing a system of measures for the
human race. The Hebrew measures, and those 30
of many countries, are found to have been divisions long, and divided into 20 30 parts. In
established upon this system.

be required, the vernier will be 19-29

1

II. Figure signifies shape, form. Besides the the most general form representing any fraccountless figures which art can produce, Nature

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than those of the rule A B. Consequently, if when laid upon the rule, any division of the vernier correspond to a division of the rule, the divisions of the rule towards its zero will show 1, 2, 3 n fractional parts of its own divisions; or, in short, the figure of the vernier, which corresponds, tells the fractional parts. Should no line correspond, the nearest correspondence is taken, and the fractions estimated as before, either within or beyond the limit. The error, in plus or minus, must be less than the fraction for which the vernier is constructed; therefore, by more and more exact vernier, the possibility of error can be reduced as circumstances may require. In many ordinary measurings one millimetre more or less would be of no consequence; in many phy

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10 too much or too little. Circumstances determine which to take. Other methods of applying the vernier may be met with, but these return in principle to the one explained.

IV. Sorts.-Verniers are of two sorts, straight and curved. These latter are used for the fractional parts of the divisions on a circle. Fig. VII., A B are of circle V vernier. This form is sometimes called the Nonius, from the name of the inventor, a native of Portugal.

V. Limit.-Delicacy of division is the only bar to indefinite vernier division. Practically,

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Sub-application.-Cathetometer. The object of this instrument, invented by Dulong and Petit, and perfected by Gambey and Pouillet, who named it, is to measure, by means of a vernier, the difference of level, of two points in the same, or different vertical. In its essentials, the Cathetometer, is a vertical rule of brass, divided into millimeteres. Along the rule slides a telescope, in the inside of which, in a fixed place, are the very fine threads crossing at right angles a Fig. 8. The slide which carries the telescope is provided with a delicate vernier, by which

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scope, has a spirit level L, and is brought to exact level by the screw D. The slide E has an opening at O, through which the divisions of the rule are seen; and along which is the vernier V; M its microscope, to be moved as required. To the slide E a second slide F is connected by a screw H. This slide F can be tightened to the rule by the screw K. For use, the slides E and F are drawn up by hand until the crossing point of the telescope threads seems to be more or less on a line with the first surface. By the screw K the slide F is fixed, and by the screw H the slide E is gently raised until the crossing point

Only a small part of the pillar is seen.

The cap and greater part of the steel pillar are concealed by the rule, which must show full front.

is in exact coincidence with the surface. The
position of the vernier zero is noted accurately.
The second surface is examined with the same
precaution; and the difference of the vernier
zero in the two positions represents the difference
of level desired.

Jamin, in his Cours de Physique de l'Ecole
Polytechnique, considers the cathetometer so
very useful an instrument that he goes at some
length into the conditions requisite for good
action. These would be here out of place, as in-
troducing unknown subjects. The same may be
said once for all, as regards omissions of details of
instruments and machines hereafter; as much as
possible, all points not yet explained to the
student, will be kept out of view until their own
principles have been studied. Though this
method may not be agreeable to a general reader,
it is of immense advantage to one who is only
entering upon scientific study. For thus each
point receives his undivided attention, its prin-
ciples are more quickly studied and understood;
that weariness caused by frequent divergence
into, and forced return from various trains of
thought, is avoided; and, above all, the danger of
mere superficial knowledge is almost completely
guarded against. It then is a source of pleasure
when the course has been completed, to review
instruments, machines and combinations of
machines, as a whole. Each part shows itself
with its principles clearly present to the mind;
and not as another element, to increase the
general confusion of ideas, so commonly conse-
quent on mere general reading.

(To be continued.)

ON THE DRESSING OF LEAD ORES.
PAPER was read on this subject before the

The washing operations commenced by turning a stream of water into the "teams" containing the "bouse," which was raked out by a man on to a grate, and there hand-picked. The author used two grates, the higher one with spaces of 1 inch, and the lower one of inch, in preference to one grate with spaces inch wide, as usually employed. The stuff passed through the second grate into a stirring trunk, where a partial separation of the coarser particles from sludge and slime was effected. The coarser particles were of a size convenient for hotching, and the common hotching tub could treat from 8 to 15 tons of stuff per day. Between the waste, which was wheeled away, and the pure ore, there was an intermediate layer of what was called "chatts," consisting of particles mixed with ore which could not be separated without further sub-division. This was effected by means of a crushing mill. In England from 25 tons to 30 tons was a fair day's work to pass over one grate. The author found, by the use of two grates, that 40 tons could be passed, without any increase of labour, at a cost of about 2s. 6d. per ton of clean ore produced.

The ore which passed through the coarse wire bottom of the hotching sieve accumulated at the bottom of the tub, and was called "smiddum." This was rendered fit for market by further preparation in the plain buddle. The sludge deposited in the trunks attached to each grate was prepared in a round buddle. A separation having first been made of hard lumps, small stones, or chips of wood, &c., the sludge was delivered at the centre of the buddle accompanied with water. The bottom being inclined outwards about 1 in 10, the particles were carried by the water in that direction ; the heaviest and richest being deposited nearest the centre. The buddle described was larger in diameter, and treated nearly four times mcre stuff then that usually employed. The

A Institution of Civil Engineers on the 5th water on leaving the sludge trunk carried with

inst. by Mr. T. SOPWITH, Jun., M. Inst. C.E.

This communication was limited to a description of some works the author had had occasion recently to establish in Spain for the dressing of lead ores, as a general account of the present state of such operations in England could not be satisfactorily given in a single paper. Moreover, as regarded this branch of mechanical engineering, Germany was in advance of England. By dressing was to be understood the art of obtaining from the raw material extracted from the mine, called bouse or mine stuff, the pure ore it contained, to the rejection of the impurities with which it was associated. Bouse might be said to yield, in an ordinary way, from 5 per cent. to 25 per cent. of galena, which when pure had a specific gravity of 7.75, and produced 86 per cent. of metallic lead. The lead ores of commerce were usually dressed to a tenour of from 74 per cent. to 78 per cent., though argentiferous ores were frequently delivered with a lower percentage. All galena was mixed with silver; but the term argentiferous was only applied to that in which there was upwards of 12oz. of silver per ton. In dressing, the principle applied was that of separating the lead ores by means of their readier gravitation. This operation was easy or difficult according as the accompanying impurities were of greater or less specific gravity.

At the works referred to, about 350 tons of lead ore were prepared per month. There were two dressing floors, the higher and the lower. On the former manual labour was principally em. ployed. On the lower floor the stuff was treated which required to be passed through the crushing mill; and it was more particularly this machinery and method that it was the purpose of this paper to describe. On the higher floors from 200 tons to 220 tons per month were prepared, or two thirds of the entire quantity. Two systems of one, by "tribute" or "bingtale," where the men paying the miners were adopted in mineral mines; were paid in proportion to the amount of clean ore the mine stuff excavated by them produced; the other," tutwork" or "fathomtale," where they were paid by measurement. The adoption of the former system introduced complication, and more expense in the dressing operations than the

latter.

The author, in describing the various machines, and the quantities of work they could deal with fixed as a standard the richness of mine stuff treated at about 12 per cent. (by weight), equal to work which would be known in the North of England as producing 2 bings per shift.*

A bing was eight ewts. A shift was eight waggous,

carrying about one ton each.

it a certain amount of slime, which was deposited in pits, and was subsequently treated in a machine called a Brunton's Cloth, the action of which was described, as also of the dolly tub, by which the slimes, after being concentrated in the Brunton's machine to about 45 per cent., were further enriched to about 70 per cent., and so delivered for sale. The crushing mill in common use in England was described, and the inconvenience attached to it, as compared with the simpler form used in Germany, was pointed out. In the apparatus that had been referred to, it was probable that about 80 per cent. of the lead ore produced in England was prepared.

On the lower, or crushing mill floors, which the author had erected, some attempts had been made to secure continuity of action by the use of self-acting machinery, wherever it was possible; though from the circumstances of Spanish labourers being employed, who were totally unaccustomed to the use of machinery, it was necessa y that the machines should be of the simplest kind. The stuff which required crushing was conveyed in waggons to the lower floors, being first broken to a size which would pass through a 5-inch ring. This was effected by manual labour, in preference to a stone-breaking machine, as the former allowed of a separation ef a small quantity of pure ore, and of a large quantity of waste, which would afford unnecessary work for the crushing mill. The stuff, after being emptied from the waggons into the hopper of the crushing mill, was passed through the rollers, and, when crushed, was elevated by a Jacob's Ladder, and delivered into a classifying trommel, composed of two shells, an outer one of perforated iron plate with holes 1 millimetre in diameter, and an inner one with holes 10 millimetres in diameter. The crushed material was delivered into the inside of the trommel at one end, and passed onwards, the were got rid of through the outer shell, the inner trommel being inclined. All the sludge and slime shell retaining and delivering apart any particles over 10 millimetres in diameter. These were returned to the crushing mill, to be again passed through the rollers, and the particles, ranging in size between 1 millimetre and 10 millimetres, were delivered at the further end of the trommel, and passed on to a second, or sizing, trommel, composed of one shell only, and were then subdivided into four sizes, viz., 24, 5, 73, and 10 millimetres, each size being treated in a separate hotching tub. For the operation of hotching, the convenience of having all the particles treated of one, or nearly of one, size, was obvious; and Th: hotching machines employed were entirely in some cases of refractory ores it was a necessity.

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THEM WITH THE MICROSCO PE.

BY J. MUTER, PH. D.
(From the Food Journal.)

self-acting and continuous in action; a fast and | The cost of preparing similar work in England, | COFFEE ADULTERATIONS, AND HOW TO DETECT a loose pulley being attached to each machine. with machine crusher and machine hotchers, was, Contrary to the form adopted in England, the the author believed, about 2s. 6d. per ton of clean sieve was stationary, the water being put in mo- ore. The whole of this machinery was driven by tion by means of a loosely-fitting piston. The a 10 h.p. portable engine, supplied by Messrs. HAVING seen in our last number the properties of coffee, stuff was delivered into a small hopper, and Ransomes, Sims, and Head. The cost of erection let us now take a glance at those of its chief adulterant. travelled the length of the sieve, a distance of 28 of the crushing mill floors complete, including Chicory, as employed for this purpose, is the dried and inches, by which time a perfect separation was the engine, was about £1500. The same arrange-roasted root of the common endive, so dear to the lovers of cffected. It had been found advantageous to in- ment in England would have cost about £1200. winter salads, as a substitute for lettuce. This plant is to crease the length of the stroke, and the number Most of the machinery was supplied by Messrs. be seen growing wild in many of our hedgerows, and belongs of strokes per minute, for the larger sizes. By an Sievers and Co., of Kalk, near Cologne. No to the botanical order of Composite. It is very similar to the ingenious movement, a quick down stroke and a separate crushing mill for the preparation of common dandelion, which belongs to the same order, but it is slow return stroke had been given to the piston. "chatts" had been erected, as when the "chatts readily distinguished by the colour of its flower, which is The crushing mill was more compact than the had been allowed to accumulate, the present blue, while that of the dandelion is yellow. The chicory form used in England, the rollers being kept in machinery could be adapted for their treatment root also bears a great resemblance to that of the latter contact by the compression of india rubber buf-in an hour or two, advantage being taken of a plant, being, like it, soft, and exuding when squeezed the fers, in place of a long lever, with a heavy weight time when new rollers had been put in. milky juice so well known to all of us who have enjoyed, as attached. The sludge, which passed through the children, the pleasure of wandering in the fields. holes of 1 millimetre in diameter, in the first, or classifying trommel, was delivered into a separa tor,-an iron cylinder about 24 feet high,-where it met a stream of water of sufficient strength to carry the smallest and lightest particles upwards. and deliver them into a launder, whence they were conveyed, by the water, to the sludge trunks and slime pits, and were subsequently treated in round buddles and in Brunton's Cloth. The coarser particles were prepared by manual labour, in a common trunk or tie.

The amount of work crushed and prepared on the lower floors was about 55 tons per day of ten hours. The actual cost in Spain was 21s. 2d., but the equivalent of labour would be performed in English mining districts for 13s., the latter eum being at the rate of 2 83 pence per ton of raw material treated, or 2s. per ton of clean ore produced. If, however, self feeding apparatus was introduced to supply the hotching machines, which could easily be done, the latter cost might be reduced to 2:07 pence, and 1s. 54d. respectively.

Oar wild English plant is not, however, so much esteemed

The author observed that whereas, in England, the machinery employed in dressing operations in the market as the German and French varieties, which are was for the most part made at the mine with the specially cultivated for mixing with coffee. The following ordinary staff, in Germany there were manufac-analysis will show the composition of chicory root in its tories giving employment to four hundred hands, dried state, and also that of its ash, to which we shall have dedicated almost exclusively to the construction occasion to refer hereafter:of dressing machinery; and it was not surprising to find, in the machines issued from them, better and durability than those used in the mines of proportions, greater elegance, and more efficiency this country.

been in use for two years, and, having given good
The machinery described in this paper had
results in Spain, no difficulty need be feared in
its application elsewhere.

EXPERIMENTAL PHYSICS.-A contemporary states that the Imperial Academy of Science, Lille, has offered two prizes-one for the best work on some of the thermometer in medicine. The prizes will conbranch of experimental physics; the other on the use sist of 1000 francs each.

I-Dried Chicory.

Moisture..
Gum
Sugar..
Extractive (bitter)..
Fat.

..17.480

20-416

11.166

.18.000

1.066

Woody fibre, &c..
Mineral matter..

.29.202

2.670

-100-000

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From these results it is evident that this plant contains no principles which would render it to any extent a useful sub

stitute for coffee, as we look in vain for the caffeic acid, or the theine, already shown to exist in the latter article. But what shall we say if, besides containing nothing valuable, it should be proved to be positively injurious when freely consumed? Let us hear Dr. Johnston on this subject:-"Taken in moderate quantities, the ingredients of chicory are probably not injurious to health, but, by prolonged and frequent use, they produce heartburn, cramp in the stomach, loss of appetite, acidity In the mouth, constipation with intermittent diarrhoea, weakness of the limbs, tremblings, sleeplessness, a drunken cloudiness of the senses, &c. At the best, therefore, chicory is a substitute for coffee to which only those to whom the price is an object ought to have recourse." Το these remarks we would add that we prefer not being poisoned even at the most moderate cost; and in cases where "price is an object," we would advise the public to abstain from paying anything at all for such a filthy beverage as chicory-coffee undoubtedly is to persons of unvitiated taste. We might bring up many other charges against this nasty infusion, but we will only give one more, and that is a dictum of Dr. Boer's, to the effect that the continual use of chicory causes amaurosis, and, consequently, blindness. Since giving our coffee results last month, we have been seriously remonstrated with by a grocer, who declares that he and his brother tradesmen put nothing else into their coffee but chicory. This is, however, only a repetition of the old story, told long ago by Dr. Pereira, who said that "while the grocers, on the one hand, cheat their customers by adulterating coffee with chicory, the chicory dealers in turn cheat the grocers by adulterating chicory." Whether the grocers are, or are not, the chief sophisticators, is comparatively immaterial, for the fact remains that the public continue to suffer. The grocers cannot, however, be held innocent, as they buy ground chicory, which article they can purchase at a cheaper rate than they could the dried root itself; and of what then do they, in their innocence, imagine it to be composed? Out of twenty samples of ground chicory purchased lately in London (but of the analyses of which we have not space at present to give details) more than half were found to be adulterated.

2. SOURCE OF LIGHT.-The best light is that reflected
from a white cloud on a bright day, direct sunlight being
always avoided; but, if the day be dull, good lamplight is
much to be preferred to bad daylight. The best source of
artificial light ss that of a good moderator or paraffin lamp,
which should be so arranged in height as to bring the flame
about halfway between the stage and the mirror, and about
a foot away from the instrument.
chimney of the lamp should be fitted with a reading-shade,
The upper part of the
to throw the light down on the mirror, but prevent its
being diffused about the room, exactly like the lights over
a billiard table.

3. MOUNTING THE OBJECT.-For this purpose the operator
should be provided with some slips of good patent plate glass,
3in. long by lin. wide; also with a box of thin glass covers,
cut either in squares or circles, though the former are the
cheaper, and do quite as well. He should likewise get some
stout needles and fit them into small pieces of wood to act
as handles, leaving only about 4in. of the point end of the
needle sticking out. When about to examine the object, he
should place a slip of glass on a piece of white paper, and put
a few grains of the coffee (taken from the sample on the point
of a penknife) near one end of the slip. This portion of coffee
is now to be moistened with a drop of water, and allowed to
soak for some time. The operator then takes a pair of needles,
pieces, so thin as to be almost transparent.
and by means of them thoroughly tears all the grains to
A few of these
fragments are then to be drawn to the centre of the slide,
moistened with a drop of water, and a thin glass cover to be
adroitly dropped over them, taking care, by letting one end
of the cover down first, to expel all air bubbles. The object
the complete avoidance of air bells is very difficult, and it is
is now ready for use; but, until one has had some experience,
therefore advisable for the operator to make himself familiar
with their appearance under the various powers of the micro-
scope. The same hint applies to pieces of hair, which are
apt to fly about, and through which, along with air bubbles,
most ludicrous mistakes have been made by inexperienced
persons.

4. EXAMINATION OF THE OBJECT.-The slip, with the
object mounted, is to be placed on the stage of the micro-
scope (which has been previously fitted with the 4-in. power
and "C" eye piece), and the body of the instrument is to be
brought down to within little more than half au inch from the
object. The operator now looks into the instrument, and
The focussing is then to be completed by the fine adjustment,
gently turns the body farther down till the object appears.
and the whole object minutely examined by moving it about
gently in various directions. It is always advisable to
acquire the habit of keeping both eyes open when looking into
the instrument; and this ability to, as it were, concentrate
than would be imagined, and is a great saving to the sight,
all your thoughts on one eye is much more easily learned
which is apt to be impaired by much labour at the micro-
5. MICROSCOPIC APPEARANCES OF PURE COFFEE.-All
our preparations being now complete, we look at a sample of
pure coffee, and find it presents an appearance similar to
that shown in Fig. 1. We notice that there are two totally
distinct forms visible. (1) Several little flat fragment's
marked all over with irregular angular cells. These are
fragments of the body, or substances of the sced; and the
cells are those which contained the essential oil, already
referred to last month. (2.) A number of peculiar oval, or
rather lance-shaped bodies, resting on a fibrous membrane,
and having tooth-like oblique markings between their edges.
These are fragments of the outer skin or testa of the seed,
and are wonderfully characteristic of pure coffee. None of
those structures appear in any of the usual adulterations of
this substance.

We now turn to the detection of the adulterations of coffee. Many simple processes have been from time to time proposed, to ascertain whether this article be pure or not, without say-scope, ing exactly what is the adulterant; and of these we subjoin a few.

1. Take the packet of coffee as it comes from the grocer's, in your hand; and, having given it a good squeeze, lay it gently on the table, and open it. If the contents be found adhering together in a cake, the sample is not pure. 2. Drop gently a teaspoonful of coffee on the surface of a glass of water, and observe if any of it sinks immediately; if so, it is bad. Let the whole be now slightly stirred, and notice the colour imparted to the water. If this be a decided brown tint, then the coffee is adulterated, most probably with chicory or burnt grain of some kind.

only that in this case two good things would be spoiled, whereas chicory is too nasty to spoil at all. The simple fact is that, as a rule, the poor get little or no coffee in their shilling mixture, while the grocers get that sum per lb. for a substance which would not fetch 6d. per lb. if it were sold in ts own name. But we live in a country of "vested interests," and as the grocers have a "rested interest" in this legalised, under a trifling restriction, which was seldom even adulteration, it is temporised with, and was for a time actually complied with.

In conclusion, we have simply to ask that the public should somewhat bestir themselves, and apply the spur to our tardy legislators, so that it shall be made a misdemeanour to sell, under any circumstances, a mixture of chicory and coffee. This would not hurt any of the chicory epicures, as they could still buy their succulent mouthful in a separate form, while it would protect the great mass of the community from a daily-perpetrated fraud." Our authorities every now and then make a spasmodic dash at something, and lately their hobby has been "tea dust" and "re-dried leaves; " but after all, even with the terrible addition of the frolicsome Chinese pigs, about which we have heard so much during the last few weeks, the sale of such commodities is no worse than the daily winked-at traffic in chicory-coffee.

FRICTION.-VII.

BY C. DRAPER, A.B., L.C.E.
(Continued from page 33.)

THE WEDGE. As the characteristic property of the wedge is that it owes its mechanical advantage to the existence of friction, it will be proper, in this series of articles, to give at length an account of it.

As the wedge is sometimes, though rarely, urged between the resisting surfaces by pressure, we have a theory for its action founded upon statical principles, but almost invari ably the wedge is driven by means of impact or a blow; we must therefore look to dynamics for the solution of the problem of the wedge in this case.

the

FIC.13

A

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be an isosceles wedge, P the pressure acting at right angles
To commence with the 'statical theory, let A B C, Fig. 13,
to A B, and let D E and
D'E' be perpendiculars to
the sides of the wedge
points of contact between
erected at D and D the
the sides and the resisting
surfaces, or, rather,
points through which the
resultants of the mutual
pressures pass, for the wedge
may be in contact with the
resisting surfaces at several
points. Since everything
is supposed to be symmetri-
cal on each side of the axis
of the wedge, D and D'
will lie on the same horizontal line, but it is clearly matter o
indifference where the line D D' is situated, since the ques-
tlon is one concerning angles alone.

Now, when the wedge is on the point of moving under the influence of the pressure, P must be in equilibrium with the reactions Q'Q' acting along D E and D' E', and the frictions

3. Make an infusion of the coffee in the usual way, pour Having changed our slide, and substituted pure chicory forμ Q'acting along D C, D' C, at right angles to the re

some into a cup, and let it stand till cold; if a skin or scum should form on the surface, there is reason to suspect baked animal matter, such as horse's liver.

If, however, we seek methods of discovering the precise adulterants employed by means of chemistry, the subject becomes at once much more difficult, and the results not always reliable. One method is to treat 25 grains of the sample with an ounce of ether, in a closed bottle, for an hour, with frequent agitation; and then, having poured off the solution so obtained into a weighed watch glass, to evaporate to dryness; ascertain the weight of the residue. The undermentioned matters, treated in this way, gave the following results:

Coffee (plantation Ceylon)...............375 grains
Chicory (best English)....................150
Roasted Grain..

90

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But it

6. MICROSCOPIC CHARACTERS OF PURE CHICORY.-
pure coffee, we at once see a vast alteration. Here are no
lance-shaped bodies, nor angular cells, but instead we have
the appearances shown in Fig. 3. We now notice a mass of
form the principal portions of the substance of the chicory
round and elongated cells, evidently of a soft tissue, which

root. We also observe a number of long tubes laid in bun-
beautifully marked surface. These tubes come from the
dles over the cells, having a most characteristically and
except for the similar tubes of dandelion, which we will next
centre of the root, and, once seen, can never be mistaken,

describe.

are shown in Fig. 4, and are so similar to chicory as to be
7. MICROSCOPIC CHARACTERS OF DANDELION.-These
readily mistakeable for that root. On examining them more
minutely, however, with a in. power, a difference is
observable. The cells are more elongated, and the tubes are
more decidedly marked in complete rings, while here and
there we find masses of a structure closely resembling the
ribs of an animal,

In Fig. 2 we show the appearance of adulterated coffee, in
which the reader will recognise all of the structures above
mentioned. For the detection of roasted grain, we depend
mainly on the appearance of granules of starch, which can
be identified by their size and shape. The cells of turnip
are much larger than those of chicory, while particles of saw
dust, especially mahogany, can be picked out from coffee by
means of a needle, and readily identified. Mineral colouring
matters may be discovered by burning some coffee in a
small porcelain crucible, when, if the ash be red, it is certain
that venetian red, or other ferruginous earth, has been added
to deepen the colour.

actions Q Q', therefore the resultant of Q and μ Q acting
along D K, making an angle with D E, together with the
resultant of Q' and u Q, acting along D'K', must be in
brium, calling these resultants R and R', we must have the
equilibrium with P; therefore, by the conditions of equili
components of R and R' parallel to P equal to P.
Let i be the semi-angle of cleavage of the wedge, or AC B
= 2i, then since R and R' are manifestly equal, we have
2R sin. (i) = P.

And if we wish to know the pressure T exerted by the wedge
in any other direction, making an angle a with D E, we
must have the component of R in this direction equal to T, or
R cos. (a + 9 = T.

Equating the two values for R found from these two equa-
tions, we have
(a + $)
sin. (i + )

P

T = ---- X
2

COS.

If a = 0, then T becomes equal to Q, and its value given by

[merged small][merged small][ocr errors][merged small][merged small]

If ai, then T becomes borizontal, and its value is given by

P T = 2

X cot. (i+ $).

Let us now suppose that the wedge has been forced into its position, and that it is required to find the force P' necessary to extract it again. In this case we have the reactions aiding P', to that R acts on the other side of E D at the angle; we have, therefore,

Several years ago (in 1852), when public attention was mach directed to this subject, Messrs. Graham and Stenhouse published a report "On the mode of detecting vegetable substances mixed with coffee." They found that the most striking points of difference between chicory and coffee consisted in the much greater quantities of grape sugar and sand which existed in the former than in the latter. A reference to the various analyses in the present article, and that of last month, will easily show these distinctions. unfortunately happens that an equally great proportion of sugar exists in most succulent roots, such as dandelion, beet, and parsnips, and that in wheat and most kinds of grain the silica is as large as in chicory. Taking these points into consideration, we cannot therefore place any great reliance on As in this worid partisans can be found for almost any chemistry for the detection of such adulterations as form the dogma, no matter how ridiculous it may be, provided that it subject of our present consideration. On hearing this, is only asserted loudly and unblushingly enough, so our many of our readers will doubtless exclaim: "Well, if che-grocer friends have, by dint of continual asseveration. got a mistry cannot help you, how did you make the investigations large number of people to positively believe in chicory-coffee, reported last month?" We answer, by means of the micro- and call this filthy root an improvement! The terrible scope; and we will now endeavour to show how this instru- absurdity of this idea must be manifest to any one who ment is used, and how any person possessing one may easily glances for a moment at the subject. Chicory is a root, while coffee is a seed. The credit of first seriously calling attention to the use of deprived of the influence of sunlight or air, only contains a The former, buried in the ground, the microscope as a detector of adulterations belongs deci- few of the crudest vegetable matters, so to speak; while the dedly to Dr. Hassall, whose food examinations created so latter, flourishing under a tropical sun, has all those complimuch sensation about fifteen years ago; and it is now impe-cated and refined organic principles, such as alkaloids, for the ratively necessary that every analyst who turns his atten- formation of which the action of light, &c., appears to be tion to food should be not only a good chemist, but also a absolutely necessary. The advocates of chicory adulteration practised microscopist. In treating this branch of our sub- know well that it produces a sensation of oppression in the ject, we will divide it into distinct heads for more easy stomach, and they take advantage of this to pretend that reference. persons who cannot discriminate between that quality and chicory-coffee has strength, and are believed by ignorant And indigestion, and whose palates have long since been thoroughly vitiated. Another cry of these apologists for adulteration is, that, thanks to chicory, coffee is brought down within the means of the poor, who otherwise could not afford to drink it. This is very like bringing down champagne for the use of the poor by adding three-fourths of small beer,

examine coffee.

1. MODE OF EMPLOYMENT.-The microscope is to be placed upon a steady table, so that the source of light shall be on the left of the observer, and the "body" of the instrument is to be placed in a slightly inclined position. The operator, looking into the instrument, is then to move the mirror about, with its reflecting surface turned to the light, until a perfect illumination of the microscope is produced.

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