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The English Mechanic

AND

Saturnium," in which he showed how the appear- | another sketch, made with the same instrument
ances he had observed were produced by a thin and power, on February 10 of the same year, at
flat ring surrounding Saturn's globe, and situated 11.50 G.M.T. The minute dot of light, appa-
in the plane of his equator. On the night of the
13th October, 1665, Dr. Ball, and his brother,
Mr. William Ball, of Minehead, in Devonshire,

[graphic]

MIRROR OF SCIENCE AND ART. detected that this ring was divided into two by a

FRIDAY, AUGUST 19, 1870.

SATURN.

BY A FELLOW OF THE ROYAL ASTRONOMICAL

SOCIETY.

HERE That can, we think, be very little question System, the most wonderful in aspect, as in physical structure, is the planet whose name heads this article. In fact, we believe that no one ever contemplated Saturn for the first time in a telescope of adequate power without an exclanation of surprise at the extraordinary spectacle presented by a huge globe, suspended in space, belted like Jupiter, and surrounded by an (apparently) dense and solid ring or rings of light. We have purposely deferred any reference to this planet until his arrival at a position in the

that

black line, which has since been known as " Ball's
division." This was re-discovered by Cassini, in
1675. It is worthy of notice that William Ball
must have been a very assiduous observer of
Saturn, as we have it on the authority of Huy-
ghens that he saw the bands or belts upon the
body as early as 1656. Inf 1662, Auzout seems
to have seen the shadow of the planet upon the
ring. Other discoveries we shall advert to in
describing the various appearances presented by
Saturn when viewed with the optical aid now at

the command of astronomers.

rently a detached part of the ring, was in reality a satellite. We may add that the ring disappeared again in the May following of the year in which these drawings were executed.

We have referred to the appearance and diswill perhaps make our subsequent observations a clear conception of the reason why this remarkappearance of the ring (or rings) above; and it Assuming then that the student has acquired rather more intelligible, if, prior to entering into able appendage varies in appearance from a wide revealed by the telescope, we try to give some appears only to follow its cycle of changes in a a description of the physical features of Saturn ellipse to a straight line, and ultimately disnotion of the reason of this, and of the very vary-reverse order, we may resume the thread of our ing aspect of the rings themselves, presented at description of the discoveries which have been different epochs. Reference to the annexed figure made with regard to the structures of Saturn generally.

will assist our explanation.

FIC.I

OS E

D

Reverting then to the duplicate character of the ring, it will be remembered that it was known to be double as early as 1665, and it is somewhat to the credit of Cassini (when we consider the nature of the optical means at his disposal) that he, ten years later, not only saw the division, but deA tected the difference of tint between the outer and the inner ring, the inner one being the brighter of the two. He compares this difference to that exhibited by burnished and tarnished silver. The next observation of any importance which we meet with in chronological order, is that of Short, the year 1760 would seem to have detected a divithe famous optician and reflector maker, who about sion, or rather divisions, in the outer ring itself. In the month of December, 1823, M. Quetelet thought he saw the outer ring to be double. On was trying a telescope by Cauchoix, in Paris, and December 17, 1825, Captain Kater, employing a Newtonian reflector, by Watson, of 6in. aperture, saw three black streaks, the middle one being the strongest upon the outer ring. One friend with him could perceive several; another one only two. During the following January Kater repeated these observations with a Dollond telescope of the same construction, with which, under equally favourable circumstances, he could sometimes see the lines and sometimes not.

heavens which would enable the student to follow
our description by a direct reference to the object
described. Now, however, that he rises between five
and six in the afternoon, is on the meridian be-
tween nine and ten, and sets an hour or two after
midnight, we propose to give the same amount
and description of detail with reference to him
that we have previously done with regard to other
visible planets; and we will say frankly, in
limine, that it will be wholly our own fault, and
not that of our subject, should this paper prove an
uninteresting one. Premising, then, that Saturn
has an equatorial diameter of 72,250 miles;
in addition to his rings eight moons circulate In it, let S be the sun, the inner small ellipse
about him; and that he is situated at a mean dis- be a perspective view of the orbit of the earth,
tance of 874,321,000 miles from the sun, around and the outer large one of that of Saturn. Then,
which he performs one revolution in 10759-21971 if for simplicity, we imagine these orbits to be
days (or something like 29 of our years), we in one plane, and remember that the axis of
proceed to the more immediate subject of our Saturn, like that of our earth, always travels
paper, the revelations made by the telescope as to through space (practically) parallel to a fixed
the structure and condition of this most marvel- line, we shall see that when Saturn is at A-the
lous object.
earth being (say) at E-we shall see the upper
side of the ring and the north pole of Saturn-a
condition of things which obtains at this moment.
It will be equally evident that when, after an
interval of some fifteen years, the planet arrives
at C, his south pole and the under side of the
ring will be seen. In both these cases it is pretty
obvious that the ring will appear as a broad
ellipse-in fact, at the time of greatest opening,
the minor axis is about half the length of the major.
A little study of the figure will show that, as the
planet travels from A towards C, and from C to-
wards A, the ring will gradually close up, as we
shall be looking at it more and more edgeways; and
that at intermediate points, such as B and D, we
should (with a sufficiently powerful telescope,
and the plane of the ring passing that of the sun)
see only the illuminated edge of the ring as an
excessively narrow hair-like line of light. It will
also be noticed that when the plane of the ring
passes through the earth, or when the sun is
shining on the side turned away from us, the ring,
save on a narrow dark line crossing the planet's
equator, will utterly disappear. Furthermore,
when we reflect how very slowly, relatively speak-
ing, Saturn crawls along in his orbit, it will be
easily perceived that our earth may-and, as a
matter of fact, does-pass twice through the
plane of the ring before it passes the plane of the
ecliptic, so that ordinarily the ring disappears
twice when it is in its ascending and descending
nodes. Under the circumstances of such dis-
appearance the effect presented is that seen

a

Passing over the connection of the Assyrian god Nisroch with the planet Saturn, and the altogether extraordinary circumstance that in many of the Assyrian sculptures this god is represented as surrounded by a ring, we may pretty confidently assert that Galileo was the first observer to whose gaze anything of the remarkable appendage of Saturn was revealed. It was in the year 1610 when he first seems to have made a telescopic examination of the planet. He employed, as is very well known, an instrument of form invented by himself, and called even to this day the Galilean telescope, consisting merely of two lenses mounted in a tube-a convex one for the object glass and a concave one for the eyeglass. Turning this affair, which magnified, however, more than thirty times, upon Saturn, he was surprised to observe that it appeared triple; presenting to his eye the effect of a central globe with two smaller companions in contact with it. Two years afterwards, from a cause presently to be explained, the ring became invisible altogether, and Galileo saw the planet perfectly round. This so utterly puzzled him that he would appear to have persuaded himself that either his instrument, or, as he says, "some demon" had deceived him in his original observations; and, in seeming disgust, to have ceased to regard this particular planet at all. Whether it be so or not, one thing is quite certain, and that is, that Galileo makes no allusion of any sort to Saturn subsequently to the year 1612. Between forty and fifty years afterwards we find Hevelius observing Saturn belowwith great attention. He seems to have got very little further than Galileo, either in what he could see or in his interpretation of it; at least, he finally came to the conclusion that the globe of the planet had two lunules or crescents of hyperbolic curvature, attached by their cusps to its body, the dark sky showing between the inner edges of these crescents and the ball of Saturn. He fancied that a movement of rotation sometimes carried one of these lunules in front of the planet's disc and the other behind it, and so which is a fac-simile of a imagined that he had explained the round phase from our Observatory book, under the date which had proved so great a stumbling-block to of January 25, 1862, and represents the planet Galileo. It was, however, Christian Huyghens, at 12h. G.M.T., as viewed in a 44in. achromatic, who, in 1659, first satisfactorily solved the with a power of 250. As an illustration of the mystery of the planet's aspect in his "Systema return of the ring to visibility, we further append

FIC.2.

drawing copied

divisions, whatever they might be, were not perhas been seen by a considerable number of obmanent. Since then this division of the rings servers, including Encke, Padre de Vico, Lassell, Dawes, and many of less eminence. It may that during the year 1858 and part of 1859, we encourage incipient telescopists if we mention ourselves on several occasions saw this division fairly enough with the same instrument and power that we have employed in making the delineations of the planet which illustrate this paper. It taneously, though Sir William Herschel noticed was never equally visible on both sides simulthat the inner ring became shaded off towards the interior edge; and the late Rev. W. R. Dawes, on a night of exceptionally fine definition, in the set of very narrow concentric bands, getting year 1851, saw this appearance resolved into a darker and darker as they approached the inner edge of the ring. He compared the appearance to that of steps leading down to the dark interval between the ring and the ball. In connection with the two principal bright rings of which we have been speaking, we may call attention to the remarkable fact, that if it be permissible to compare the measures (or estimations) of Huyghens with those of Sir William Herschel, and these again with the refined and accurate ones of the great Russian astronomer, Struve, there can be no possible doubt that a most extraordinary increase has taken place in the breadth of the system within the last 200 years, and that the inner edge of the ring is rapidly and perceptibly encroaching on the space by which it is now separated from the body of the planet. In fact, should this contraction go on at its present estimated rate, it has been calculated that by the year 1980 the dark will be in actual contact with Saturn himself. ring of which we are immediately about to speak

He hence inferred that the

referred, appears of a purple, or rather slateThis interior dark ring, to which we have just coloured tint; it has been discovered within the last twenty years. We say "discovered," albeit

|

In this manner several valuable products were discovered which added greatly to the advancement of the science. I may cite, as an instance, the discovery of vitriolic acid, made at the close of the 15th century by Basil Valentine, a monk of the Erfurt monastery.

These illustrations will serve to show that alchemy was that science which had for its object the formation of those substances which are now considered as having no existence. The mercurial earth of Becker, and the phlogiston of Stahl, which were then looked upon as separate entities, have now been distinctly proved erroneous theories - theories which showed an admirable amount of ingenuity in their construction, but which held no way against truth. Instead of trying to make gold and the philosophers stone, modern chemistry pursues its course in a different direction: it has for its object the study of those elements or particles of matter which come immediately under its notice their properties and their combinations with one another. The chemist works, not as formerly, to isolate or determine the properties of phlogiston and other analogous bodies, but experiments with a view of classification, redacing his experiments to laws which may serve for the guidance of future generations.

there are plenty of indications that it, or at all solution by means of one or other of the several
events a part of it, must have been seen without acids or solvents then known, and the result was
its nature being detected a very long time since. not what was originally expected but some new
The first record we have of it as an unmis- compound, which was immediately designated by
takable appearance is that of the late lamented some fanciful name at the option of the dis-
American Professor Bond, who observing at Cam-coverer.
bridge, in the United States, on the night of
November 11, 1850, with the gigantic refractor of
14-92in. aperture, then remarked that the inner
edge of the inner ring seemed to have a kind of
nebulous margin crossing the ball of the planet as
a narrow belt. The actual shadow of the ring
itself on the ball was seen below the ring. In
total ignorance of what had been observed in
America, the late Rev. W. R. Dawes, F.R.S., on the
night of November 25th in the same year, while
regarding Saturn with an achromatic of 6.4in.
diameter, was struck with a similar appearance.
He repeated the observation on the 29th of the
same month, and again, in conjunction with the
present President of the Royal Astronomical
Society, Mr. W. Lassell, F.R.S., on December
3rd, on which night they both satisfied themselves
of its existence. Oddly enough, news arrived on
the very next day, December 4th, of its discovery
in the United States by Mr. Bond. It may be
somewhat instructive to add, as showing the im-
perative necessity which exists for recording any
new or abnormal appearance, that in the year
1828 this ring must undoubtedly have been seen
in a 64in. Cauchoix achromatic, in the observatory
at Rome; but that nobody seems to have made
any note of it, nor, in fact, to have troubled his
head about it. It was, however, perceived by
Dr. Galle, at Berlin, ten years later; though what
has become of his observations, or rather of their
record, we are wholly ignorant. Assuredly, so
far as Bond and Dawes were concerned, the dis-
covery was quite original. By far the most re-
markable thing in connection with this obscure
ring, however, is that to say nothing of that
painstaking old observer, Schröter, who expressly
speaks of the space on each side of the ball being
as dark, or darker, than the surrounding sky-
neither Sir William nor Sir John Herschel, who
zealously observed Saturn, nor Struve, who
measured the whole of the dimensions of the
planet and his appendages over and over again
with the great 9.6in. Dorpat refractor, ever seem
to have had the least suspicion of its existence;
while, since 1850, it has been seen in one of
Dallmeyer's 3gin. achromatic, and is unmistakable
in any decent telescope of 4in. or upwards in
aperture. It seems difficult to escape the infer-
ence that this strange object must have increased
most remarkably in brightness within the last
thirty years. Dawes, and after him Otto Struve,
thought that the dark ring was itself divided into
two; but this suspicion has not been confirmed,
nor is it quite certain that there is a visible divi-
sion between it and the inner bright ring. Before
dismissing this part of our subject we may say
that astronomers ordinarily designate the three
rings, commencing with the outer one, as A, B,
and C-B being, of course, the broader (and inner)
bright ring, and C the crape ring.

(To be concluded next week.)

INORGANIC CHEMISTRY.

BY GEORGE E. DAVIS,
Honours Certificated Teacher.

[INTRODUCTION.

HEMISTRY, or as it was first termed, alchemy, is a science which we may trace from remote antiquity; and, indeed, its course is more distinctly traced throughout the earlier ages by the fact that the alchemists were supposed to practise what was termed the "black art," and were, in general, supposed to be in league with demons.

In the pictures we have presented to us of these alchemists, their workshops seem to bear a mystic air; the alchemists themselves look grave and dull; whilst the bottles which are ranged upon the shelves are covered with symbols which add more and more to the mystification of the scene. These alchemists worked with salt and mercury, their aim being to produce some hypothetical compound, or to form by some yet unmade mixture the philosopher's stone. Thus alchemy went on: fortunes were dissipated and money spent upon experiments which, although set down by some as utterly worthless, often turned out successful in a different point of view: mixtures were made-they were heated, distilled, cooled, or brought into a state of

A series on inorganic chemistry will not require much introduction to the readers of the ENGLISH MECHANIC. Since the journal first made its appearance ample provision has been made in its columns for notes and queries in the above science; many valuable letters have appeared, and extracts have been made from the various scientific periodicals whenever they have afforded articles likely to be of general interest.

The readers of the ENGLISH MECHANIC have had a series on "Modern Chemical Notation;" symbols have also been thoroughly explained (pp. 49 and 97, Vol. XI.); and as the chemical student should know the elementary facts about light and heat, magnetism and electricity, he cannot do better than follow "Sigma" through his course on electricity.

The present series, which these few remarks are intended to introduce, will be made of a thoroughly practical nature. Chemical technology will be studied in most of its branches-in all those at least which bear upon the subjects of the series; analysis, qualitative and quantitative, (the latter branch will be subdivided into volumetric and gravimetric), will be treated on; and also the blowpipe reactions of the various metals and elements will be inserted in their respective places.

CHAPTER I.

that of heat; this latter force being kept sway a piece of ice tends to retain the form gives by nature or the hand of man.

In the liquid state, such as may be illust by water, the molecules have a tendency te over each other; in fact, they have no pers position, and by the application of heat ther transformed into the third physical for gaseous state. By the application of ha water this force overcomes the cohesion c particles, and also the force of adhesion is « vessel in which it is contained. The steam, and the only visible manifestation ven of its presence is its condensation dr.tv comes in contact with the atmosphere, is itself an invisible gas.

The specimen given above of the war through the three states is not confines pounds; by the application of intense r eury, which is a tuid at ordinary tem becomes solid (at - 39-4° C.), and by this tion of heat it is converted into vapour. boils at 350° C., and emits a coloms one hundred times heavier than hydrog

ELEMENTS, ATOMS, AND MOLECULES. seen that ordinary matter is not capabi » tinuous subdivision; for taking watersw ample, the theoretical division stops reach a molecule. A molecule of the body. smallest group which can take part in mical action. But, although we have rën limit of divisibility as regards water, we cre split up that water-that molecule of water-t simpler matter; its constituents, oxygen hydrogen. By the action of the voltaic batte upon acidulated water it is decomposed, vieliz two gases named above. These gases have ber submitted to the most energetic forces known! the chemist, but without success; at least, in to direction to prove their compound constitution.

We have then divided water and formed a mok cule; this molecule or smallest portion of water which could exist in a free state has been further subdivided, and at last we have reached the ultimate atom. The existence of atoms has often been spoken of ambiguously, and as having rels tion to chemistry alone; but such ideas an totally erroneous. If we believe in the combin tion in multiple proportion we must support th fact by the atomic theory. And, again, wen no chemistry to support the hypothesis-a electricity, and the cognate sciences affor cient proof of its truth.

RADICLES.-The elements, or simpl unite with each other to form compos so doing they exhibit certain de each element in its uncombined extially a simple radicle, having varios force. A group of elements not be but possessing chemical force, is cast 1 * pound radicle; instances are to be s carbonyl C O and sulphuryl S 02"; they as elements, replacing them in many compounds. (See also page 98, Vol. XI..

Chemistry is the science which treats of matter Then, again, the elements may be divi in its many forms; its decomposition into those two great classes-chlorous (electrobodies which are termed elements, and also of and basylous (electro-positive). When atoms; the probable ultimate particles of the pounds are decomposed by the voltaic batz elements as we know them, or as they have at some (chlorous) make their appearance a present been studied: it treats of their properties positive pole, while the basylous appear s and their combinations with one another, where- negative. The most stable compounds are by we are able to form them into groups, the by union of dissimilar elements, whilst s members of which exhibit a strong family likeness. combinations are characterized by their uns Chemistry is truly an experimental science; nature; potassium (basylous) unites with the laws which govern it are the result of exact energy with chlorous oxygen, and the result. and laborious experiments performed by those very stable compound; but when chlorine. men who have devoted a whole life to its study.nitrogen enter into combination, these It is not to be looked upon as an isolated science, chlorous elements are so loosely united that but a branch of one great whole-natural phi- resulting compound cannot safely be touched losophy. The student may begin with chemistry, out danger of causing a fearful explosion. but he will soon find need of a good general knowledge of the cognate sciences-light, heat, magnetism, and electricity.

MATTER, or the bulk of the material world, is at present known to consist of 64 elements, or 64 forms of matter which have not been proved compounds by the most powerful re-agents, or by the most powerful forces which have been brought to bear upon them. The elements are, then, of necessity, simple matter, whilst matter containing several elements is designated compound.

Matter presents itself to our notice in three forms or physical modifications-solid, liquid, and gaseous-which, however, are often not permanent, but dependent upon the forces by which they are influenced. As an instance of the first physical form we may take ice. The molecules in this form keep their relative position unless acted upon by an external force-such as

SYMBOLS, NOMENCLATURE AND FORMULEthe reader will turn, to pp. 49, 97, he will see t a recapitulation on this heading is quite unne sary. The circles will be omitted in gr formule for the future.

ATOMIC AND MOLECULAR WEIGHTS.- A litr hydrogen weighs 0-0896 gramme, which wo has been denominated a crith; a litre of oxy weighs 1-4348 grammes-that is, 16 times hes than hydrogen, or 16 criths. Now, as ed volumes of the simple gases (with a few esc tions) under the same pressure and tempera contain an equal number of atoms, the ator oxygen must be 16 times heavier than that hydrogen.

But the reader will probably say, How are atomic weights of those elements determin which, like carbon, have never been render gaseous? It has been found by experiment :: 35.5 parts of chlorine unite with 1 of hydrog

E

and as 108 parts of silver unite with 35-5 of chlorine, 108 must be the weight of silver. For the determination of the atomic weight of carbon, diamond was burnt in a stream of oxygen; and from the experiments of Dumas, Erdmann, Liebig, and many others, the atomic weight of 12 has been adopted. If the metal be a dyad, the atomic weight is that quantity which unites with 16 parts of oxygen-calcium, for instancethe atomic weight being 40. This refers only to the normal oxides; the higher acid or basic oxides are of course exceptions. The molecular weight is dependent upon the molecular volume, which volume is that which is occupied by two atoms of hydrogen at the same temperature and pressure. The molecules of the monad and triad elements contain two atoms, with some of the pentads-therefore the molecular is twice that of the atomic weight. Most of the artiad elements have a molecular weight which is identical with the atomic; one atom, as in the case of mercury, occupying the same space as two of hydrogen. The molecule of phosphorus vapour occupies half the space of a molecule of hydrogen, if we take two atoms to equal a molecule; but in the above a litre weighs 62 criths, or 124 as the molecule weight, and as other experiments give 31 as the atomic weight, the molecule must enclose four such atoms and remain the normal size. Arsenic resembles phosphorus in this respect.

inferior Welsh coal, treated under this patent, can
be made to yield 15-candle gas. The rationale of
the process appears to be that, whilst in the former
experiments the tar was merely distilled, in this
it is in great measure decomposed, and the
poorer gases coming from the coal combine, while
in their nascent state, with the hydrocarbons of the
tar, which are converted into permanent gases,
instead of condensing and forming obstructions
in the apparatus.

Of all the machinery in general use upon gas works, probably no portion is so uncertain and so unsatisfactory in its operation as that of the ordinary coke "scrubber." In order to extract the tar, the gas after leaving the condenser, was passed through vessels filled with coke or breeze. The transition from these breeze-boxes or tarfilters to "scrubbers" was accomplished merely by increasing the depth, and allowing water to trickle through; but only a small quantity of water being required, the difficulty was to distribute it equally. To meet this, Mr. Hill adapted the well-known " Barker's mill" to the purpose; but even this ingenious contrivance was not sufficient of itself; it distributed the water equally, but the quantity required to keep it going made the resulting liquor too weak to be profitable. Mr. Hills then introduced a " tumbler," a sort of double trough with a division across the centre, and so balanced over an open box that the small stream of water alternately fills first one division and then the other, the division into which the water runs remaining in position until it is filled, when it, so to speak, tumbles over, emptying its contents into the box, thus affording sufficient water to cause the mill to turn for a minute or two, but which stops when the supply is exhausted. Neither the Barker's mill, simple, nor the "tumbler " proved successful, and both have since been discarded. The most common method of filling scrubbers at the present time is with coke; and these seem to answer very fairly provided the gas is free from tar. However, the invention of Mr. Livesey is a decided improvement, and will, in all probability, be universally ACIDS, BASES, AND SALTS.-Acids are generally adopted. It consists in fitting the interior of the formed by the action of water upon the higher scrubber with a number of thin boards, disposed oxides; both are decomposed, and a new compound so as to present, an enormous surface of liquor to results, in which the atoms are very differently the passing gas. In a scrubber 15ft. 6in. diameter arranged. The characteristic of the acids proper by 28ft. high, are placed 22 tiers of boards about is the ease with which they exchange their hydro-1-in. thick; and as there are 258 boards in a tier gen for another basyl. By the action of one the whole surface is about 128,000 square feet. A molecule of water upon an oxide molecule, either layer of coarse cocoa-nut matting is placed on one or two acid molecules may be formed; when the top to spread the water. The gas is passed the latter takes place the acid is what is termed through these scrubbers, the first two being monobasic, that is, contains only one atom of hydrogen replaceable by metals. If, as in the former case, only one molecule of acid is formed by the mutual decomposition of the water and chlorous oxide, a dibasic acid is the result; an acid which contains two hydroxyl radicles, or two atoms of displaceable hydrogen.

The molecular weight of compounds may be found by adding together the atomic weights of the constituent elements, and if the density is required the molecular weight must be divided by the molecular volume; nitric oxide (NO) has a molecular weight of 60, but a density of 15, the volume being 4. As the elements unite with each other in definite parts by weights they also combine by definite volumes or parts by measure; two volumes of hydrogen unite with one of oxygen to form water; equal volumes of hydrogen and chlorine unite to form hydrogen chloride; whilst ammonia gas is composed of three volumes of hydrogen and one of nitrogen.

[blocks in formation]

matter.

the same (as far as the principles of the plane
are concerned) as if the whole thread of the nut
existed. It is obvious that this spreading ont
of the force has the great advantage of much less
pressure on any one part of the screw.
In prac-
tical use it is sometimes the nut, sometimes the
screw that may move, and these motions corre-
spond to the weight forced up the inclined plane,
or the inclined plane forced under the weight.
The apparatus in Fig. 87 may help to make more

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clear the elements of a screw. Standing on the base A is shown one turn, s 8, of a screw. The flat strip of metal, a a a1, wound in a spiral, is the thread of the screw. The cylinder on which a a a' should be rolled is omitted, and in its place a perpendicular plate, bb, supports the spiral. The upright B has two projecting pieces, in which slides the bar C, the lower end of which rests (by a small wheel) on the screw spiral. This bar C represents one portion of the nut, movable perpendicularly. The screw spiral a a a' can move horizontally, being joined to the disc D, which has a pivot p, and lies upon small rollers in the base. A cord c c in the groove of the disc, and fastened at some one point of it, is a convenient means of moving the screw spiral. Lastly, a sheet of paper (No. 2) is cut of the same size and shape as the support b b, and wrapped round the support. Now, to remove all doubt of the spiral a a a' being an inclined plane, it is only necessary to unroll the spiral or its support. The paper sheet being an exact model of the support, is taken off, and when drawn out straight shows an unmistakable inclined plane, which has suffered no change by being rolled height to point. To show the action of the screw upon the nut, turn the disc D in the direction of the arrow. The bar C is forced up. Here is seen by the effect on one bit, what is the effect on the whole nut. Turn the disc in the opposite direction, gravitation forces the bar In the matter of burners, Sugg's "steatite" (the nut) down, and thus besides showing a comand the slit fish-tail are recommended as prefer- mon action of the screw, represents what would The Brönner occur if the bar were subject to the pressure of able to the two-hole fishtail. burner (a kind of split batswing) is reported as the under side of the screw. The bar would be giving an illuminating power of 12 candles, with drawn down apparently, but the real effect would an hourly consumption of 5ft. Indeed, the be the forcing under of an inclined plane having batswing burner has beaten the ordinary fishtaila (not a') for point; in fact, the reverse of what is completely out of the field, as it gives a much seen in the figure, in which a' is the point of the better light with about the same consumption of

plentifully supplied with liquor, and the third with
a small quantity of water. The greater part of
the ammonia is absorbed by the liquor, which is in-
creased in strength to 10oz. or 11oz.; the remainder
is removed in the last scrubber by the use of from
5 gallons to 6 gallons of water to the ton of
coal, or scarcely more than half a gallon to
1,000ft. of gas. The liquor so produced is of
from 7oz. to 9oz. strength, while the
vessel filled with coke would require 3 gallons to
4 gallons more water to the ton, and would only
produce liquor of 3oz. to 5oz. strength; there-
fore the arrangement of thin boards is about
twice as profitable as the use of the ordinary coke

scrubber.

the gas.

same

For some time past numerous gas engineers have been engaged in endeavours to convert the valuable fluids contained in tar into permanent gases. These attempts to utilize the rich hydrocarbons of the tar, however, have hitherto not been so successful as might be desired, principally Some method of completely removing the sulon account of the naphthaline and solid deposits phur from the gas is still wanted, as although its creating obstruction in the mains and pipes, and amount has been reduced to a minimum, there is carbon in the retorts, without the anticipated in- yet sufficient to make its presence felt. creased quantity of gas. An improvement has, however, been introduced at Cork, by Messrs. Hill & Lane, which bids fair to overcome these obstacles.

Their process, which is patented,

SCIENCE FOR THE YOUNG.*

consists in the thorough amalgamation of the tar, BY THE REV. E. KERNAN, CLONGOWES COLLEGE.
with a portion of the coal to be carbonized.
From 30 to 40 gallons of tar are mixed and
ground up with three quarters of a ton of coal and
a quarter ton of breeze. The proportion used is
25 per cent. of the total quantity of coal to be
carbonized. The advantages claimed for the

APPLICATION X.
INCLINED PLANE.
(Continued from page 485.)
ERE the thread of the nut cut away all to
process are a larger yield of gus, increased WE
a small part, and the nut-block still kept
illuminating power, and the re-conversion of the in position, the working of the screw would be
breeze into coke, its particles being cemented
together by the pitch of the tar. It is said that

*All rights reserved.

plane.

This apparatus so far only shows one motion of screw (horizontal) and nut (perpendicular). But it is easy to imagine modifications, by which all the motions of both screw and nut. could be represented. It would be too long to enter into these modifications, and the necessary minutie of detail in describing by diagram might produce confusion in the mind regarding this point (action of the machine), already perhaps too much extended.

III. Conditions of equilibrium. They are to be found in the 4th case of the inclined plane

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Should the divisor 2πr not be understood, it will be quite sufficient for the present to know that it is the mathematical expression of any circumference ; r is the radius, and 2 the relation of the dia meter to the circumference, which not being an

&c.

exact whole number is rendered by the decimal 3.141596. . . . . . From the formula can now be drawn all the conditions of better action, i.e., how P may be as small as possible. It is therefore evident-1st, that the smaller d is the bettersame principle as in the inclined plane; the less the height, the less is P. Hence the closer the threads the more power is gained. 2nd. The greater the radius of the cylinder r, the better same again as in the plane-the longer Hence the larger the body of the screw the better, the pitch remaining the same. 3rd. No gain if (r) be increased in such a way that (d) is proportionally greater. The reason is evident the angle of the plane remains unchanged. 4th. What is gained by the reduction of d is lost in the motion produced. Before the change at each turn, the body could be moved a distance d; after the change it will (it can) only be moved = dn. Practically, therefore, time is lost in effecting the same work. 5th. What is gained by increase of r is lost in accomplishing the same perpendicular work. Recall the principle of "virtual velocities."

=

Now, as the difference may be made indefinitely small, a "working pitch" indefinitely fine can be produced. Great power is gained, but at the expense of time, in consequence of the diminution of space. There are instruments in which the contracting of the space is a gain, as it will be seen in the next application.

SCREW APP. III. THE MICROMETER SCREW.In many optical and astronomical instruments it is necessary to estimate division of space much smaller than those of the most delicate vernier. For this purpose is used the "micrometer screw." The essentials of this instrument are (the frame, nuts, support of r, &c., are left out of the figure), a screw of very small "pitch," A (Fig. 90), and a circular plate B, very delicately divided. The plate is usually joined to the screw-shaft, and as it is moved round, passes under a graduated index r, which points to the number of divisions gone past, and, by its own graduation, indi

cates the number of turns

66

90

which the screw has made. For measurement, it is only necessary to know the pitch" of the screw; the plate will indicate the fractions of that pitch. Suppose then, the "pitch" to be 1 mm., and the plate large enough to be divided into 500 parts. Each turn of the screw moves the body, whatever it may be, to a distance of one mm.; each division of the plate shows 1-500th mm. The number of turns gives the number of mm., and the index r points to the number of 500ths to be added. The micrometer may be made so as to show 1-1000th of a mm. (To be continued.)

The use of the microscope is by no means fined to the discriminations of minerals; with its assistance we may learn many facts, as to the mode of formation of rocks, the order in which the various minerals crystallized, and the alte tions which have been frequently caused by the removal of mineral matter, and its replaceme by another of different chemical composition. L the Rowley rock, the minute crystals of apst penetrate both the felspar and augite: the l also encloses crystals of felspar and magnetis the augite crystallized therefore after the othe had been formed. The olivine contains grains magnetite only, and was probably the second crystallize.

Cases are not uncommon in which crystals h caught up portions of the surrounding mass vi in the act of formation, and other facts ins very clearly the actual condition of the the moment of crystallization. For exam a section of Pitchstone from Planitz, co crystals of felspar, the minute opaque pi thickly scattered through the matrix are together round the sides of the crysta been forced outwards as the latter i size; this clearly indicates that during th tion of the crystals, the matrix was in a nat not in a fluid state, for had the partica quite free to move, there would have be crowding.

In a section of basalt from the Rhine : olivine is in its usual fractured condition, some of the larger cracks have been filled a with the fine crystallized matrix in which th are imbedded; there is no crowding of th particles; in this case, therefore, the olivine wa not only crystallized, but fractured, before the consolidation of the mass. In another section of basalt the crystals of augite and olivine are somewhat rounded, and the cracks filled up, so that they probably existed as crystals or grains

N.B.-In practical use, the power is always
applied to the screw by means of a handle of some
kind. The principles of this handle not having
been as yet studied, it (the handle) cannot here be
made enter into the formula of the screw; but it
is necessary to remark that it may be found in
books as represented by the letter r of the expres-
sion 2 πr. For the present, it is enough to know
that the change of r must make a change in the
value of P, when r in 2 stands for the handle MICROSCOPICAL EXAMINATION OF ROCKS before the ejection of the lava.

with which the screw is to be worked. This consequence, therefore, in no way clashes with the conclusions 2nd and 3rd from the formula where r is the radius of the cylinder (the body) of the

screw.

IV. The uses of the screw, many though they are, can be all included under one head, "the exertion of power (force) of any degree from the smallest to the greatest which the strength of materials will allow." This extraordinary range is in great part effected by the "pitch " of the screw, which can be reduced indefinitely as long as the form of the thread can be maintained uninjured. The applications of the screw are all interesting, and many very important. SCREW APP. I.-WEIGHT REACTION.-In general pitch" is so small that the weight (the force to be overcome) cannot react on the screw when the "power" is withdrawn. Thus, a heavy weight W, Fig. 88, lifted by a screw, cannot push

use the

66

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the screw back, although the power P has ceased to act. The "pitch" (the H of the plane) is so little that the great force of W has but a small "component down along the thread, which component is more than opposed by one of the "obstacles." The detailed examination of the various forces produced by W will afford an interesting study to any one who may wish to see fully the truth of the explanation just given.

SCREW APP. II.-THE DIFFERENTIAL SCREW.After a certain point in various materials the thread cannot resist the pressure upon it-it breaks. There is then the limit of reducing the "pitch." To have a " working pitch" of less height, two screws of different pitch are made to work one into the other (Fig. 89), A, large screw moving as arrrow (a), B small screw moving as a'. On turning the handle P, the screw A advances as its "pitch" requires; but, in the mean time, B is drawn into A to the height of its "pitch;" body W is only moved to a distance equal to the difference between the pitch of A and the pitch of This difference is the working pitch."

B.

66

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AND MINERALS.*

shows that, as a rule, the igneous rocks may be distinguished at once from all others by their structure, which is that of a more or less perfect network of minute crystals: in many cases all the minerals are well crystallized; in others there is an amorphous or glassy base in which they are enclosed; there are, however, other rocks, such as the Felstones and the more recent volcanic Phonolites some of which do not present this crystallized arrangement of their constituents; and then there are the Porphyrites, which are characterized by the presence of crystals of felspar in a compact felspathic base. There is in fact a gradual passage from the compact Felstones to the Porphyrites; so that it appears probable that the amorphous base of all such rocks is simply the silicious magma or paste from which distinct minerals would have separated had the circumstances under which they were formed been favourable for crystallization to have taken place. As a typical example of a widely distributed class of rocks, I will take for description the well known basaltic rock of the Rowley Hills. An examination of thin sections shows that it contains a triclinic felspar, augite, magnetic oxide of iron, a little olivine, and a few crystals of apatite. The felspar is known to belong to the triclinic system, as it exhibits the characteristic strie when examined by polarized light. Augite appears in minute black shining crystals, which appear bright brown, or occasionally green when in thin sections; it cannot be mistaken for any other mineral except hornblende, from which it is distinguished by a marked difference in the angles; it has also a clear glassy appearance, while hornblende is either distinctly fibrous in texture, or exhibits lines or cracks running parallel with the principal cleavage plane. Very frequently hornblende is green, while augite is yellowish brown, but this does not always hold good. The magnetite occurs in minute grains, or as thin lamine, both being black and opaque. The apatite is seen in long acicular hexagonal crystals. The olivine occurs in crystals, and also in irregular grains, of a clear yellowish-green colour; it is, however, rare in this state, being nearly always altered to a dark green mineral. In addition to the above minerals, which must be regarded as the original constituents of the rock, there are also one or two zeolites, calcite, and a chloritic mineral, all of which are found filling cavities, and are secondary formations.

*By S. ALLPORT, from a paper in the Proceedings of the Birmingham Natural History and Microscopical Society.

One of the most important aids in the examination of rocks and minerals is afforded by polar

to discriminate between different minerals, and not unfrequently affords clear evidence of changes which have taken place subsequently to the consolidation of the substance under examination When a thin section of a crystal is placed on the stage of the microscope, and a beam of polariss light is passed through it, the beam is depolariss and generally exhibits colours due to interferes the intensity of colour varies according t direction in which the crystal is cut, al ca quently, in examining a section of mck the various sections of any one mine do not always give the same result; but as the crystals of igneous rocks lie at all angles, it is early always easy to obtain some which, being cat at an inclination to the optic axis, exhibit dift degrees of intensity of action; therefore min which vary much from each other in this re may be easily distinguished.

A most important point to be noted is, that depolarizing action of a crystal is uniform the whole surface of its section, if it consists d one simple crystalline structure; when, howeve the light appears to break up into detached para. each of which changes independently as the analyzer is rotated, we know that it is made of a number of separate crystalline portion either independent of each other, or sometime related as twins.*

A knowledge of these facts enabled me detect the presence of olivine and its pseu morphs in the Rowley rock, as described in former paper, and also in the Geological Man zine, vol. vi., p. 115. A pseudomorph is a mi ral possessing a crystalline form, which does n belong to the substance of which it is composed: it is an altered mineral, or, in other words, aggregate of mineral matter, which has bee deposited simultaneously with the removal of that which possessed the original crystal form it is easy, therefore, to see that the molecula arrangement of the particles must be entirely different from that of the original crystal. Now. by the aid of polarized light, such changes are at once rendered apparent, and we thus possess the means of obtaining most important informs tion on the metamorphism of rocks and minerals of which ordinary light would afford no indication whatever.

Serpentine has hitherto been a great puzzle to geologists, some having regarded it as an intrusive igneous rock, others as of metamorphis

[graphic]

Sorby "On the Examination of Rocks and Minerals, in Dr. Beale's work on the Microscope.

origin. As not unfrequently happens, both are, I believe, right; for every section I have made clearly proves it to be an altered rock, and one specimen from the Vosges mountains contains numerous grains of olivine, in which the change is only partially developed.

These few facts will serve to indicate the importance of this hitherto neglected method of inquiry; for although the pseudomorphism of many minerals has been long studied, little attention has been directed to similar changes in rock masses.

A subject of interest to the microscopical observer, and one of considerable importance to the petrologist, is the occurrence of minute fluid cavities in the minerals of igneous and metamorphic rocks; they have been detected in several minerals ejected from active volcanoes; but so far as I have observed, they are far more abundant in quartz than in any other mineral. Those who wish to examine them may do so by making a section of almost any specimen of granite; they are very numerous in the granite and schorl rocks of Cornwall, the hornblendic granite of Mount Sorrel, in the syenite and gneissoid rocks of Malvern, and in the syenite of Croft Hill, and neighbouring bosses in Leicestershire. In these and similar rocks, the fluid cavities appear to be so entirely restricted to the quartz, that I have not yet detected any in the felspar or mica; they are certainly extremely rare in these minerals, if they occur at all; this, if established, would indicate a difference in the condition under which the minerals were formed, a point which I believe has not yet received attention.

For an account of the curious spontaneous movements of the fluid in some of these cavities, and for other interesting matter connected with the subject, I must refer you to Mr. Sorby's paper already quoted.

During the past summer and autumn (1869) I have collected specimens of the igneous rocks of the Midland coal-fields from the following localities: -- Kinlet and Shatterford, west of Kidderminster; the Clee Hills; Little Wenlock, near the Wrekin, in Shropshire; Coalville, near Bardon Hill, in Laicestershire; and Matlock, in Derbyshire.

A microscopical examination of thin sections shows that all these rocks belong to the same type; they do not in fact differ more from each other than do different specimens of any one of them. The toadstone of Derbyshire is merely an amygdaloidal variety.

The rocks of the Warwickshire coal-field differ considerably from the foregoing; they contain hornblende instead of augite, and are therefore true greenstones or diorites; they may be readily examined in the railway cutting near Nuneaton,

and also a little to the west of Atherstone.

REVIEWS.

The Disposal of Town Sewage. By R. W.
PEREGRINE BIRCH, C.E. London: Spon.
Tsystems in the disposal of the
sewage of towns are examined. Although no
definite conclusion as to the best means of arriv-
ing at that end is adopted, the brochure con-
tains a short resume of the various systems at
present in force, and points out in clear
manner their advantages and defects. The author
was at one time inclined to favour the A B C
system as practised at Leamington, but since he
examined the process at that town has seen
reason to change his opinion. The author has
visited most of the places at which attempts are
made to utilize the sewage, and his conclusions
are doubtless of value. But the fact remains,
that no really unobjectionable method has hitherto
been discovered, and we are no further advanced
than we were some years back-save the negative
information we have derived from the numerous
experiments which have been carried out.

HIS is a pamphlet in which the various

Building Societies and Borrowers; or, Suggestions
for the Consideration of the Royal Commission
on Friendly Societies. By C. D. ARNALDO
FRIEDLEIN. London: Aug. Siegle.

THE author of this little pamphlet clearly exposes
the enormous interest that is really paid by
borrowers from Building Societies under the im-
pression that they are borrowing money at about
4 per cent. Speaking of the system of fines, which
he acknowledges are a necessity to the proper
working of the business of these societies, the writer
says:-"Under the existing system the societies
derive the greatest profit when the borrower falls
into difficulties. Certainly no friendly' society
ought to consider such an occasion a legitimate
source of profit." The fact that a borrower pays
as much interest during the last month of his
term as he did when he held the whole sum, is
sufficient evidence of the necessity for a revision
of the rules governing Building Societies, as well
as a convincing proof of the enormous interest
in reality paid by the customers of these institu-
tions.

Public School Reforms. By M. A. B. London:

L. Booth.

numerous letters which have appeared in the
"M. A. B." has here gathered together the
press on this subject contributed either by him-
self or others. The subject is one of consider
able importance, and deserving the attention of
all interested in the education of the country.
All Vast sums
are annually spent by our public
schools; but the amount of knowledge given for
them does not seem to be of such a character as
might be expected.

the rocks just enumerated are clearly older than the surrounding Permians, which are never penetrated by them.

Having now made upwards of four hundred sections of rocks and minerals, I am inclined to

believe that the following results of microscopical

examination will stand the test of further study. 1. The mineral constituents of the melaphyres and other fine-grained igneous rocks may be determined with certainty-a result which has not been attained by any other method of examination. 2. The mineral constituents of the true volcanic rocks, and those of the old melaphyres, are generally the same. 3. The old rocks have almost invariably undergone a considerable amount of alteration, and this change alone constitutes the difference now existing between them and the more recent volcanic basalts.

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THIS is what might be called a clever attack on modern theology; but there is very little of the calm reasoning of science in it. The author expresses his opinions in too dogmatic a fashion to carry much weight, and his failure to see two sides to a question is ludicrous in the extreme. In his section on 66 Life-how produced in the first instance," after telling us that a dung-heap "actually swarms with living animals," he goes on, "Taking a dead dog, let us pound the carcase in a mill to destroy all life which can be crushed and ground out of it mechanically. Having so done, let us boil the pulp and raise it to such a heat as will destroy not only life, but even germ-life, the life of ova and of seeds, incipient or developed. We have now utterly stamped out every germ of life in the reduced carcase which was once a dog, and to prevent the ance of germs by the air, let us wrap the pulp in cotton wool, which, on the testimony of Professor Tyndall, will effectually exclude all germ-life from without. Here then we have an animal substance from which all life has been crushed out or boiled out, and to which no germ of life can penetrate; what will follow? The mass will putrefy in time, and the putrefying mass will teem with larvæ as before. There cannot be a doubt of it, if the oxygen of the air or water can percolate the cotton wrap." In the first place, ments with compounds of hydrogen and palladium. His wool without allowing the germs floating in the Professor Favre, of Marseilles, has made some experi- how is it possible to wrap this pulp in cotton results point to the conclusion that hydrogen should be

The basaltic lavas of the Rhine and Central France are composel of a triclinic felspar, augite, magnetite, olivine, and frequently apatite, the same minerals as those constituting the old rocks above described. I have fine-grained specimens of the latter hardly distinguishable from recent basalts; and a section of Dolerite from the Puy de Barnère, in Auvergne, does not differ in any important particular from coarsegrained specimens from Rowley. It would be easy to extend the parallelism to other classes of rocks, but I will now only observe that we have here another proof of the doctrine long taught by Lyell the uniformity and continuity of the laws

of Nature.

classed with the metallic elements.

convey

air to settle on it during the operation? And in

the second, how is it proved that all germs are destroyed by the crushing and boiling? The arguments of this gentleman are so radically weak that we can afford to grant him his premises and then be free to reject his conclusions.

RELATIVE MATERIAL STRENGTH OE
FRANCE AND PRUSSIA.
THE Tablet, in an article on this subject, says :-

Tablet, an on this

says.

strength we find a parity between Germany and France. It is curious that in population the two countries are precisely equal. The North German States, count together about 38 millions of souls, Confederation, and its trusty allies, the South German which happens to be the exact figure of the aggregate population of France, as shown by the census of 1866. The several proportions are as follows:The Confederation has 30 millions, Baden about a million and a half, Wurtemberg nearly 2 millions, and Bavaria something under five.

Passing from population to an estimate of economical advantages, there is as little difference between the two countries. Both are two-thirds agricultural; Germany has most ships, and foreign trade, and manufactures; but, as a set-off, French agriculture is most productive. Thirdly, as to revenue from taxation, the total of the Confederation is 40 millions, while that of the States is 12; in all 52 millions. The revenue of France is much larger, but then her national debt is also much larger; so that practically she has but little more than Germany available for all the purposes of her administration. The annual expenditure of both countries on their respective armies, so far as we know it, is about the same, Prussia spends between 12 and 13 millions, France a million more.

There can be little doubt that this war will be

enormously expensive beyond all experience of European wars. Not so expensive, probably, as the conflict between the Federals and Confederates of America, in which a million of men were kept in the field at an outlay of 200 millions sterling per annum. The present outlay will be less; partly because by the conscription a vast saving is effected in bounties and pay as compared with the American system; and partly because the area of the campaign will probably be much narrower. Wars become, in fact, every year more costly as civilization advances. The Italian war of 1859, which lasted only six weeks, cost France at least 20 millions: Bismarck's three weeks' campaign of 1866 cost Prussia nearly as much the present outlay will certainly not be less lavish so that from those figures we may estiImate roughly, and quite within the mark, the probable cost of the present war.

be answered,) what advantage, if any, may be supThe interesting question, of course, is (if it could posed to be possessed by either of the belligerents over the other? On the side of Prussia it may be said that she commences the war with a lighter load of national debt. Her total debt is put down as less than one-third of that of France. Hence her borrowing power is greater. At the same time, as regards this war, the borrowing power of France may, we suppose, be regarded as practically unlimited. The advantage of a small debt is, however, felt in the lightness of taxation; and this advantage Germans are less burthened, and, therefore, comis very decidedly on the side of Prussia. paratively at least, better able to bear additional

imposts.

THE LEAF AS A WORKER.
(Concluded from page 391.)

The

BUT
UT if we regard the leaf only as a drawer of
water, a lifter of earthy matter, a carrier of
lightning, a gatherer of nourishing gases, a defence
against zymotic diseases, we give it an inferior
place it is only a humble, common labourer. Man
might invent and apply machinery to pump the
put on his roof metallic conductors, and can escape
water and evaporate it; he can enrich the soil, can
epidemic diseases if he will breath pure aur.
there's the rub!" for he can get pure air only as the
leaf prepares it for him. Man can, in a measure,
do the work of the leaf, but science has failed to de-
monstrate a way to do the chemical work that the

leaf does.

"Ah!

The leaf is not a common labourer, then; for,

of labour is elsewhere.

Here it

though it deigns to do this drudgery, its great field
of the noblest order, and, as such, performs labour
It is an analytical chemist
that Liebig, and Fresenius, and Regnault attempted
in vain, and such as no chemist gan ever perform.
Here it is that the leaf asserts its superiority as a
worker-becomes a right royal labourer.
uses the same re-agents that man is permitted to
use, but with which he cannot succeed. And so the
leaf looks down upon the great and learned chemist,
and regards him as a bungler. Every exhaled breath
whether arising from the cheerful home fire, from
of man, and of every animal on the face of the globe,
is loaded with poison. The product of combustion,
the fire-box of the locomotive, from the furnace of

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