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and several other elements are monads-that is, they have only one unit of chemical force; carbon, on the contrary, is a tetrad, or possesses four units of force therefore carbon is only saturated, or its affinities satisfied, when it is in combination with four atoms of hydrogen. When two atoms of carbon are concerned, each atom exchanges an affinity; so that six units of force only remain to be saturated. There exist other series in which two or more affinities of the carbon are ex

changed; an instance of such grouping is to be found in the aromatic series of alcohols and hydrides. When a group of atoms exists which shows some degree of chemical force, then that group is termed a compound radical; and its equivalency depends upon the number of affinities which remain unsatisfied. Thus sulphur, which is an hexad, if combined with two atoms of oxygen, is partly satisfied, leaving only two units of force; SO, then, is a compound radical of dyad equivalency.

The marks employed to represent the equivalence of an element or of a compound radical were proposed by Dr. Odling, and are of great use. They consist of dashes or small Roman figures at the upper right-hand corners of the symbols. In the monads they are generally omitted, though in some instances they are used. Thus I' indicates monad iodine; O", dyad oxygen; Au"", triad gold; Civ, tetrad carbon; Nv, pentad nitrogen; and Svi, hexad sulphur.

The elements do not always exhibit the same degree of chemical force. Thus, in hydrogen, sulphate sulphur is evidently an hexad; in several organic compounds it appears tetradic; whilst in the metallic sulphides it acts as a dyad. From this it appears that sulphur has more affinity for oxygen than for most other elements, for under certain conditions it will saturate itself with oxygen, one atom combining with three of the

latter.

Sodium has always been classed as a monad, but Wanklyn (Chem. News, pp. 293 and 313, vol. xx.) tries to make it appear trivalent, a fact which, perhaps, will explain the constitution of some of the so-called double salts.

The equivalence of a radical is expressed by the same means as for an element. The dyad radical ethylene may be formulated thus (C,H)", the two dashes showing its equivalency; (CH) is the triad radical propylenyl, or glyceryl.

Those elements which exhibit an uneven equivalency, such as hydrogen, boron, gold, or nitrogen, are called perissads; and those of even equivalency are termed artiads: specimens of this latter class are to be found in oxygen, carbon, and sulphur.

In graphic formula, of which we shall speak farther on, the atom is demonstrated by a circle containing the initial letter of the element, its symbol; and the equivalence, or chemical force, by projecting lines, each line or connecting link being equal to one unit of chemical force, and generally termed one affinity.

Symbolic formulæ may be of several kinds:a. Empirical.

B. Rational.

y. Typical.

d. Graphic.

E. Constitutional.

Empirical formulæ generally expresses the total number of atoms in the molecule. This is not any, or very little, inconvenience in inorganic chemistry; but when considering organic structure it should be very seldom used: in fact, the system expresses only such data as would lead to the calculation of the percentage composition; it gives no clue whatever to the probable position

of the atoms in the molecule. Hydrogen sulphate is designated by the empirical formula H,SO. This does not tell us whether the oxygen is totally or only partially united with the sulphur; rational will tell us that. Again, the empirical formula for hydrogen orthosilicate is HSiO4; and hydrogen mretasilicate, II SiO: this expresses nothing more than the number of atoms in the molecule.

But

there exists another kind of empirical formula. This modification is not much used in mineral chemistry; it is the formula gained by the ultimate analysis of an organic compound. The same formula is gained in the analysis of metallic salts, when the number of atoms in the molecule ean be further divided. Thus cuprous chloride may have an empirical formula of CuCl, which is a multiple of the real formula Cu,Cl,; hydrogen dithionate, HS,O,, would have an empirical formala of HSO,, which is obtained by calculation

from the percentage composition, but as it is a bibasic acid we know that it must contain two atoms of hydrogen, therefore the true formula is HS,O

1870

replaced by a chlorous element or radical, we obtain an acid.

In calonlating the percentage composition from HO water; } 0

the Empirical formula, we proceed thus:

H, Sa

2

= 64

= 96

162

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The steps of substitution, on passing from water to a metallic oxide, may be seen thus:K Potassium K Į Potassium hydrate K oxide. 162 parts of hydrogen dithionate And the formation of acids:contain 2 of hydrogen, what will 100 contain?

162 parts of the above contain 64 of sulphur, what will 100 contain?

Estimate the oxygen by difference:-100 × 2

And

II

}

H

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H

o water;

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} H hypochlorite

Hydrogen

Condensed molecules of water are taken in certain cases, such as forming the hydrate of a dyad metal, &c.:

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=x, or amount of hydrogen.

H

or

162 100 × 64

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H. He

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Ca

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Ha

H

H

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Rational formulæ gives us some clue to the constitution of a compound, but often this is very slight. It indicates the manner in which a compound is affected when brought under the influence of certain reagents, and as one compound is affected in various ways it is certain that there must be several kinds of rational formulæ for such a compound. Hydrogen orthosilicate may he formulated in either of the following:H(SIO), SiO,(H,O), Siiv(HO); the first expresses the constitution on the binary theoryfour atoms of hydrogen being united to silicic The above are specimens of compounds arradical SiO4, the second shows that it is a com-ranged on the water type, which, though admirpound of water with silicium dioxide, and the ably suited to inorganic chemistry, is not suffi third that tetrad silicium is saturated with ciently explicit when applied to bodies of organic hydroyl. origin; for instance, hydrogen oxalate is expressed :(C2O:)" H2 This does not give us its proper constitution, as the group (CO) exists divided in the molecule, partly saturated with hydroxyl, in the form of oxatyl or carboxyl; the constitution, then, would JCO.HO

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This water type is made to embrace a large number of bodies, as by its means is demonstrated the constitution of all acids and oxides. Wanklyn, however, objects to this on the grounds that such a powerful base as potash can never be formed from such a neutral compound as water. much more basylous radical than the hydrogen view may be correct, but in potash we have a in water; in fact, the hydrogen in water is brought by Odling very near the chlorous elements, as in several places in his Practical Chemistry he writes water as hydric acid. According to Wanklyn's views, the affinities of the oxygen in which holds it on to the chlorous radical being potassoxyl, &c., are completely satisfied, that the affinity of the potassium, which is thereby

saturated.

By giving most of the monad metals and Au Gold metalloids a triadic signification, we are able to Cl, tri-chloride assign a definite formula for most of the double Ptiv Platinum salts, which before had no form of classification Ch tetrachloride A simple substance is under our notice at once, J H2 (Sby Antimony and one which is very familiar alum. This is a Cis "molecule"; Cls pentachloride double salt, formerly regarded as a combination of two sulphates, and called the double sulphate The third type, under which a very numerous of aluminium and potassium. However, there is group of chemical compounds may be classed, is a chloride very similar in it properties, and there the water type. To start from water, by replacing is no doubt that there is a family likeness. We an atom of hydrogen by a positive basyl, we ob- may represent the chloride:tain a class of bodies called hydrates. When we K vili substitute a basyl for the whole of the hydrogen Al contained in the molecule of water, we obtain an Al oxide; when, on the contrary, the hydrogen is K

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Ammonium chloride.

Ammonia. Condensed molecules.

the hydrogen is not in combination with the combination unsatisfied, and these units belong oxygen, which is firmly fixed to the sulphur, but to the sulphur; the two atoms of oxygen, thereis in connection with the feebly-combined atoms. fore, are saturated, and are tightly held to the Ia representing, then, the constitution of hydrogen sulphur, causing the group to act as one atom of sulphate on paper, by the use of a graphic formula, a dyad element; in point of fact, SO is called we must have resource to some method whereby sulphuryl, and it is a dyad radical, and being a we may demonstrate clearly the equivalency of dyad radical it is saturated in hydrogen sulphate the constituent elements. The following is the by combination with two hydroxyl radicals. graphic formula for hydrogen sulphate:

H

H

The organic ammonias of amines are formed from ammonia by replacing an atom of hydrogen by an alcohol radical. Thus, ethylamine is formed by abstracting an atom of hydrogen in ammonia, and inserting the radical ethyl in its place; when two atoms of hydrogen are replaced by an alcohol radical, such as ethyl, then diethylamine is If we regard potassium as a triad element, the formed, and, consequently, when an organic graphic formula would become :ammonia contains three alcohol radicals, it would, as is the case when three ethyl radicals replace hydrogen, be called triethylamine:

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C2H5 N; C,H,N CiH

K

Ammonia.

Ethylamine.

Diethy

lamine.

Triethy. lamine.

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The ammonium chloride formula shows that ammonia has united with hydrogen chloride, whlch is better represented by calling it the chloride of a metallic radical, ammonium, instead of an hydrochlorate of ammonia. The And silver must not be excluded, the sub-or formula shows us the existence of the radical argentous-chloride, instead of being looked upon ammonium united with a chlorous radical, which with doubt, must be regarded as a definite commay be replaced by hydroxyl, then forming pound, in which the affinities of the silver are ammonium hydrate; each atom of hydrogen can tightly held together, so that the molecule easily be replaced by an alcohol radical, forming the yields metallic silver. The following would be the graphic formula for this compound :hydrate of an organic ammonium:

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He H2

H,

H

H2

Ammonium

sulphate.

N2CI

Cuprammonium Platosammo

sulphate nium chloride.

The last type we will consider is the marsh gas type. By its means we can demonstrate the constitution of nearly the whole class of organic bodies. By starting with marsh gas we can, by the substitution of methyl for hydrogen, pass up the series to those members of the group which contain many carbon atoms.

If we take an atom of hydrogen from marsh gas and replace it by the methyl radical, we pass to the next in the series-ethyl hydride; and if we replace another atom of hydrogen by bydroxyl, we pass from an hydrocarbon to an alcohol. Again, by abstracting hydrogen we can form aldehydes; and by adding oxygen to the latter, we form acids. All these changes can be represented by the employment of formulæ on the marsh gas type:

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gas. hydride. alcohol. aldehyde.

Graphic formulæ are seldom seen in any textbook on elementary chemistry, but specimens are given in Miller's Elements Vol. III.; Frankland's Lecture Notes for Chemical Students; and in Buckmaster's Inorganic Chemistry. This species of formulæ is utterly ignored by some chemists; but it must be remembered that it does not intend to represent the actual way in which the atoms are united in a molecule. It is intended to show how the affinities, or degrees of chemical force, are probably balanced. For instance, in hydrogen sulphate there are four atoms of oxygen; but we know they are not all combined with the sulphur with the same degree of force, and we know that

CL

Chlorine, in this case, being a monad. A few instances, however, occur in which it puts forth chemical force equal to a triad.

Silicium, by combining with hydrogen and oxygen, forms an acid called Hydrogen orthosilicate. The constitution of this acid is shown as follows, in a graphic formula :

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it may be considered as fully developed according to the intent of its original design. It has variety and power; it has its five and a half rows of reeds, each row possessing distinct qualities; it has its second manual, by which musical effects valued by the artist may be obtained; is furnished with coupling movement; and is a complete instrument in all that pertains to musical execntion. It is a rival to the pianoforte in the hands of the amateur, and is the "concert-grand" of its class. In making such an allusion we assume that the harmonium we specify is equal in point of workmanship, and is a good specimen of the excellence which skill may achieve in the production of this species of instrument. If the work of an amateur is taken to be the standard, then the harmonium should be placed in competition with a piano of amateur construction. If comparisons are fairly instituted between the cardinal features or characteristics of the two instruments, we have little doubt of the general verdict being in favour of the harmonium on the ground of its superiority as a generator of sounds of varied Icharacter and impressive fulness; setting aside the dexterity of the performers we believe that it has in itself higher capabilities for satisfying the musical susceptibilities of our organisation. Some will smile and say, "Of course you do; personal partiality influences such an expression of opinion." Doubtless, yet how can it be otherwise? Goethe in his mature wisdom, and knowing his own human nature, says, "I can promise to be upright, but not to be impartial." A noble, large-minded utterance; one which all may profitably lay to heart and remember. We cannot be Like will tend to its liking. By our observations free from partiality in judgment and opinion. we would intimate that we who give our attention to the harmonium, that amateurs who devote time and money to the practice or to the construction of the instrument, are driven by an impulse stronger than mere preference or casual fancy; are impelled to do so that we may satisfy an irrepressible longing for qualities of tone, fcr varieties of melodic charms, and sustained and richly-coloured harmony, which we feel the pianoforte is wholly inadequate to supply.

As the representative of its kind, the harmoninın at the point we have reached may be held to be complete, but beyond the ordinary requirements of the musician there is a speciality of demand, to meet which the instrument will have to extend its scope, to take new rank, and invade by consent

The copyright of these letters is reserved by the Author. They were commenced in 94, and continued in Nos. 96, 98, 100, 105, 109, 116, 118, 124, 126, 132, 185,

136, 141, 151, 153, 166, 172, 180, 190, all of which are to be hid except No. 98.

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the province of the organ. Many changes of plan | musician never ceases to covet opportunities f or
and purpose become expedient; to fulfil the duties at his own home.
of its higher state, expenditure on a grander scale
is inevitable, we must set up additional sound-
boards, increase the numbers of the rows of reeds,
provide ampler reservoirs, and lay down a full
scale of German pedals-the pedals, the ambition
of every musician, the organist's own inalienable
estate, the broad dominion of his pride.

"How many rows of reeds can I have in an harmonium?" is the first question that presents itself to the enthusiast who happens to possess a roll of bank notes. It would not be courteous to reply, "As many rooms as you can in a house that you contemplate building," but in truth the whole question is one of expense in relation to comparative utility. If the space to be occupied is limited to a small area, the increased number will 30 cut up and cramp the space that comfort and convenience will be sacrificed. In the attempt to do too much in limited compass or with restricted means, real worth will be swallowed up in display. Everything depends on judiciousness in plan. Additional rows of reeds demand extra space, not

alone for the sake of mechanical facilities of

arrangements, but for their exercise of power. Unless there is ample room for the expansion of tone, a large instrument will be a very lame and impotent affair. Given, space, money and time, skill and experience, and it would be difficult to fix a limit to the musical effects possible to the

harmonium.

Let us restrain ourselves to an average want-namely, an instrument with sufficient volume of tone to afford to the organist a means of estimating at home the character of the music as he will give it upon the organ; that this volume of tone shall be capable of every gradation of light and shade, ranging from pianissimo to fortissimo, and shall be separable in distinct varieties of quality. With the swell manual and the pedals, the harmonium is then qualified for rendering a faithful copy of the organ's music. The additional sound-bound and reeds shall first receive attention. The illustration shows an upper sound-bound with three rows of reeds. These, we think, will fully meet the conditions stated, not too many to be cumbersome by the extra size of instrument they involve, and yet sufficient for the end in view. Four and half rows of reeds on the lower manual, three rows on the upper manual, and two rows on the pedals. Well planned and skilfully carried out, this instrument will possess a grandeur of tone fitting it to be the substitute for the organ, and affording the means of a daily familiarity with the works written for the king of instruments, the practice in which the

to its work with utmost fineness of adjustment The remainder of the mounting of the soundboard corresponds with the method adopted in the horizontal plan. A. toning-leather covers the stems, and beyond that a cover or enclosure of wood, sliding in grooves or fitted in any convenient manner to the sides of the case, and removable at pleasure; this cover may also be fitted with a shutter upheld by a rod connected with a stoprod, when the stop-rod is drawn, the lower end of the lifting-rod being thrown out of the vertical, allows the shutter to open sufficiently to afford greater freedom to the tone. Another arrangement of shutter and a different method of carrying out several details will be given in our next. In t present plan the admission of wind is by trunks at either end of sound-board; by this we save something in depth, a consideration of some moment, though it be only a saving of an inch or two, and therefore we present it first; it has its disadvantages, but then we already have end space to spare, the key-blocks of large instruments being always made wide-from four to six inches, and the amateur can allow this excess in length often much more readily than he can an increase in depth.

Fig. 2 gives a view in section of the soundboard, showing the added length of sound-board and disposition of the wind-way to each register; the whole face of these is covered over when finished. The trunks upward from the valveboard will have to correspond with these. On the top of the trunk each division is to be separately wadded or leathered, to make an air-tight connexion. Below these trunks the admissionvalves are fitted on the under side of sound-board, in the same manner as the valves belonging to lower sound-board, and actuated in a precisely similar way by stop-rods and levers, presenting no complexity for the consideration of the amateur, and therefore needing no further exp anation. It cannot, however, too strongly be pressed upon his attention, that with the enlargement of his aims the tax upon his skill, ingenuity, and patience will increase in compound proportion; A large instru m nt like this will be two feet six various portions of the mechanism each to each, the multiplicity of details, the relations of the or eight inches in depth from frout to back, and to and each again to the whole, will demand from economise space we find it desirable to arrange him great watchfulness, and an accuracy which our plan for an upright sounl-board independent the constructor of smaller instruments is never of the other. To make the addition as an exten- called upon to display. Those who have never sion of the horizontal sound-board we should undertaken such work cannot imagine the amount encroach on ground space to the extent of quite of patience aud sagacity they will be called upon another foot. Few rooms would afford to give up to exercise before they can bring their task to so much space, and not only would the shape of iustrument be disproportionate, but the sound- even an approximately satisfactory condition. board would be too ponderous and clumsy for It may no doubt appear to most amateurs that the handling in tuning and adjusting. Free access building of a large instrument is only a multiplito every part we must have, and with as little cation of the work of small Jones-a question of displacement as possible. So we place it upright time and expenditure which depends solely on his and fix it to a back-board, contriving that it shall own good pleasure. Speaking from experience swing on side-pins or screws, and yet when closed we know differently, and do not say so to disshall press tightly against the back-board, with a courage you in the attempt, but rather to incite roll of wad intervening to make it air-tight, and you to energy and perseverance, under a full also in the same way press upon the trunks which sense of the high task undertaken, and anxious are carried up from the valve-board to meet it. also to give you the assurance that success, when You will notice that there is a side-iron project- achieved, amply repays for all the labour and ing at the bottom of the sound-board, by which it patient care, and thoughtful endurance. Love is screwed to the side of the case. If the height your work for itself, not for the show you can is sufficient to allow the lifting up of lower sound- make of it. board, then this plan may be allowed, but otherwise it will be better to slot or cut the side-iron up to the hole, so that the sound-board shall be capable of being lifted off the screw-pins when requisite to have it out of the way for operations chapter. on the lower portions of mechanism. It can be taken away in a moment when the upper hooks that fasten it are released. The manual itself should be arranged that it may be disengaged, taking with it that portion of the action work which is made a fixture to its frame; this consists of a stout bar and action-rail, with its series of right-angled levers, called "squares," although when shaped they look more like triangles or T will have been noticed in giving the history cranks, each having a spring keeping it down on I of the comet, that from the time of the the resting-rail, which, as you will see, prevents its descent below a determinate level, therefore discovery of its periodicity till its final disappearpreserving the keys to an invariable level, their ance, the name of no English astronomer is own weight of balance to fore-end keeping them mentioned as taking part in the interesting calcuup to their proper contact with the squares; lations connected with it. In the last fact that cloth washers are required, placed between, to prevent noise and abrasion of surfaces, and cloth we have to relate concerning the theory of the also along the rest-rail. The springs, sixty-one comet, however, one of our countrymen has disin number, combined together, will exercise a tinguished himself in no moderate degree. The large amount of pressure, and need that the bar able Superintendent of the Nautical Almanac at and action-rail should be firm enough to be free that, date applied himself to the task of computing from any chance of bending upward by the strain. At the upper arm of each square or an ephemeris of the comet, "the most extensive crank a tapped wire passes through, having a in its plan, and the most accurate in its execution, button on its point, which can thus be screwed up that the world has ever seen.

Of the characteristics which it is desirable the registers of upper manual should possess, whether treated as the correlative of the swell organ or of the choir organ, we shall speak in another (To be continued.)

HALLEY'S COMET.
(Concluded from page 78.)

BY OMICRON.

Valuable as it

will be to the physical astronomer of the present day, it will be much more so to those that shall discuss the observations of the year 1911." With this remark from the lucid account the Astronomer Royal has given of the theory of the comet, in the "Memoirs of the Astronomical Society," and the careful study of which we recommend to every reader, we quit this portion of the subject, and address ourselves to consider the history of the comet previously to the discovery of its periodicity.

As we attempt to trace the comet in the scanty information that ancient chronicles leave us, more and more doubtful do our conclusions become. In 989 and 912, Mr. Hind believes to detect the mention of the comet, but in 837 there is great doubt whet her the comet was seen. However in 760, M. Langier has shown with great probability that a very brilliant comet that appeared in that year was identical with that of Halley; and Mr. Hind remarks that the probability in his opinion amounts to little less than certainty.

From the same source that we derived the picture of the comet as it appeared in 1066, we present a sketch of a comet that was visible in

able one, remarkable for the brilliancy of the can scarcely claim a place in the ENGLISH apparition, and the terror and consternation occa- MECHANIC. The comet at this apparition was The tail of the comet on this occasion is recorded by William of Normandy, and one far-seeing sioned throughout the whole of Christendom. regarded as presaging the conquest of England, to have been upwards of 60° in length, of a monk, probably aware of the expected attack, slightly curvilinear form like the blade of a sabre. apostrophised the comet thus:-"There thon art, Historical readers will remember that at this the source of the tears of many mothers. Long period Calixtus III. filled the papal chair, and since have I seen thee; but I see thee now more that Mahomet II. was at the zenith of his terrible: thou threatenest my country with comsuccess, and Christian Europe threatened with plete ruin."* the inundation of the Moslem power. A brilliant comet appearing at a critical moment such as then prevailed could not be without its influence In order to discover whether the comet has been in an age eminently superstitious. Accordingly observed, or rather noticed, at the times of its the comet was regarded with pleasure or dread, arrival at perihelion, previously to the discovery as the spectator presumed it to betoken success or of its elliptic motion, it will not be sufficient to failure. At Constantinople an eclipse of the examine the meagre records of astronomy, as moon, at the time that the comet was at its they have been preserved to us. Pingré has brightest, drew particular interest to the phenoremarked in his valuable "Cometographie," that menon, and gave full work to the astrologers comets were regarded not as objects to be ob- of the period. A contemporaneous writer thus served, but as signs to be remarked, and to be describes this peculiarity in the heavens:-" Each compared with events; and that in consequence night soon after sunset, a comet was seen like a the history and chronicles of every country and of straight sabre, approaching the moon. The night every age were the most fruitful sources of infor- of the full moon having arrived, and then by mention, and which it was the most essential to chance an eclipse having taken examine. Numerous difficulties beset the patient place, according to the regular proinvestigator of these ancient records. The very cess and circular orbits of the slight distinction that is drawn between comets celestial lights, as is customary; and meteors, the eccentric and ridiculous method some persons seeing the darkness of of describing the appearance presented, the fre- the eclipse, and regarding the comet quent errors that the observers have made in their in the form of a long sword, which rough observations of the comet among the arose from the west and travelled constellations, are a few of the troubles that must towards the east, approaching the be carefully put aside by him that shall attempt moon, thought that the comet in to unravel the mysteries that surround the writings the form of a long sword, thus of the middle ages. Another circumstance that designated with regard to the tends to spread a degree of doubt over the motions darkness of the moon, that the of this comet is the varying degree of brightness Christian inhabitants of the West that it has presented at its different apparitions had agreed to march against the in modern times. In 1682, it appears to have presented a very brilliant appearance, while in 1607, and 1759, the brilliancy was less startling. In 1835, again, it was certainly more conspicuous than in 1759, though less so than in 1682. It is very possible, therefore, that at some of its returns it escaped notice altogether, and although the labours of Mr. Hind appear to trace the comet up to the year 11 B.C., and recognise it at every apparition, great doubt attaches itself to some of the intervening returns to the neighbourhood of the sun. We shall therefore only notice those observations which appear to refer to the comet with tolerable certainty.

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Turks, and would gain the victory;
but the Turks also considering
these things, became not a little
fearful, and had great discussions."
How the Christians argued so as
to augur defeat from the same
cause, history sayeth not, but Pope
Calixtus III. enjoined on all good
Christians a repetition of the Ave
Maria three times a day instead of
twice, and composed a prayer soli-
citing protection from the devil, the

Turk, and the comet. After some months daily | 684, which was the year that Halley's comet
excommunication and cursing the comet waned
away, and finally disappeared, and the terror it
had spread was forgotten, though the deep-
rooted superstition remained as firm as ever.

In 1607, which is the first date of its becoming visible before the time of Halley and Newton, sufficiently accurate observations were made to enable Halley to compute the orbit of the comet It would be to lengthen this paper to a tedious on the Newtonian hypothesis, and it will be and unnecessary extent to follow the history of remembered that this apparition taken in conjunc- the comet through the long interval of time that tion with the one immediately preceding and following, led Halley to make his remarkable prediction. The light of the comet appears to have been "pale and watery," and its course was through the constellations of Ursa Major, Boötes, Serpens, and Ophiuchus. As an instance of the superstition that was prevalent at this period, we may remark that the old chronicles mention among the direful effects that the comet produced "The death of the Duke of Lorraine, and a great war between the Swedes and the Danes.

the industry of Mr. Hind has pursued its motions
and identified its appearances. In 1378 the
comet does not appear to have created any
surprising effect, and its return in 1301 was
possibly unnoticed. The Chinese and Euro-
pean observations, however, leave no doubt as to
its appearance in 1145, when it was visible
nearly two months, from the 15th April to the
19th June. The tail is said to have been 10
long, extending in a north westerly direction.

In the Bayeux Tapestry is to be found the The most careful observer of the comet in 1531, representation of a comet, which there is every was undoubtedly Appian, of Ingoldstadt, and reason to believe is Halley's, though Mr. Hind from his observations Halley has calculated the has found it necessary to advance the longitude elements of the orbit. Appian began to observe of the perihelion 30%, to make the observations the comet on the 13th of August, and appears to accord with the places deduced from the eelemnts have continued his observation till the 23rd. of Halley's comet. We are able to give our Appian noticed that the tail was always turned readers a sketch of the comet as there exhibited, from the sun, and that when the comet's nucleus from Admiral Smyth's "Speculum Hartwelli sank below the horizon, the tail disappeared with anum."

was

a celerity as if some cloud had suddenly obscured it. Appian's observations commence in the constellation Cancer, and are pursued into Leo. The comet is said to have been of a bright golden colour. A contemporaneous writer remarks that on the 25th July, "une poutre de feu " observed, and two comets appeared. The remark evidently refers to a meteor, and we have introduced it to convey some idea of the obscurity in which the accounts are involved, and the necessity of "sifting" the evidence before admitting it as an astronomical fact. It is, however, right to say that Pingré remarks of this author, that it would have been better if he had never written, that he is inexact even in the dates of events that happened in his own time, and that he manifests no extraordinary credulity in everything tending

at the marvellous.

The next previous retura, in 1456, is a remark

Admiral Smyth has given the full picture, in which the terrified courtiers are represented in awe-stricken attitudes, which, however interesting as a specimen of high art of the eleventh century

would have been visible, judging by its period f 76 years. The sketch is taken from the old Neuremberg Chronicle, though, says Admiral Smyth, "from what authority the staid xylographers of that recondite work took it, does not appear."

The identity of Halley's comet with comets of the years 451 and 218, appears very probable. The observations are provided chiefly by Chinese historians of those dates, and the deduced elements exhibit some considerable marks of agreement with the general orbit of Halley's comet. The year 11 B.C, is the most distant date to which Mr. Hind has carried his investigation, and the comet of that year is one of the most certain of the ancient appearances. All the circumstances of the observations are in accordance with the motion of Halley's comet, if the inclination be reduced some 8 or 9°, an amount which the perturbations of so long a period would be quite capable of effecting.

[graphic]

* Pingre, Cometographie.

May we be permitted, for once, more directly to appeal to those of our readers who can afford to give more largely? One of those seasons is now with us when it is especially "more blessed to give than to receive;" and to those who have no other special call on their generosity the ENGLISH MECHANIC Lifeboat affords a fitting object for many an Easter-offering. We do not at all wish to have to beg on behalf of our project; we think better of our subscribers, and believe that next week's list will justify our good opinion. The thousands of our correspondents who so generously afford aid to their fellow-readers which no money could purchase will not, we feel sure, grudge a few pence, pounds, or shillings, according to their means, towards the cause we plead.

PROFESSOR HUXLEY ON THE GEOLOGICAL PEDIGREE OF THE HORSE. N Friday, April 8th, Professor Huxley deli

Royal two bones were fused and

before a very large audience, upon "The Pedigree of the Horse." Sir Henry Holland, Bart., F.R.S., presided.

expresses a wish, which we heartily endorse, that proof which could be given. But it is exceed other only in minute details. But side by side many other subscribers may adopt his plan, and ingly hard to find evidence of this kind good with the remains of the horse in this deposit were that we receive many more subscriptions em- enough to satisfy critical minds, and at present it the remains of another horse-like creature called bodying the results of similar efforts for the cause would be very injurious to bring forward evidence the "hipparion" or "little horse." As much was of "our lifeboat." Another concert in aid of the of a less conclusive nature. But he had one par- known about the hipparion as about the horse. fund will be given on the 21st inst. at Staunton ticular case to bring before them, which he There was no break in the series of time, for both Harold, Ashby-de-la-Zouche, under the patron-thought would stand any amount of worrying, are found in the same deposit. In the fore limb age of the Earl and Countess Ferrers and the and tearing, and pulling about. The case in of the hipparion the leg bones were united, but the Lady Augusta Shirley. This concert has been question was of particular interest, because it con- extra one was traceable, and the leg bones were originated by Mr. George Luff. cerned an animal of which Englishmen were nearer to the average type; the animal also had exceedingly proud, that is to say, the horse. He two little hoofs or fingers, one on each side of the was told that some among his listeners were on main hoof, but they appeared to have been of no the look-out for what are called "tips" in his lec- use whatever. The tooth was still very horsey, ture-(laughter)-but on this occasion he was but it was changed nearer to the ordinary type. going to treat the subject in a thoroughly scien- There was, therefore, in the upper miocene an tific way, and none other. All animals and things animal which resembles the horse in some partiwhich were very accurately and delicately culars, and departs from it in others. Professor balanced were apt to be very beautiful. On the Huxley continued: Did the horse succeed the same principle the beauty of the body of the hipparion? Was it conceivable that the one horse probably has much to do with its being one animal was struck out of existence altogether, and of the best possible pieces of apparatus for run- that the other was then created afresh out of ning swiftly along the land. In many respects nothing? Was it thinkable? If so, be might as the organisation of the horse departed in an ex- well give up his theory altogether. Having protraordinary way from what may be called "the ceeded thus far, the investigator turns with consiaverage quadruped," and the peculiarities to which derable confidence to his geological remains to he desired to call special attention were those of look for the hypothetical ancestor of the hippathe fore limbs, the hind limbs, and the teeth. rion. This ancestor was found in the anchitheWhat was called the "knee" of the horse was in rium, and its remains were found in the lower reality the wrist of the animal. Human beings miocene, but not in the upper as yet, so that there had two bones in the fore-arin, and this was also is a greater gap between the anchitherium and the case with most quadrupeds, but in the horse the hipparion than between the latter and the together into one. In most horses and asses the still more separated; it has three toes in the fore two bones were soldered together, and the shaft limb, the two outside ones beiug half as big as of the ulna nearly disappeared. The horse's hoof the middle toe, so that the foot somewhat resemProfessor Huxley began by saying that time answered to the fingers of the human hand, only bles that of the tapir. This animal, therefore, now travels faster than it used to do. It was now in the hoof some of the bones and fingers of the has the fore foot which theory (requires that it 10 years since he had the honour of addressing a hand were missing, and the horse in reality rests should have. In the hind leg the bones are more public audience on the origin of species and the upon the end of the nail of the middle finger. divided than in the case of the hipparion, the theory of evolution due to the genius of Charles What has become of the other fingers? Two of hinder feet have three toes, and the teeth have Darwin. At that time the theory was passing them were taken away, and two of the other bones not the plasticity of those of the horse, but apthrough the trial, through the struggle for exist- were reduced to little splints, which could be seen proach more nearly to those of the ordinary type. ence, which all youthful organisms in nature from the outside of the horse's foot. This pecu- Thus in these three animals there are proofs of have to undergo. On that occasion he succeeded liarity was found only in these animals. In the gradual progression in teeth, hind legs, and fore so far in overcoming his natural love for peace hind-legs of the horse the small bone was reduced, legs, all the rest of the organisation of each being and quietness-(laughter)-as to advocate what as in the fore-legs, and the middle toe was there horse-like. He submitted, then, that these aniwas then a repressed doctrine. Now all was with its nail made into a hoof. The horse had mals fulfilled the conditions which he laid down changed. The doctrine which then was regularly also a peculiar construction of the grinding teeth at the beginning of his lecture, and that it was refuted and overthrown once in every six weeks of the upper and lower jaw, some portions of these impossible to obtain evidence more complete in had since grown to such an extent that it was now teeth being harder than other portions, so that kind than this of the pedigree and origin of the the leading doctrine of most of the first scientific each tooth wore u nequally in different parts, horse. If a man says that he can trace his podiinen in Europe, and he thought it would be well whereby it always had a rough surface for grind-gree back to the time of the Conquest-well, there to get up a little constitutional opposition to its ing purposes, something like the face of a mill- is no harm in that; but if he says that he is tenets, for now it entered even into the considera- stone. The tooth was composed of ridges and tion of its adversaries. The nineteenth century, pillars, bone and cement, very curiously arranged as far as science was concerned, would be known with respect to each other, and a set of such teeth in history as having given birth to two doctrines made a very efficient mill for the use of the horse. -namely, the doctrine of the conservation of In a very young horse-that is to say, in a horse a force, and the doctrine of evolution as set forth foot long, before it was born-there were the by Charles Darwin. The foundations of the first remains of the ulna much more complete than in of these theories are as firmly set as the walls of the grown animal, and in the young horse the the Royal Institution, but the other is not yet on rudiments of the toes were larger in proportion quite such a stable footing. The doctrine rests than in the adult. Sometimes horses were born upon three pillars of observation and experiment. with extra toes, and there was a specimen of this The first of these is the production. of living mat-kind in the Museum of the College of Surgeons. ter from matter not living; the next is the pro- At the present time also there was a South Ameriduction of new species by natural selection; the can pony in the Victoria Docks with an extra toe third pillar was historical evidence of living ani- to each hoof, and the toes could be felt by the mals succeeding each other in a way which met finger. If these facts were interpreted by the the requirements of the doctrine. When these doctrine of evolution, what did it say? It said three lines of evidence were complete, what was that the missing toes of the horse must have now hypothesis would become theory. As regards vanished from some animal preceding the horse, PROFESSOR TYNDALL ON FILTERED the first of these we were now in an unsatisfac- which had the normal number of toes, and that AIR. tory state; as regards the second, in spite of an the ancestors of the horse must at one time have ROFESSOR TYNDALL has supplemented

enormous accumulation of probabilities, we yet

descended from King Arthur or Noah, the evidence is not worth much. In like manner the history of the horse had been traced by him in the lecture as far back as the Conquest; but he wished to go a little further, and look a little over the edge of certainty, to get some idea of what is lying on the other side. He then pointed out that in the eocene period there are remains of animals which are probably remote ancestors of the horse; the plagiolophus minor to wit. This animal more approaches the rodents in type, but it differs from the horse only in degree, and not in kind. He concluded by remarking that if Darwin's doctrine is made out in this one case of the horse, it is strong evidence that similar modifications have taken place in all cases.

When an abscess is

had the leg and foot bones complete, although PROFFamous lecture on " Dust and Disease." stand without the direct production of a new these were blotted out before the horse was turned species from one common stock; but as regards into a perfect running machine. It also said that In a letter to the Times he describes and defines the third point, which not long since was the at one time the teeth of the horse must have resem--The entrance of air into a wound (he says) is the germ theory of the putrefaction of wounds: weakest of all, it is now, in a sense, the bead stone bled those of other herbivorous animals. It also of the corner, and may be more satisfactorily said that the young or embryonic form often the dread of the surgeon. relied upon than either of the other two. The resembled the common form more than the adult opened he must prevent the air from mingling rocks reveal to us transitional forms between ani- animal did. The extra toe, in some cases, was with the blood-clots if he would avoid putrefacmals now existing and those long gone, and yield probably but a reversion to the type of some remote tion and its teeming accompaniment of animalto the philosopher fossils transitional between ancestor-nevertheless, he did not lay much stress cule life. Some eminent London surgeons inform groups of animals now far apart. At a lecture upon this point himself. Now what did paleon- me that they never squeeze an abscess, lest when delivered at the Institution two or three years tology say to all this? The remains of the horse the pressure is relaxed the air should be sucked ago, he had brought under their notice forms were found in profusion all over Europe and Asia, in. Now, whence this dreaded power? Is it the transitional between the widely spread groups of and they existed in geological strata of enormous air itself that causes putrefaction, or is it somebirds and reptiles; and the reasoning he then antiquity; they could be traced back to periods thing carried mechanically by the air? A foladduced had been rendered stronger by subse- long before any indications of the existence of man lower of Gay-Lussac would affirm the former; a quent observation, more especially by the disco- had as yet been found, yet the horses and asses of heterogenist would refer the animalcules to sponveries of Professor Cooke, of Philadelphia. What that remote period resembled in nearly every taneous generation; a holder of the germ theory was required to form good historical geological respect the horses and asses which now ran wild would ascribe the putrefaction to seeds or eggs evidence? Let A, B, and C be three geological in many parts of Asia and Africa. On going floating in the atmosphere, and which, when sown strata, each successive one older than the other; still further back to the upper miocene period-a upon the wound, sprout into this crop of minute and let X, Y, and Z be groups of animal forms, time when the world altogether differed from its organisms. Do any data exist which will enable succeeding each other. If he could show that present condition as regarded its geographical us to say with certainty which party is right? there was a gradual progression of AX to BY, features-the horse was still found with all its think so. It would be very difficult to redu.. and from BY to C Z, it was the highest kind of present peculiarities, and the two differ from each the purifying power of pure air, even if it exist

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