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part of the mutter forming a nebula ie invisible, we remore the immense difficulty which we otherwise experience in attempting to conceive how nebula; hare assumed or can retain their extraordinary shapes and yet be subject to the law of gravitation.

The researches of Hugging рготе that many of tbe nebula? are gaseous self-luminous masses, whilst the spectra of others prove the existence of solid or liquid matter. These lost being generally those which are most easily resolved, would be those which have been longest in existence, and which, therefore, should contain most liquid and ■olid matter.

The curious shapes of the nebula; are well explained on this theory.

Thus the spiral nebnlie would be produced by two masses of gas rushing together and forming an eddy in which they become mingled with each other. If any detached portion of one gas got mixed up with the other gas, it would be drawn out by the eddy iuto an elongated spiral form, the eurface of which would become visible by the light produced by the chemical action. This would be the kind of nebula which would be produced when the two masses of gas did not differ gTeatly in size, and rushed together in a line not тегу oblique to the line joining their centro of gravity.

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Some spiral nebu'a» consist only of a single

¿ .. whirl. A nebula of this kind

i^ might be produced by a

Lt', small mass of comparatively

¡' dense gas rushing obliquely

fj into a large mass of rarer

'^J& K»'-* Such a moss would

*pF tend to the centre of ¡gravity

of :lm larger mass; and

since those parts which

• i < i- * í are nearest the oentre of

J.aisell, pi., 1. fig. 3.t . Hi

gravity would be moat

accelerated, it would become drawn out into an elongated spiral form.

After a time the whole of the smaller mass of gas will have collected about the ■ centre, and a globular or planetary Inebula will be formed. ,

In the annexed diagram, copied from a drawing by Lasset!, we appear to have a globular nebula in the 'process smaller is shown by

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of formation. That the mass of gas has entered tbe

the fact that

obliquely

ending а Ь of the
tubular portion is
oblique to the axis
of the tube; for
the line а Ъ will
indicate the boundary
of the larger mass.
That the gas is collec-
ting about the centre
of tbe larger mass is
indicated by the fact
that the line о с join-
ing the centre of the
globe with the end of
the tube is perpendi-
cular to a ¿—as it
should be, supposing
the larger moss of a
spherical form Lassell. pi. 2. fig. 9.

-rianetary nebnlœ, consisting of more than one envelope might also be formed in the same way as those having only one envelope, the envelopes being formed in succession at different periods of time.

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Nebula In Lyra,

Annular nebulae might be formed in the following manner. If a small mass [of gas were attracted to a larger masa so as just to graze its surface on passing it, its path (previously parabolic) would become elliptic, and its motion would be changed into a periodical revolution round the larger mass. At each revolution it would Lassell, pL 1- fig- •*• graze the surface of the larger mass, and the elliptic orbit would gradually be changed into a circular one. It would at length come to revolve about the larger moss in snch a manner as continually to graze the surface, and an annulor nebula would be the result.

Those nebulae, like the larger one in Andromeda, in which streaks of darkness cross the bright parts, offer the greatest difficulty in their explanation.

We might imagine that a mass el rare gas has become entangled between two masses of dense gas, and that the masses of dense gas being attracted to one another, crush out the rare gas into a thin sheet, which, looked at edgewise, presente the appearance of a dark streak.

Some of the nebula» of this kind have nuclei ; and it may be remarked that the position of the nucleus, which will be the centre of gravity of the nabula:, is in the position in which we should expect to see it if the apparent vacuous streaks were in reality filled with matter.

Many of the nebula; are very much diffused, and in shape very irregular; but even these show certain characteristics which seem to indicate their mode of formation. The extreme faintnessof their light favours thehypothes» that they are not luminous throughout, but that their lumi

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ЬавагП, pi. 5. fig. 21.

nosity occurs only here and there in comparatively thin shells.

Again, if these nebnlie were luminous throughout, the intensity of their light should be greatest where the thickness of matter looked through is greatest, and should fade away at the boundaries, whereas, if the visible parts occurred in shells, the boundaries should appear brighter than other parts; for at the boundaries the line of sight would be very obliquo to the shell, and a greater thickness of luminous matter would be looked through. Now if we examine any of the irregular nebulao;, we see some parts of it ending abruptly with a clearly-defined outline, whilst in other parts the light gradually fades away into darkness. We may suppose that in the one case we are looking edgewise at a shell, so that the line of sight is tangential to ita surface, whilst in the other caso we ore looking nt a part where the lummous shell gradually thine out. Now in the first case we find that the light increases towards the border, consistently with the supposition that the visible parts are iu thin shells.

This peculiarity is, I apprehend, what Professor Bond and Mr. Lassell refer to when they speak of the scroll-like appearance of the nebula in Orion.

In those nebula; which appear to have assumed a more stable form, as in the elliptic and circular nebula), the light diminishes from the centre to the circumference.

These nebula) may be in a later stage of formation; they may have become more condensed, and a more intimate mixture of the gases may have taken place, and iu consequence they may be more or less luminous throughout. Thuir shape, and the fact that they are generally resolvable in the telescope, point to the conclusion Jthat they have been a long time in existence.

Before turning to the sutiject of oometa, I may remark that the theory that there are large masses of invisible gas traversing space, affords an explanation of the sndden temporary outbursts in the intensity of certain stars. Such an outburst might occur if a star became enveloped with a mass of gas with which it could chemically combine.

It also explains the phenomena of periodical stars. Mr. Hnggins has found that the diminution in the intensity of the light of these stars is due to an increase in the number and size of the absorption bands in their spectra.

It has already been suggested that large opaque bodies may be revolving in orbits round such stars, and periodically obscuring their light. We have only to suppose that large masses of invisible gas instead of opaque bodies revolve about them, to explain the phenomenon iu accordance with spectroscopic observation.

(To be concluded next meet.)

FRICTION IN STEAM CYLINDERS.'
Вт Mb. P. Jensew.

SO few data exist on the subjeot of friction in steam cylinders, tbat the author approaches it with some diffidence, more especially as he has not had time to make direct and comprehensive trials which would furnish particulars for exhaustive treatment of the subject. He, therefore, can only offer such remarks and make such deductions from the experience of others and of himself that have a bearing on the subjeot, without assuming to eettlo questions relating thereto. Of the importance of the subject there can be no question, as engineers are awareof the great percentage of power that may be consumed in piston friction. Hence it is well to define this loss under various circumstances, and then to apply remedies for diminisbing the loss. Friction in the steam cylinder may be classed under three heads; piston friction, slide valve friction, and stuffing box friction. As regards piston friction it ought to depend upon the working pressure, the packing material employed for keeping the piston tight, the extent of the rubbing eurface of the packing, and the means of lubrication. It is evident that a piston should not be made to stand a higher pressure than that it is intended to work with, otherwise a great amount of power may be lost by unnecessary friction, and wear and tear both of piston and cylinder will ensue. It also appears evident that eogines expanding the stonrn to any great extent in one cylinder should have piston packing, the tension of which is dependent upon and constantly varying with the pressure of tho steam at any part of the stroke. There is not, it is believed, any difficulty in this, and all are doubtless familiar with one or more constructions of pistons of this sort which answer the purpose in a greater or less degree.

The common rough and ready way of calculating piston friction by assuming a certain constant pressure per square inch of piston as being the measure lor the piston friction (which, as will be seen presently, constitutes by far the greater portion of the total friction) of the engine itself is erroneous, or at any rate should be used with discrimination. Although it has been found in a fow instances that the friction of a piston for instance in an engine working with 2J atmospheres may be expressed by (say) 21b. per square inch of the piston, which may or may not mean that the piston packing has had just the requisite amount of tension, and not perhaps 50 per cent, more than requisite, we have no right to infer tbat the same rule holds good with 5 or 10 atmospheres pressure. If the piston packing has just the right tension, the friction must amount to a certain percentage of the pressée. But we must not lose sight of another circumstance—namely, that the circumference of a piston increases as the diameter simply, while the area increases as the square of the diameter.

Ths question is, has a piston of 24in. diameter double the amount of friction, or has it four times the amount of that of a 12in. piston, other circumstances beinç alike, that is, with the same material, same depth of packing, state of lubrication, pressure, &c. We must not forget either that the proportionate depth of packing vnries with tho diameter of the cylinder. Whether it is supposed to give less wear on tho piston rings (an opinion considered iucorrect by the author) or not, we need not stop to disenss ; the practice is, however, not to increase the depth in direct proportion as

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the diameter of the piston increases in size, and thus it is that the piston friction does not in practice decrease in the ratio otherwise anticipated, though it is believed that it does decrease. In other words.it is propounded that piston friction us percentageofpowerdecreasesasdiameterinoreaees, tint increases as pressure and depth of paokiog increase, the packing material beiogthe same. In practice the following rule holds good :—Depth of packing = $ <Jd in inches : for instance, for a 19in. cylinder, depth of packing = t X 7 = 6$; for smaller engines, }'JV d (say) 16in. cylinder, depth of packing = J X 4 = 2|in. This is for cast-iron packing rings. With Ramsbottom's steel ringsa mach smallerdepth is found quite sufficient. Hence if it is found that 21b. per square inch is the measure of the piston friction in a 12in. cy linier, it would seem that the friction of a 24in. cylinder (having four times the area but only double the diameter), wculdonly be double, bnt ns the depth of packing is as 23 to 389 it would 389

become X 2 = 3-38, so that the pressure per

2-3 square inch absorbed bypistonfriction would becomo 338

•> x = l'GOlb. per square inch in a 24in.

4 cylinder, and 21b. in a Win. This is of course assuming the ordinary theory of piston friction to bo correct, namely, that it is to be calculated by the superficial area of the piston packing x the pressure of the steam X the friction, co-efficient. If, theo, tho above be correct, it is dear that we must avoid taking a certain fixed percentage of the pressure on tho piston area as the measure of the piston friction, except we take the size of the cylinder into acoount.

The packing material has considerable inflanece on the friction. Hemp packing for moderate and for high pressure сапеез more friction than metallic packing, which is now almost universally adopted. Cast-iron rings or Ramsbottom'e steel rings, though not giving so little friction as gun metal, are generally preferred, because thoy wear well and are not so much affected by grit. The author's experience is that Ramsbottom's rings are tight, wear well, and do not require excessive tension. For great expansion in a single cylinder the tension of the packing should bo dependent npon the varying pressure in the cylinder, its before stated.

In considering the question of staffing box friction, the author would first observe that tho amount of loss caused by it is only trifling if the packing is in proper condition and the gland has been properly fitted; bnt otherwise this loss may become enormous. The author is not aware of any comparative experiments showing the frictiou caused by the employment of varions kinds of stuffing-box packing, although that, doubtless, has also a great influence. But what all are awaro of is the great wear on the piston rod through having the packing too hard. A careful engine driver avoid this, but every engine driver is not careful, and if he has many other things to look to, as is often the case, then tho plain question arises whether it is not better either to use a packing that requires but little lubrication, or else to provide means for keeping the packing continuously supplied with a very Blight amount of grease, which, as experience has shown, can be effected by greasing the steam before entering the cylinder. No other means are then found necessary for lubricating the slide rod or piston rod, and hard packings becomo an impossibility.

It is not intended to describe the various kinds of packing; suffice it to say that there are sonio . which answer their purpose very well, pome of them requiring little or no lubrication. The selflubricating mineral packing has under some circumstances answered very well. Metallic stuffing box packing has been proposed and used. On account, however, of the great depths required aud the expenso and trouble attending its manufacture, it has never come into extensive use. Metallic stuffing-box packing would bo a great lioon, provided it answered its purpose. Mr. John l'enn used to have one of his small shop engines fitted with metallic stuffing box packing, and the author believes ho has so now.

(Го be continued.)

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HINTS ON THE SELECTION AND U3E OF A MICROSCOPE.

THE quality of a microscope, says the Technologist, of course depends entirely npon the perfection with which it shows objects as they really are. Some microscopes distort objects so as to give views that are anything but correct. Others colonr whatever they show with all the brilliant hues of the rainbow. We have often admired the magnificent colours displayed by natural objects under the microscope, such, for example, as the petal of the geranium, whose cells are rilled with the most brilliant scarlet colouring matter; or the crystals of the ruby oxide of copper, which are gorgeous beyond expression ; or various objects seen by polarised light, which gives to ssme of the most colourless and transparent crystals colours that far excel the tints of the ruby or the sapphire; bnt we have often smiled when asked to view the splendid colour shown by hair, or a fly's eye, or a section of wood seen by ordinary transmitted light, for we well knew that these object« have no colour of their own, or at least only dull, neutral tints, and that all the gorgeous hues so lavishly displayed were merely the result of defects in tho microscope.

It is nnqaestionably true that one ot the fine larga achromatic mioroscopes, furnished with ob-' jectives of low as well as high power, would be the best for all purposes of examination. But such microscopes are very expensive. A tolerable one cannot be had for less than one or two hundred dollars, while a first-class one will cost four or five times that amount. Such a microscope, although desirable, is not absoln'ely necessary, and therefore we will turn our attention to the less costly kinds.

The first that presents itself is the simple lens mounted in a metal or horn frame. In the hands of a skilful observer, this instrument will do good service. Opticians frequently arrango several lenses in one frame, and suggest the idea of combining them so as to obtain an increase of power. In general, however, this idea is fallacious, and the instruments are not properly arranged for tho purpose. In the first place, there is no diaphragm (or thin plate with a small hole in it) between the lenses to cut off the extra light; and, in the second place, the lenses are placed as close to each other as possible, so as to occupy but little room, and this prevents us from obtaining a good effect. Moreover, it is unfortunately true that opticians (somebody ouce called them in derision shopticiaus) rarely give ns the best selection ofpowers. There is too much sameness in them. The best arrangement we could find in a large enlloction consisted of three lenses, whose magnifying powers were respectively 25,20, and 16 diameters. Now, this is not variety enough, and the reason for not making a greater difference between the powers of the Tenses is the fact that high powers are so much smaller than the lower powors that to combine them in the same frame makes a clumsy instrument. We confess, however, that we would much prefer efficiency to elegance.

A framo containing three plano-convex lenses, lin., tin., and ¿in. focus, we have found altogether the most convenient arrangement. The magnifying powors are 10, 20, and 40 diameters ; and whether wo desire to examine a mineral, a flower, or an insect, whether we wish to look at the mildew on a grape-leaf or the beetle which preys upon the buds, such a series of powers will enable us to do so thoroughly.

In selecting single lenses to be used as microscopes, procure, if possible, those of which one side is perfectly flat, that is to say, plano-convex. The view obtained by such lenses is always better than that given by donble convex lenses of the samo power. Such simple microscopes are undoubtedly the best cheap instruments. But at a very slightly higher cost we may obtain that best of all simple microscopes—Wollaston's doublet. This microscope is formed of two planoconvex lenses adjusted together in the same tube. It is rsjely that we con find a good one in the opticians' stores, but they are so easily mounted that any working optician could put one together at short notice. One of our friends made a remarkably efficient instrument of this kind, having formed the lenses of plate glass (a piece of broken store window), which consequently did not require the plane side to bo ground, and arranged the lenses in a tube made of stout writing-paper, pasted. Suitable lenses could, no donbt, be procured by mail from most opticians, and it would no doubt require no great mannal dexterity to mount them.

ON THE RELATIONS BETWEEN BODY

AND MIND.«

Lbotubs II.

(Continued from page 243.)

IT is a natural question. Whence come these animal traiU and instinets in man Í Wbenc e was derived the instinct which taught, the idiot woman to gnaw through the umbilical cord? Was it really the reappearance of a primitive instinct of animal nature—a faint echo from a far distant past testifying to a kinship which man has almost outgrown,orhas grown too prond to acknowledge? No doubt such animal traits are marks of extreme human degeneracy, bnt it is no explanation to call them so ; degenerations come by law, and axe as natural as natural law can make them. Instead of passing them by as abnormal, or, worse stilL stigmatising them as unnatural, it behoves u» to seek for the scientific interpretation which they must certainly have. When we reflect that every human brain does, in the course of its development, pass through the same stages as the brains of other vertebrate animals, and that its transitional states resemble the permanent forms of their brains ; and when we reflect further, that the stages of its development in the womb may be considered the abstract and brief chronicle of a series of developments that have gone on through countless ages in nature, it docs not seem so wonderful, as at the first blush it might do, that it should, when in a condition of arrested development, sometimes display animal instincts. Summing up, as it were, in itself the leading forms of the vertebrate type, there is truly a brute brain within the man's ¡and when the latter stops short of its characteristic developement as human —when it remains arrested at or below the level of an orang's brain, it may be presumed that it will manifest its most primitive functions, and no higher functions.

I am not aware of any other considerations than those just adduced which offer even the glimpse of an explanation of the origin of these animal traits in man. We need not, however, confino our attention to idiots only. Whence come the savage snarl, the destructive disposition, the obscene language, the wild howl, the offensive habits, displayed by some of the insane Î Why should a human being deprived of his reason ever become so brutal in character as some do, unless he has tho brute nature within him? In most large asylums there is one, or more than one, example of a demented person who trnly ruminates : bolting his food rapidly, he retires afterwards to a oorncr, where at his leisure he quietly brings it up again into the month and masticates it as the cow does. I should take up a long time if I were to enumerate the various brute-like characteristics that are at times witnessed among the insane; enough to say that some very strong facts and arguments in support of Mr. Darwin's views might be drawn from the field of morbid psychology. We may, without much difficulty, trace savagery in civilisation, as we can trace animalism in savagery; and in the defeneration of insanity, in the unbinding, so to say, of the human kind, there are exhibited marks denoting the elementary instincts of its composition.

It behoves ns, as scientific inquirers, to realise distinctly the physical meaning of the progress of human intelligence from generation to generation. What structural differences in the brain are implied by it? That an increasing purpose runs through the ages,and that "the thoughts of men are widening with tho process of the suns," no one will call in question; and that this procese has been accompanied by a progressive development of the cerebral hemispheres, the convolutions of which have increased in size, number, and complexity, will hardly now be disputed. Whether the fragments of ancient human crania which have been discovered in Europe do or do not testify to the existence of a barbarons race that disappeared before historical time, they certainly mark a race not higher than the lowest surviving human variety. Dr. Prichard's comparison of the skulls of the same nation at different periods of its history led him to the conclusion that the present inhabitants of Britain," either as the result of many ages of great intellectual cultivation, or from some other cause, have much more capacious brain-cases than their forefathers." Yet stronger evidence of a growth of brain with the growth of intelligence is famished by an exami

• Two lectures delivered at the Royal College of Physicians In 1S70. By Heurt Maddslet, MP, F.IIC.P., Professor of Medical Jurinprudenoe In University College, London.

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ostión of the brains of existing savages. Gratiolet has figured and deacribod the brains of the Hottentot Venus, who was nowise an idiot. He found a striking simplicity and a regular arrangement »f the convolutions of the frontal lobes, which presented an almost perfect symmetry in the two hemispheres.'involuntarily recalling the regularity and symmetry of the cerebral convolutions in the lower animale. The brain was palpably inferior to that of a normally developed white woman, and could only be compared with the brain of a white idiotic from arrest of cerebral development. Mr. Marshall has also recoutly examined the brain of a Bushwoman, and has discovered like evidence of structural inferiority: the primary convolutions, although all present, wore smaller and much less complicated than in the European ; external connecting convolutions were still more remarkably defective ; the secondary sulci and convolutions were everywhere decidedly less developed ; there wa-i a deficiency •of transverse commissural fibres ; and in size, and every one of the signs of comparitive inferiority, 41 it leaned, as it were, to the higher quadrunianous forms." The developmental differences between this brain and the brain of a European were in fact of the same kind as, though less in degree than, those between the brain of an ape and that of man. Among Europeans the average weight of the brain is greater in educated than in uneducated persons ;its size—other circumstances being equal—bearing a general relation to the mental power of the individual. Dr. Thurnam concludes, from a eerie« of oarefullj-compiled tables, that while the average weight of the brain in ordinary Europeans is 49 onnces, it is 64-6 ounces in distinguished men; and Professor Wagner found a remarkably complex arrangement of the convolutions in the brains of five very eminent men which he examined. Thus, then, while we take it to be well established that the convolutions of the human brain have undergone a considerable development through the ages, we may no less justly conclude that its larger, more numerous, and complex convolutions reproduce the higher and more varied mental activity to the progressive evolution of which their progressive increase has answered—that they manifest the kind of function which has determined the structure. The vesicular neurine has increased in quantity and in quality, and the function of the increased and more highly-endowed structure is to display that intelligence which it unconsciously embodies. The nativo Australian, who is one of the lowest existing savages, has no words in hie language toexpress such exalted ideas as j ustice, love, virtue mercy ; he has no such ideas iu his mind, and cannot comprehend them. The vesicular neurine which should embody them in its constitution and manifest them in all its function, has not been developed in his convolutions; he is as incapable, therefore, of the higher mental displays of abstract reasoning and moral feeling as an ■idiot is, and for a like reason. Indeed, were we to imagine a person born in this conntry, at this time, with a brain of no higher development than the brain of an Australian savage or a Bushman, it is perfectly certain that he would be more or less of au imbecile. Aud tho only way, I suppose, in which beings of so low an order of development could be raised to a civilised level of feeling and thought would be by cultivation continued through several generations -, they would have to undergo a gradual process of humanisation before they could attain to the capacity of civilisation.

Seme who one moment own freely the broad truth that all mental manifestations take place through the brain, goon, nevertheless, to straightway deny that the conscience or moral sensibility can be a function of organisation. But if all meatal operations are not in this world equally fonctions of organisation, I know not what warrant we have for declaring any to be so. The solution of the much-vexed question concerning the origin of the moral sense seems to lie in the considerations just adduced. Are not, indeed, onr moral intuitions results of the operation of the fundamental law of nervous organisation by which that which is consciously acquired becomes an unconscious endowment, and is then transmitted as more or less of an instinct to the next feneration? Thev are examples of knowledge which has been hardly gained through the suffering and experience of the race being now inherited aa a natural or instinctive sensibility of the well-sonstituted brain of tho individual. In the matter of our moral feelings we are most

truly the heirs of the agee. Take the moral sense, and examine the actions which it s motions and those which it forbids, and thus analyse, or, as it were, decompose, its nature, and it will be found that tho actions which it sanctions are those which may be proved by saber reason to be conducive to the well-being and the progress of the race, and that its prohibitions fall upon tho actions whioh, if freely indulged in, would lead to the degeneration, if not extinction, of mankind. And if we could imagine the human race to live back again to its earliest infancy—to go backwards through all the scones and experiences through which it has gone forward to its preeont height—and to give back from its miud and character at each time and circumstance, as it passed it, exactly that which it gained when it was there before,—should we not find the fragments and exuvise of the moral senso lying hero and there along the retrog\do path, ami a condition at the beginning which, whether simian or human, was bare of all true moral feeling?

We are daily witnesses of, and our daily ootions testify to, the operation of that plastic law of nervous organisation by which separate and successive acquisitions are combined and so intimately blendei as to constitute apparently а single and undecomposablo faoulty: wo observe it in tho formation of our volitions; and we observe it, in a more simple and less disputable form, in the way in which combinations of movements that have been slowly formed by practice are effected finally as easily as if they were a single and simple movement. If the moral sense —whioh is derived, then, msomuoh as it has boon acquired in the prooess of human development through the ages—were not moro or less innate in the well-born individual of this age, if he were obliged to go, as the generations of his forefathers have gone, through the elementary process of acquiring it, he wonld be very much in the position of a person who, on each occasion of writing his name, had to go through the elementary steps of learning to do so. The progressive evolution of the human brain is a proof that we do inherit as a natural endowment the laboured acquisitions of our ancestors; the added structure represents, as it were, the embodied experience and memories of the race; and there is no greater difficulty in believing that the moral sense may have been so formed, that in believing, what his long beon known and is admitted on all hands, that the young fox or young dog inherits as an instinct the special cunning which the foxes and the dogs that have gone before it have hod to win by hard experience.

These remarks are not an unnecessary digression. Nor will they have been made in vain if they serve to fix in our minds the conviction that the law of progressive evolution and specialisation of nerve-centres, which may be traced generally from the first appearance of nervetfssue in the lowest animals to the complex structnro of the nervous system of man, and specially from the rudimentary appearance of cerebral convolutions to the numerous and complex convolutions of the human brain, does not abruptly cease its action at the vesicular neiirine of the hemispheres, but continues in forco within the intimate recesses of the mental organisation. Moreover, they are specially to the purpose, seeing that they enable us to understand in some sort how it is that a perversion or destruction of the moral sense is often ono of the earliest symptoms of mental derangement: as tho latest and most exquisite product of mental organisation, the highest bloom of eultnre, it is the first to testify to disorder of the mindceutres. Not that wc can deteot any structural change in such case; it is far too delicate for that. Tho wonder would, ind-ed, be if we could discover such more than microscopical changes with the instruments of research whioh wo yet possess. Wo might almost as well look to discover the anatomy of a gnat with a teloscope.

(To be continuad.)

GRINDING EDGE TOOLS.

EDGE tools aro fitted up by grinding, very much as a plank would tie reduced in thickness were » large plane employed, in which were set a hundred or more very small gouges, each cutting a narrow groove. The sharp grit of the grindstone being harder than the iron or steel, cuts very small channels in the surface of the motal, and the revolving disc carries away all tho minute particles that aro detached by the grit.

If we were to examine the surface of a tool that has just been removed from a grindstone, under tho lenses of a powerful microsoope, it would appear, as it were, like the rough surface of a field which has recently been scarified with some implement whioh formed alternate ridges and furrows. Hence, as these ridges and furrows run together from both sides, at the cutting edge, the newly-ground edge seems to be formed of a system of minute teeth, rather than to consist of a smooth edge. For this reason, a tool is first ground on a coarse stone, so as to wear the surface of the steel away rapidly; then it is polished on a wheel of much finer grit; and finally, in order to reduce tho serruture as much as possible, a whetetouo of the finest grit must be employed. This gives a cutting edge having the smallest possible serration. A razor, for example, does not have a perfect cutting edge, as one may perceive by viewing it through a microscope. And yet the serrations are actually so much smaller than a human hair that the minute teeth cut the hair in twain; but when the serrations on the edge of the гагог becomes so battered up and dull that they will not sever a hair, or cut a man's beard off, the edge must be houed and strapped until the system of minute teeth will be во much smaller than a hair that sevrai of thorn will take hold of the smallest hair at once. These suggestions will furnish something of an idea of the operation in grinding aud whetting edge tools.

Beginners are sometimes instructed, when grinding edge tools, to have the stone revolve towards the cutting edge, and sometimes from it. When the first grinding is being done it is a matter of indifference whether this is done or not; but when the finishing touches are applied near and at the very edge, a grinder can always comptete his task with more accuracy if the periphery of the grindstone revolves towards tho cutting edge, as the steel that is worn away will bo removed more easily; whereas, when a stone runs in the opposite direction, the grinder cannot always toll exactly when tho side of the tool is fully ground up to the edge. This is more especially true when the steel has a rather low or soft temper. The stone, when running from the edge, will not sweep away every partióle of tho metal that hangs as a "feather;" but when the stone revolves towards the edge there will be no "feather edge " to deceive the eye of the grinder.

WATSON'S DEEP TUBULAR WELLS(Illustrated on next page.)

THE advantages claimed for Mr. Watson's system of obtaining water or other fluids from any depth, over any other method, will be easily understood by our scientific readers from the accompanying cuts, with but little explanation of the details; its utility in boring through a hard or rocky soil being more particularly prominent.

In sinking or boring by this method, in ordinary cases, the first length of tubing is provuTëT with a fluted steel penetrator, having a groove cut in the part fitting into the tube, so as to ailcw it to revolve on the screwe in the lower end of the pipe, which is made stronger for the purpose. The spindle for carrying the weights need in driving down is provided with a collar, tho lower side of which forms a fair surface to fall on to the brass hand nut, which is screwed on to the upper end of the tnbe, so that it is not injured by the blow, and when down to the surface of the soil this nut is removed and another length of tube conneoted with an ordinary socket joint, as shown i nthe cnt, the process being continued as before, and tubes added as required. In boring through а rocky soil a double tube is used; the outer tube at its lower end has a steel collar fluted on the outside, aud also revolving at each blow of the weights in a similar шацпог to that in the foregoing.

The inner ube is providod with a steel point likewise constructed to revolve, as in the first instance of the single penetrator, but has, in addition, two recesses to suit the two catohes or tumblers fitted in tho revolving collar of the outer tub.1, which keep it in its proper position, without impeding its withdrawal when necessary. The two tub'.-sore of equal lengths, fitted with brass hand-nuts at the upper ends, similar to that on the single tube, thus insuring their being driven equally together. The inner tube can be drawn to the surface at any time, either for the purpose of being sharpened, or of ascertaining the nature of tho soil, &c, and replaced with porfectease ; but in tubes of ¿Jin. or more iu diameter, provisioncan be made for ascertaining the nature of the valions strata the tube N passing through without removing the inner tube at all. Where the outer tube is found to beat a sufficient depth to insure a good supply of water, the inner tube is withdrawn. The valves, pump, bucket, and pear arc then placed in position—usually about liOft. from the surface of the water—the pump rod being made hollow, so that iu the event of grit or sand interfering with the proper working of the valves water can be passed down it on to them, and the obstruction cleared away—though this will be but seldom required, the pump being provided with a head valve, which always retains a column of water after it is discharged by the pump bucket. The whole of this arrangement will be clearly understood from the engraving, it being a very compact and serviceable job.

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These wells are well adapted for the colonies,

tropical climates, farms, gold and other mines,

also in testing for mineral ami other substances,

* e~hsed to advantage аз boring tools in

•artesian well making.

For mansions situate at any distance from the water the tube wells are found useful.

These pumps are now being constructed for the patentee, Mr. G. Watson, of l*laUtow,by Messrs. X. lilundell and Sons, of West India-road, Limehouse.

THE "PHANTOM" BICYCLE.
(For Illustration »ce page 277).

Tili; machine represented in the accompanying sketch has been the subject of no little controversy among some of our readers, and in placing this cut before thciu we would recommend those who may desire to have further particulars than we can afford space enough to convey to consult the pages of the interesting pamphlet, " The Bicycle ; or, the Wheel and the Way,"from which we make the following extracts:—

"The machine ¡a steered from the muidle of the frame, or

from both wheels, and not fiom the front wheel alone, as in •he ordinary bicycle, and as the front wheel only turns half as much as usual, it is never brought into proximity even with the rider's thighs. It is completely railed off too by the frame within which it is enclosed. In turning a corner, or on в curve, each of the wheels are put upon the same arc of a circle; the back wheel, therefore, always /vilotes the line of the leading wheel; it passes over cxactiy the sume ground, in fact; there is in consequence no 'drag.' lu the event of н fall the rider does not get hurt by the machine—that is, he cannot get * mixed up * or entangled in a painful way between the front wheel and the backbone, as in the ordinary bicycle. The shape of the framework ensures greater speed being obtained than does that of the ordinary pattern. There are very convenient * steps' for mounting and dismonnting, and the same contrivances are serviceable as safe and comfortable rests for the feet. Л spring concealed in the steering-socket destroys the vibratory concussions usually conveyed to the hands. Tbc cranks are readily adjustable to any length of throw, and when 'adjusted' they do not work loose. Both tlic wheels have fixed axles, and run iu gun-metal bearings provided with separate oil cups which do not leak. Lastly, the wheels are н grand improvement in themselves, being made upou the suspended principle in such a way that they act as springs, and assist in dispelling the concussions caused by rough road«. The general result is that a bicycle is produced which is of a decidedly improved appearance, which is much safer to ride, easier to steer, far less dangerous to full from, und whieh is much easier to mount and dismount. Finally, the tpeeJ, and consequently the ease of driving are improved by at least a tin ni."

The remarks us to india-rubber tires are of general interest —

"A rubber tire is usually- made up smaller than the rim of the wheel it is intended for, and is held in its place by being stretched into a groove, 1< riued iu the wheel by putting flanges ou each side of the rim. The defects of this plan are that when the wheel is pivoted upon its base, as when the machine is turning a corner, the rubber tire is wrung or twisted by the screwiug motion of the wheel upon the ground, and directly a part of it is raised a little above the edge of the flange, the whole of the tire instantly springs out of the groove. To get it back is a job of some difficulty, especially if the accident happens when ou a journey, us it takes at least two or three pairs of hands, and some little skill to stretch it in again. The stretchingon of the tire is intended to prevent it from being twisted out by making it impossible to stretch it further. This plan riot only frequently fwls to effect its object in Mi.it respect, however, but it exposes the tire to a constant dauger of, if possible, a worse kind in another way. Stretched rubber g$fu wherever it is cut, and as a very few

weeks' wear, especially ¡u districts where the roads are macadamised, produces a good many cuts in the tire, the result is that it is disfigured bv a number of ugly caps, and is drawn up into thick and thin places, instead of being of an evea thickness throughout its circumference. It then makes the machine bump und down, and becomes more of a nuisance than an advantage, and bv-and-bye the contractile tendency is strong enough in the thick parts to tear the tire completely asunder at one or other of the thin places.

"The rubber tire of the 'Phantom' isa different thing, however, and it is not liable to any of these disadvantages. The principle upou which the wheel is constructed 'dispenses altogether with the necessity for an iron tire to keep it together, as the rim is held in by the suspending rods; that leaves a wood surface upon which to fix the mbber tire. The latter is made half round, and has a canvas base made up with it in the vulcanising process. The canvas base serve« two purposes-, it prevents the tire from stretching in the direction of its length, and it forms a bed for holding the heads of short iron pins, which are driven through the rubber and into the м ood rim at intervals of about every inch nf the circumference. The heads of these pins are buried in the rubber, which closes over the hole made in driving them in, so thai they urc not seen or felt in anv way. They keep the rubber tire from being shoved off. then, as the rubber is not, nnd in fact cannot be, stretched in the direction of its length, it does not gape and stretch wherever it happens to get cut by sharp Btones. Consequently there is practically no end to the wear of the tire, as, in spite of the cuts it may have across it, it retains its uniformity of thickness and thereis never any defect in its action. Of course the cutting of fche rubber tire cauuot be prevented, but by this plan of fixing it on, the practical usefulness and luxurious effect is not diminished by the cutting, the gaping of the cuts being entirely prevented."

TO CLEAN PAINT.—There ь a very staple method to eleau paint that has become dirty, and if our housewives should ndopt it, it would «ave them a great deal of trouble. Provide a plate with some oí the best whiting: to be had, audhuve ready some clean warm water and a piece of flannel, which dip into the water and squeeze nearly dry; then take as much whiting as will adhere to it, apply it to the painted surface, when a little rubbing will instantly remove auy dirt or grease. After which, wush the part well with clean water, rubbing it dry with a soft chamois. Paint thus cleaned looks as well as wheu first laid on>, without any injury to the muta delicate colours. It is far better than uKlog soap, and doce uot require more 1 than ha.ll the time aud labour.

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LETTERS TO THE EDITOR.

[We do not hold ourselves responsible for the opinions of our correspondents. The Editor respectfully requests that all communications should be drawn up as briefly as possible.]

•»• All communications should be addressed to the Editor of the English Mechanic, 31, Татипоскstreet, CovenL Garden, W.C.

Al] «beques and Post Office Orders to be made payable to J. IDs Edwards.

ASTRONOMICAL, OPTICAL, AND GENERAL.

Sir,—Let me. 'uufrimis, congratulate my fellow subscribers upon the advent into your column* of our Great Solar i<pectioacopist, Mr. J . Norman Lockyer. Let us hope that after the appearance of so convincing a reply from the man, perhaps of all living the best qualified to speak ex cathedra on this special subject, we shall have no more vague guesses and expressions of doubt from people who are confessedly ignorant of the very elements of the problemwhtch they undertake to discuss.

Lower on the same page (256), I find two or three queries by Mr. H. W. Bishop, towhlch I will reply in order. First, tben.juat as twilight is fading, Is the most favourable time to examine the colour of a star. In the case of a star like Sirius, Mr. I ;. must remember that from its relative proximity to the horizon, atmospheric dispersion operates in tinging it very perceptibly P colour; and this is exaggerated by its projection o< the black background of the midnight sky. Of course, I am supposing the star to be one of a tolerably low magnitude. Some of the minute red stars require the darkest sky you can get, and some

Utile attention to boot, to discern their colour fairly. On the other hand, that lovely pair a Herculis is never seen to such advantage as In full twilight. I must confess my inability to " give the comparative brightness of the chief nebul« visible in a 3iu. achromatic," because I am unaware of any photometric process which is applicable to such a measurement: but if a rough eye estimation of relative visibility be of any use to your correspondent, I may tell him that of the nebula» now favourably situated for observation, hu ought to see 7ö Hersch. I. Virginie, and will have some difficulty with 99 Hersch. 1 Bobtis; while 418 Hersch. If. ßoötis,and 756 Hersch. IL Boolu will be beyond his power altogether. 13 Messier Herculis he will eitherbarelyresolve,or see asa bright nebula, according to the excellence of hie instrument. 57 Ma j.,. r, the Ring Nebula in Lyra, will. In a firstrate Instrument, show traces of luminosity inside of the ring proper. This is all vague enough, but I do not see well how to frame my response differently. Before dlemsaing' this branch of my subject, I may say

NÏW STYLE Or' RAILWAY.

that June is, as my querist probably knows, the worst month of all the twelve for the examination of neUulse.

I may tell " Investigator" (also on p. '¿56) that the method now universally employed, where practicable, for the determination of longitude, is that by the Electric Telegraph. As he appears to possess '* Loumis's Practical Astronomy/' I can refer him to pp. 3>£, et sq., of that work for full details of the method adopted in practice. It may, however, serve to show with what extraordinary accuracy longitude can be obtained by the transport of chronometers, If I mention that of Mr. Airy, in Ш4, superintended the transmission of thirty pockrt chronometers ten times backwards and forward between Greenwich and Feagh Malu,at Valencia, In the extreme West of Ireland ; and that when the difference of longitude between these two places was redetermined galvauically in the summer of 1863, the result was almost precisely identical with

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THE "PHANTOM" BICÏCLE.—(Described on page 276.)

that obtained by the older method. Moon Culminating Stars, unless observations be very much multiplied and great care be taken toobser ve both limbs of the moon, give but indifferent results, and Luuardistancc», even in the hands of skilled observers, are only pretty good; but Occultationsjof Fixed Stars;by the 'Sinon when carefully observed, and rigidly reduced, are very much better still. Secondly,every visible Occultation isobserved at Greenwich, as are the phenomena of Jupiter's Satellites &e. These are published at intervals lu the "Monthly Notices of the Royal Astronomical Society"; and this answers your correspondent's third query as well. ¿Next, all the observations at Greenwich of the Moon, both with the transit circle on the Meridian, and with the altazimuth off it, are "for the purpose of detecting errors of the lunar tables." The Greenwich observations are published by John Murray, of Albemarlestreet, London. With regard to the immediately following question, he may take the length of the Polar semi-axis of the Earth at 208537<38ft., and that of the equatorial semi-axis he may deduce from It by con

ceiving with the Astronomer Royal that the clliI, amounts to 003352. I must, however, add that a most elaborate series of investigations, undertaken by Colonel Clarke, of the Engineers, tends to show that the ellipsoid which best represents existing measurements has its major axis (Equatorial) In Longitude 13° 5b' 5* E, and that the greatest and least

1

values of the meridian compression are in lon

286-779

1

gitudo 13° 68' 5* E., and In longitude 103°58' У К

309 86t

The difference of the Equatorial semi-axes is 5308ft. or, roughly, about a mile. It will hence be seen that the figure of the Earth Is by no means absolutely symmetrical, nor even tliatofauy solid of revolution. Finally, " Investigator's " refercnces to page 130, Лео are presumably te those of some volumof the "Nautical Al inanac," but, in the absence of the name of the work to which they pertain, they are just a little vague.

"The Welsh Shepherd," p. 256, like numberless other

people, severely exercises himself about a question upon which as much nonsense, physical and metaphysical, has been talked. as has been uttered» about most things. The whole matter seems to He in a nutshell. If, from the way our eyes are placed In the head, we have to raise them to look at a part of an object, we say that that is the top ; if we have to depress them to see another part, we call that the bottom. Our whole notion of iv and down ie derivad from motion ; and if the im age fell upon the stomach instead of the retina, and we had to raise our body to perceive it, we should say that that part was the highest; If, on the other hand, the body had to be lowered, wc should call the part of the image which necessitated such lowerlug for its perception the lowest. Ihr socalled " inverted image ■ on the retina, is treated by most people as though, so to speak, we saw tku; albeit to do so, we should have to have another eye behind it!

What, In the name of fortune; does "F. W. M."(p. 257), Imagine t Is adding to a controversy which has been carried on usque ad nauseam, by reiterating what has been said over and over and over again about the Earth and Moon forming parts of one solid globe r

Fellow of The Royal Astronomical Society.

NEW STYLE OF RAILWAY. Sir,—I send you a drawing of a new style of raceway just introduced into Lisbon. It runs on one rait along the common thoroughfare. Il the Illustration you see that the engine aud carriage* have small wheels, which run on the rail, and large one* on the road. The cylinders are under the boiler, just like any other engine. The wheel which the mau tu fr^uc

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