THE ENGLISH MECHANIC AND WORLD OF SCIENCE. TO OUR SUBSCRIBERS. AT T the commencement of a new volume it may not be out of place to make a few remarks about the ENGLISH MECHANIC and its prospects. Since the commencement of our last volume we have absorbed three weekly scientific publications: probably such a thing never occurred before. The Mechanic, a widely circulated penny paper, was absorbed on the 25th of March last. Soon after thing more commonly overlooked by amateurs than that the easiest way to do a thing is to do it properly and thoroughly. Every one who means to make even the simplest electrical instrument will find the advantage of making a winding in post. As a rule these cards will not supersede | be a loss, for nothing is more certain and yet no- AND APPLICATION. followed Scientific Opinion, a high-class scientific ELECTRICITY-ITS THEORY, SOURCES, already wide circulation, and at the same time multiplied our correspondence. We can therefore say without egotism that the ENGLISH MECHANIC may be regarded as something unique in British journalism. It not only, as we have frequently said, enjoys a wider circulation than all our other scientific papers put together, but it has a larger number of efficient correspondents than all of them united. This fact is worth recording, as it is unquestionably the main cause of our great popularity and, we hope, corresponding usefulness. We have heard recently a great deal about cooperation and the extensive and permanent advantages it is likely to confer on the community. The ENGLISH MECHANIC is a monument of co-operative industry. We have at least a thousand correspondents who send us, in a condensed form, the fruit of their reading or the result of their experience on the thousand-and-one questions which interest students, artisans, manufacturers, and scientific inquirers. There is hardly a question relating to the application of science and art to industry, or the modus operandi of scientific investigation, which may not be asked and answered through the ENGLISH MECHANIC. Besides our original and selected articles, our extensive and varied correspondence, at least twelve dozen, questions, either in the form of letters or queries, are asked weekly through our columns, and about nineteen out of twenty of these questions get answered. It would, in fact, be impossible to say the amount of individual and national benefit the community derives through our columns from this new method of mutual help. As an organ for the distribution of knowledge appertaining to the everyday wants and inquiries of scores of thousands of people the ENGLISH MECHANIC stands without a rival. In all probability this means of mutual enlightenment through the post and our pages, great as it now is, will be materially increased by the new postal regulations which will commence on the 1st of October next. Then a question or an answer may be written on a stamped card, which will be supplied by the Government at one halfpenny each, and sent to our office through the 165. By J. T. SPRAGUE.* (Continued from page 580, Vol. XI.) It will MANY amateurs wish to possess instru- 166. Fig. 46 shows the construction. A is a 66 Sigma." PLAN strument from the first, and it is very easy to make so as to suit many purposes. In a piece of wood, say 6in. by 18in., mortice at one end an upright of the same width, and 6in. high: mortice a similar piece into a short foot, so that it can be fixed by screws at any part of the length of the base; on the top of each of the two uprights hinge a piece of hard wood, and provide it with a several holes of various sizes, which will form hook to hold it down, and then at the joint bore bearings for any required mandrels, which are inserted by unhooking these top pieces; such a stand will suit for the present instrument, for winding coils, electro-magnets, &c., and for transferring wire from loose rolls on to the reels, on which it is most convenient to keep it. 167. The first thing towards the instrument itself is a strip of copper plate about 5in. wide, formed into a sheath B round the bar A; from its upper face, under E in the figure, is removed a strip a quarter of an inch wide, and in the middle of the lower face a hole is bored, and fitted with a piece of brass tube of in. bore, soldered firmly at true right angles, and into this the wire b is inserted. C, D, E, are of fin. wood, C and D cemented firmly to the copper (the brass tube going through C), but E is intended to be removed when the instrument is completed. F F are of three quarters wood, 44in. long and 2in. wide, with mortices cut in them exactly parallel with and 1fin. distant from the bottom edge. These are also cemented to the copper sheath, the projecting ends of which are then turned back upon the wood (part of F is cut away to clear the view). A frame is thus formed, leaving two spaces for the wire about in. wide, in which while drying pieces of wood should be inserted. The space to be thus left depends upon the wire used, but the distance between the inner faces of FF should not exceed 2in., and should just contain the wires firmly, so as to keep them truly parallel and close. In my own case No. 16 silkcovered just takes 10 turns, that is ten one side and eleven the other, a difference due of course to the way the wire lays on. A strip of card is now glued across D D on each side, leaving E free, and then a lining made throughout of silk dipped in melted paraffine. The saw cut through F2, at d is provided for passing the wire through, for connections. The beginning of the wire (which call end 1) is passed through this, and it is then wound tightly on; as each layer is completed melted paraffine is rubbed on and soaked into the wire covering, and a strip of the silk prepared with paraffine wound over it to prevent any accidental contact. This precaution is always desirable when silk-covered wire of large sizes is used, as the covering is very liable to injury. It is also an improvement in all electrical instruments to pass the wire, either beforehand or while laying, through melted paraffine, or what is much better, a mixture of eight parts paraffine, one part beeswax, and one part boiled oil; paper, silk, &c., passed through this, may be laid aside for use as required, and remains perfectly flexible and sound, which is not the case with paraffine, either alone or mixed with wax. The wire may be wound to several layers in one partition first, and then carried to the other through the gap left for the purpose in one end of the middle division. Ten complete layers may be thus laid, and then the wire is doubled and passed through the saw cut d in F2, and a wire soldered to the bight thus passed out will be a connection, to be called 2. The return wire now makes two further layers, when another bight-3-is passed out, and one layer more completes the wires, the end 4 being left free for the present, and two or three turns of prepared silk or paper is placed over all to protect the wires. that the instrument works on the central pivot as formerly stated, and by doing this in the manner shown (Fig. 44, p. 580), the instrument becomes a sine galvanometer, and all its indications are rendered comparable and of fixed values. 168. In delicate instruments it is usual to suspend the needle by a fibre of unspun silk, or by a hair, though this last I have found presents a considerable resistance to torsion. This plan is troublesome on several accounts, and the plan I am now to describe answers perfectly well. All that is needed if the needle hesitates to move, is to give the lightest tap on the stand or table. The brass tube in the middle of the coil (which must not project in the least within the cavity) may be plugged with a slip of cane or soft wood, and a wire inserted in this so that its point rises exactly in the centre of the copper plate, and about gin. above it. A long fine needle is the best thing possible for this, but a still better plan is to drill a hole in a piece of brass fitting the tube, and to insert the needle in this; it can then be exactly adjusted as to height from below the instrument. This brings us to the final element, the magnetic needle. It is built upon two pieces of the very thinnest tubing, one sliding firmly within the other. Fig 47, a, is a section of these E being withdrawn, the upper surfaces of F F and D are now to be very carefully brought down to the level of the wires, or if the wires have risen slightly over them, they must be raised with thin wood or paper, to obtain a smooth surface, perfectly parallel with the lower faces and with the middle space. This being done, a piece of stout sheet copper large enough to cover the whole, with a hole in it corresponding with E-that is, 2in. by in. is placed upon the surface and cemented to it. The terminal wire 4 is now soldered to the middle of the end of this plate, to which it approaches from the lower side of the coil, a prolongation of it being left which we will still call 4, while to the opposite end of the plate is soldered a stout copper wire which we will call 5, and which will be the point through which the current enters. We have thus four circuits under command:-1, the single passage through the copper plate, which thus serves the double purpose of checking the needle in its swings and acting as a single turn of wire; 2, this extended to one layer of wire; 3, with three layers; 4, the whole coil. The next thing is the stand, a piece of wood 6in. or 8in. square, or round, fitted with levelling screws. In the middle of this a hole is bored, in which the lower extension of the wire b is placed, and then F F are glued to the stand or fixed to it with brass screws, for of course no particle of iron must be used about a galvanometer; b is withdrawn and A removed; the various terminal wires are then taken through holes in the stand to binding screws, No. 5 to one on one side, the others to four in due order on the other side, and a frame with a glass top is then placed over the coils. It is, however, best to make the stand so needle for use by itself, and another couple exactly like that shown, but with a non-magnetic indicator in place of the upper needle; in fact it is by thus employing needles of different capacity that the instrument becomes capable of such a great range of utility. 169. All that now remains is the adjustment; a line drawn on the copper along the middle of the opening in the face, ought to give the true zero line, but it may not be exact. Mark it, however, and another at exact right angles, the vertical point or needle occupying the intersection of these lines, and fix upon the face a paper with lines on it corresponding with these, and with a circle of the diameter corresponding to the needle graduated to degrees; place the single needle on the point and adjust the instrument exactly, taking care to have no iron in the vicinity; connect a perfectly constant cell, such as a Daniel, in good order, to the first pair of ends, and note the deflection, using any resistance if needed to bring the needle to some exact mark, say 30°, then reverse the connections and see if it deflects to the other side to exactly the same; this will depend partly upon the direction in which the connecting wires have been led, whether they have been brought up truly vertical in the middle line and soldered in the middle line of the plate; next bring the outer layer of wires in the circuit, and repeat the trial. If both deflections are alike, the zero line is right; but if not, the graduated circle must be moved round just half the difference, the instrument moved to correspond, and the experiment repeated. tubes, showing details of full size. The upper part is the largest. In the top of it is the bearing on which the whole is suspended. This is best made of agate, which can be obtained ready formed for the purpose; but it may be of brass drilled into a cone. These bearings are also easily made from a piece of thickish sheet brass, by means of two steel punches, one with a fine point, the other slightly rounded, and a lump of copper for a matrix. The brass having been annealed by heating, is raised lightly with the second punch, and then finished with the sharp one; annealing several times during the process, to avoid breaking through; a ring, such as a section of the smaller tube, is inserted in the tube, then the bearing, which is fixed either by a touch of solder or by burnishing the edge of the tube over it. The lower tube is now adjusted to the exact length, and upon it is fixed the lower needle which is to work in the internal cavity of the coils. This is composed of two pieces of watch-spring 2in. long, touched lightly with solder at the middle, compressed together and soldered to the tube. For such light soldering as this, the best plan is to fix a stout copper wire 3in. or 4in. long in a piece of wood, tin its end, and hold it in a gas flame so that this end projects; and against it touch the work. Before fixing finally, this needle should be magnetized and tested as to its balance upon a fixed vertical needle, as the whole system must hang so that it shall be true, and touch neither the walls of the cavity nor the supporting point, and this is only to be secured by making each separate portion true. The upper needle is also formed of watch-spring, bent as shown, and then hardened again. This brings the weight below the centre of motion, and the slight curvature brings the points close down to the surface on which it indicates, and covering a circle of 34in. diameter. This needle is soldered in the same way to its tube, and made to hang perfectly true when magnetized both endways and sideways. This needle is now fitted for use as a single needle, or as an astatic system, in which latter case the poles are turned, as shown, in opposite directions. The dimensions given leave the upper needle the most power, owing to its length, to a degree sufficient to bring it speedily back to the N. and S. line. If greater delicacy is required, an upper needle of force only just beyond that of the lower one must be used; but though I give this plan, I recommend as much better the providing separate systems, making the complete astatic system fixed at the joint when adjusted (because it is very difficult to ensure accuracy each time of changing), and also an upper The instrument thus adjusted, the needles are tested similarly; they are put together as nearly in one line as may be, and tested as before by reversing currents (the paper being now cut away in the middle to permit the lower needle to enter); they are then shifted until the deflection is the same both ways, when the full force of the instrument should place the upper needle either way, exactly on the line of 90°; the joint is then fixed, or a fine line marked on the tubes. Of course this instrument is nothing strikingly new; the principles are the same as those of the galvanometers made usually, and the differences are all a series of details; but they are details arrived at by an immense amount of experiment directed solely to the end of making a very compact instrument of great scope. The dimensions, wires, &c., given are of course capable of any amount of variation, and more or less in number of branch connections may be used, and for use with circuits of very great resistance a second would be needed, made with fine wire of great length, which would be better than adding to the depth of this instruby coiling fine wire on at first, though a greater length of No. 18 or 20 might with advantage be used in place of the first ten layers of No. 16, where the greater resistance thus caused is not of consequence. 170. In closing the subject of galvanometers, a little instrument I have devised for magnetizing needles may be useful. It is simply a coil 3in. long, of silk-covered wire, No. 18, wound on an oval cardboard core, and the numbers of layers increasing to the middle; it is divided into two, and fitted with tubes on each part to slide over brass rods, and the wire is formed in the middle of a flexible metal cord to allow the two parts to slide apart; this allows double needles, like those just described, to be magnetized, by slipping each in turn into the coil, and passing a current from a bichromate or other powerful cell; a few seconds are sufficient, and with this apparatus it is no trouble to magnetize needles at any moment Having ascertained which end of the wire gives N. polarity to that end of the needle, it should be marked as shown, and always so connected; there will then be no confusion as to the direc tion in which the needles are being magnetized, and this is important, as the south end requires to be the heaviest before it is magnetized in order to balance afterwards. (To be continued.) A PRACTICAL TREATISE ON THE HARMONIUM.* BY HERMANN SMITH. (Continued from page 556, Vol. XI.) THIRD DIVISION.-CHAPTER VII. give them a bolder tone, and a similar error is very prevalent respecting organs, that pipes of extreme or large scale secure powerful tone. The truth is that size is not necessarily a guarantee of strength, on the contrary it is often a source of weakness. Proportion rules all, proportion not alone of dimensions of pipe or channel, but of the relation of all details having any influence or share in producing results. OF THE CONFIGURATION OF WAVES IN CHANNELS speak at all, except at strong pressure, on a AND CAVITIES. "The invisible and creeping wind."-Shakespeare. FAVOURITE epithet is this with him who A has for ever associated the stream of Avon in the reverse instance, the stout reed on a shallow of waves upon each other, occasioned by the with his own great fame. Jessica, it will be remembered, says:— "Here will we sit and let the sounds of music And the poet repeats again, in the "Tempest," his intuition of the sinuous motion of the sound waves, "The music crept upon me by the waters." These expressions of Shakespeare rose into memory, as we leant upon the bridge that spans the lake, watching and questioning, as is our wont, the many-figured undulations of the waves. Gathering in our view the lake, with its green island of shelter, the drooping willows and grey alders shimmering in the breeze, the belt of rich foliage shutting out the busy world, the old abbey towers in the background showing their pinnacles above the sky-line of the leaves, and the tall spire hard by golden in the setting sun, soft shadows filling the undergrowth of the wild-fowls' covert, the white swans whiter for the tender gloom, and the cool waters lightly ruffled by the myriadfooted "creeping wind," what wonder if these lines of Shakespeare should come deftly to the lips, or that phantasy out of this scene should have wrought for herself a replica of that quiet picture so familiar to the world, the old church spire rising above the trees, the larches and alders and nodding sedges of "Avon's softly flowing stream !" Goethe observes, and wisely, that "place ourselves how we will we always conceive ourselves to be seeing;" and so it always seems to us that the vision that accompanies thought becomes between ourselves and our readers the best interpreter of the thoughts that are seeking intelligible utterance and faithful expression. Here, as we sit and write, that scene revives in intimate connection and affinity with the problems we pondered on. The association of ideas is in itself a kind of picture-teaching; it is nature's way of dramatizing the lessons she would have us remember. If the thought is suitably toned, by fixing the scene we may hope to fix the thought permanently. As the swan comes up the lake, sailing in placid dignity, how broad a furrow her white bosom cleaves! as she advances, the waters part, and the waves as they rise deploy on either side in long lanes of light, hurrying in fanlike array to dash themselves upon the resisting banks of the lake. Onward the beautiful creature comes with moon-white plumage raised, approaching the bridge she slackens speed, lowers her sails, and serenely floats at ease beneath our gaze. When she moves she ploughs the deep water. Her dusky cygnets around her paddle and splash, and make a host of little surface-waves, which die almost as soon as made, absorbed into the larger mass When the stately swan moves you can see the swell in the depths below, and trace its influence in far-spreading undulations. It is only swans that can so stir and give motion to the deep water: cygnets agitate only shallower circles. The waves which are deployed in the track of the swan accumulate power from the support of the underswell, and spread with energy to great distances until checked in their career by opposing banks. Let us go to the margin and see how they behave themselves, not forgetting by the way one lesson we would impress, that it is of little use having deep channels in our sound-boards unless we have swans to stir the depths. of water. There are few things more difficult to convince amateurs of than this, they hold tenaciously to the notion that increased depth of channel will The copyright of this treatise is reserved by the author. become flatter in pitch. Cone-shape allows most freedom to the stroke of the reed. The reed is its own ruler only when it is left to itself. Whatever its natural pitch, every pipe channel or cavity with which it is associated will lower that pitch. The degree of flattening dependent primarily on the configuration of such channels simple or complex, and subsequently on the nature of orifice, pallet, and other adjuncts. In organ pipes, and Reeds giving the note of the pitch CC C 16ft., in all musical instruments of the wind species, we may be from one to four inches long, or of any know that the most marked distinction exists in diversity of lengths between these, and yet they the quality of tone elicited from those which would not each be equally effective on the same have cylindrical and those which have a conical channel. A light reed would probably scarcely bore. An open pipe if conical is sharper in pitch, a stopped pipe if conical is flatter in pitch, as channel that gave powerful resonance to a stouter compared with pipes of parallel sides. The curved reed, it would be ineffective to stir the depth with shape, again, must exercise some peculiarity of inthe requisite fullness and uniformity of sway; and fluence through the varied modes of impingement channel would yield a harsh or rattling tone. So amount of difference between the inner and outer it is as regards the compass of the scale from circles of convergence and divergence. In the bass to treble: the treble reeds will not speak at official report on the Suez Canal, there occurs a all if the channels are too deep, for, unable to remark which has great significance for us, showattain an amplitude of vibration sufficient to act ing the incidence of undulatory action-" Another uniformly upon the mass of air, they are checked wall is much needed on the east side (like that at the initiatory impulse; like ill-trained horses on the west) where the curve already shows the the reed and channel do not pull together, some usual signs of scouring out on the outer, and dediscrepancy in the timeing of efforts renders the positing on the inner side." What the phenointended assistance nugatory. When reed and mena teaches you can, we should hope, upon this channel are assorted in true affinity not only is hint develop for yourselves-it is but a stray there a difference in quality of tone but the union fragment, yet it would form a text for many a is characterized by an alacrity of articulation, the discourse on acoustics, or for a disquisition on the moment they are called upon to speak at a touch organ of hearing, and notably upon the cochlea, they yield, the tone is started smoothly and sus- that doubtfully understood little structure, a tained equably, and if the reed is of pliant nature marvel within a mystery. The earnest thinker the crescendo and diminuendo will be of admir-will find food for reflection in everything that able gradation. The depth of channel is, there- comes under his observation; earth, air, and sea fore, valuable only as it is proportioned to the are ever ready to do him service, and illustrate strength and active display of the reed conjoined his most cherished thoughts. to it. In passing we may likewise remark that the commonly accepted opinion that broad reeds must be loudest in tone is equally wrong, they require a stronger flush of wind to elicit their power, and, all other things being equal, a narrower reed would develop a greater strength of tone. Strength resides in length,-power is determined by range. Many of you have no doubt seen those unique examples of Chinese ingenuity, white ivory globes, curiously carved and perforated, and strangely wrought one within the other, in graduated series. Whilst we have been contemplating undulating waters and waving cornfields there is one thing we should not remain unconscious of that we have had under view only a profile of wave Resuming our observation of the waves, we motion; that interior and subtle motion, the notice that the abutment of the bridge runs down vibration of air, creeps forth uniformly on all sides, perpendicularly, and the embankment presents its impulses insinuate themselves to the fullest itself at right angles to the level of the water. bounds their energy will carry them; the waves Watch the sinuous line of waves whilst the swan of sound will penetrate every outlet, pass through is returning to her island rest. As the waves minutest cracks and fissures, and then disperse strike on the face of the stone embankment they themselves again like light above and around, for, break in perfect semi-circles, one within the other, as Peschel states, In an equal resisting medium an interlinked lace-work pattern, so even and re- all vibration would be in spheres." These gular-they represent the half-wave. In the end of a hollow ivory balls we introduce for similitude to stopped organ-pipe a similar half-wave is formed. If vivify the conception of the wave-spheres of air. now we look further along and find the smooth The water exhibits to us rings of ridge and furrow stonework shelving or slanting downward we may-circles of elevation and depression; the air note that from the same roll of waves, not uniform would propagate its undulations in all directions semi-circles, but segments of circles or forms at once around the point of vibration-would more or less oblate are obtained, and beyond this present zones of condensations and rarefactionsshelving station, and where the margin changes spheres around spheres-density and rarity alterto rough, rugged, agglomerated stones, the pattern nating, as in rude illustration these ivory spheres made by the breaking waves becomes irregular, a encircle each other with intervening spaces, reprevariety of confused forms, contentiously aiming to senting rarer matter between the denser. The inobliterate each other. Whatever shape is given finitesimal sphere-motion within the channelto the embankment or shore for the waves to imagine how it must be influenced by the conbreak upon, we shall find correspondingly a differ- tour that limits its capacity for expansion, ence in the behaviour of the waves. Every form uniform expansion, each variation of enlargement, is the expression of a definite force, every differ- contraction, or curvature of the channel or cavity ence of form betrays the difference in the compo- causing different impingement of waves, different sition of forces direct and reflected. You can there- relations of involution, introversion, and aggrefore imagine the process going on in these sound-gation, and then remember that out of this coming cavities, and estimate how differently the waves plexity of form there comes forth the blended of sound must be affected by the shapes of chan- effluence of tone which we call quality. nels; the channel perfectly parallel on all sides, would bear analogy to the right-angled embankment, the half-waves we may consider to be as complete in the interior mould of the channel as to the eye is the enchaining of the semi-annular pattern fringing the borders of the lake; and in similar relation of cause and effect the sloping sides of channels would produce different introversions of the sound-waves. If three reeds are taken exactly alike in pitch, and in their scale each the counterpart of the other, if these are placed on three different channels, each of different shape but as nearly as may be similar in capacity, what will be the result on sounding them? Three notes in unison. No; the shape of channel will have exercised its influence on the pitch of each, and coincidently have given a varied flush of colour to the quality. The reed upon the channel whose shape spreads in the direction of the pallet aperture, will have risen in pitch as compared with the reed upon the channel having parallel surfaces, whilst the reed upon the channel which contracts towards the orifice will have We account for the individualism of tones by the modifications given to the forms of waves by the surrounding walls of the cavities in which the tones are produced. The qualitative resonance is an accretive compound of harmonics upon the fundamental note, or, in other words, it is literally a growth of form upon form, these forms being clustering, successive, and transitory, as soap-bubbles blown in clusters. It is generally admitted that " quality" is due to the mixture of harmonics, and to the comparative strength and the diversity of the grouping of these overtones. We have drawn your attention first to the lineal undulations breaking up into divisional parts and inducing the manifestation of harmonic tone, and then to that equally or more important kind of form arising through the impulsions and counterimpulsions breaking in upon these from the walls, and according to their configuration still further modifying the relations of the harmonics. The lineal and the inflected impulse bear analogy to the peculiar coexistent condition of a vibrating violin string, its periodicity or constancy of pitch, and its diversity of quality-giving power, according to the individuality of the performer. Dr. Young has exemplified this in a remarkable manner. He examined the string of a violin when vibrating, and by throwing a beam of light upon it, and marking the motion of the bright spot which it made, he found it to describe various and complicated curves according to the different manner of drawing the bow, and he gives the following graphical examples to show how much the vibration produced by one player may differ from another, although the pitch of the note given is in each instance precisely the same. In the violin and other solo instruments the player commands the quality by his personal skill in intonation; in the harmonium, on the contrary, the player determines very little, there is an abiding quality given by the configuration of the channels. The apertures and pallets are comprised under the configuration, for they are indispensable to its completeness, and we shall see how important is the part they bear in the quality of the re sonance. WE (To be continued.) THE MICROSCOPE.-HOW TO CHOOSE AND HOW TO USE IT. (Continued from page 579, Vol. XI.) E have not spoken of binocular microscopes as yet. Chiefly because the price of a good one would prevent many of our readers from purchasing, and also because those who wish for information respecting them can easily obtain it from the price list of our makers. We will therefore content ourselves with expressing our satisfaction that a good binocular with two powers may now be purchased for £10, and with mentioning that such an instrument (provided it can readily be used as a monocular) has many great advantages and should where possible be purchased. If any reader require special information respecting this instrument we shall be happy to afford it through the usual medium. to the object; removing his finger the water rushes "You have omitted the live box," says one. The covers must be fastened to the slides. For thousands of miners; interesting from its remarkable and unique fossil and lithological characteristics; it is at once the chief and most useful of the kingdoms of the rocks. In the strata of the Old Red Sandstone we found traces of the former existence of vast seas, peopled with fishes and molluscs, radiates and crustaceans, whose remains are now buried deep in the deposits of their ocean home; but in the shales and limestones of the carboniferous beds, we come upon the relics of a rank vegetation, extended over large tracts of country, and which must have vied in luxuriance and fertility with the present forest lands of Brazil, mingled with a profusion of marine and semi-marine organisms, whose corpses seem as if turned to stone by some Medusa of their day. This system is divided into three groups or series, called the lower coal-measures, or carboni. ferous slates, the mountain limestone, and the upper coal-measures. These three groups succeed each other in the order above stated, but it is by no means uncommon to find one or even two of the three absent. All that is affirmed of their order of succession is, that they are never found in a reversed order; thus the mountain limestone never appears either above the upper, or below the lower coal-measures. Adhering to my former method I shall first proceed to the consideration of the lower coal-measures or carboniferous slates. This series embraces a great variety of strats, from shales of a dark colour, slaty grits, limestones, and thin seams of coal, to thick beds of white sandstone, coaly shales, veins of ironstone, and shelly and clayey limestones. There seems to be no doubt that this portion of the Carboniferous system was deposited on the beds of rivers and estuaries, as its fossils are de cidedly fluvial; freshwater shells, and reeds akin to those now found on the banks and deltas of our rivers, and lizard-like fish of a species somewhat analogous to the cayman or alligator of the present period, are its chief remains. The strats are for the most part laminated, and show no ripple mark or other sign of marine formation, but exhibit distinct traces of deposition in estuaries and tranquil streams whose waters were loaded first with one substance then with another; at one time covered with plants torn from its banks by the influence of some inundation akin to those which periodically take place on the Nile, and depositing them on its bed; at another burying them beneath thin bands of varying clay and silt; here dropping, in narrow strips of ironstone, the iron with which its waters were abundantly charged; there spreading the shells of defunct organisms in beds of several feet in thickness. The vegetation on the banks of these rivers must have been most exuberant, far surpassing any of the flora of our epoch, and its general diffusion over the whole extent of the globe points out that one uniform climate still prevailed. Club-mosses and arborescent ferns mingled their beauteous foliage with the huge yet graceful forms of Araucaria-like pines with an equal profusion in the torrid and the frigid zones, and a mild and genial temperature appears to have existed throughout the world. Proceeding onwards, we next come to the mountain limestone group, a formation consisting of variegated marbles of a sub-crystalline character, bands of oxide of iron, and lead, zinc, and copper ores. generally occurs either in the form of thick beds of limestone or of thin strata of calcareous rock, divided by alternating beds of shale, chert nodules, and sandstone. Its stratification is very marked and distinct, though generally greatly rent and dislocated by the irruptions of trappean rocks, with which it is often found associated; on this account its scenery is of a very grand and striking nature, which is still further enhanced by the caverns and fissures by which it is intersected. These caves are formed by the action of streams of water, which flowing through the chinks and fissures caused by some igneous convulsion, AND gradually wear away the rock and form hollows of, in some cases, great extent and most exquisite beauty. Water percolating as above through the calcareous strata becomes charged with lime, which it deposits in the form of stalactites on the roof and sides of the cave, like natural columns and pendants of the most airy and graceful aspect. H. P. We may divide the minor accessories of the microscope into two sections. Those used in preparing objects for observation, and those required by the mounter. Commonly the preliminary preparation of the object has to be done, if it be minute, under a magnifying power; The student may now provide himself with a several forms of microscopes, called dissecting bottle or two of cement, glass slips and covers microscopes, are sold for this purpose, amongst (papers, too, if he like), a bottle of Canada balsam, which Collins', Lawson's, Baker's, and Quekett's, of glycerine (Price's), of turpentine, chloroform, are the best. The author, however, has always and benzole. Having provided himself with these contented himself with a simple pocket lens, he may, if he will, accompany the author through costing eighteenpence, which he fixes on a small a week's mounting campaign, and then through a stand, and finds to answer every purpose as well week's work at vegetable histology, with a touch as, or nearly so, the most expensive instrument. at that of animals, and, finally, wind up with a day For the dissection of animals and insects the in the country. Whether this be all accomplished student will need a glass dish, a small piece of time will prove. leaded cork and a few pins; a number of needles fixed into camel's-hair pencil-holders, some of these needles being bent at different angles and THE WORLD: ITS FORMATION being of various degrees of fineness. These are most useful in dissecting or teasing out small details of structure, and no histologist can dispense with them. Besides needles a fine pair of scissors and a couple of, or three, scalpels made specially for this work, and to be purchased of any instrument maker. These are all that will be required at the outset in the way of cutlery. A few fine glass tubes of a few inches in length, ground smooth at the end, will also be of use, especially to the animalcule student. The use of these, called dipping tubes, is simple. The worker places his finger upon the upper end and lowers his tube until it comes into close proximity ANTIQUITY. BY ARTHUR UNDERHILL. ASSING upwards in our tour through the PASS confines of that most important and interesting It I am, while writing this chapter, staying at a little town in the south of Devon, near which & mass of mountain limestone is thrust up in a huge bold mass. A chasm divides this into two portions, and at the bottom runs a streamlet bounding over the huge boulders of calcareous rock, which have from time to time fallen from the に precipitous cliffs above. On either side of fossils of this portion of the system are eminently marine, consisting of corals, shells, and encrinites in great abundance, so much so that it has often been called encrinal limestone. Sauroid fishes, too (saurus, a lizard), are sometimes met with-huge creatures, the terror of their smaller neighbours; coal plants, mosses, and ferns also occur, principally in the shales (see Fig. 2), radiata and bivalves, fishes of several FIG. 2 very abundant. The group is however chiefly ing by machinery have before been made, but none with perfect success. The most noticeable was Jordan's, used, or attempted to be used, for some of the wood-carving in the Houses of Parliament. The great cost of his machine, together with its great size and weight, rendered it altogether beyond the means of the ordinary carver or amateur. Messrs. Cunningham & Dabb's machine, on the contrary, only weighs from cwt. to 3 cwt., according to its size. It can be worked either by steam power or a fly-wheel; requires no skilled labour, and performs the work with an exactness and speed not to be approached by hand-carving. Half an hour's practice will enable any one to work it, and it is so constructed as to render the merest novice incapable of spoiling his work. We saw at the works in Cadby's buildings, Leather-lane, Holborn, a portraitmodel of Charles Dickens, and another of the venerable countenance of Mr. Cunninghamprobably familiar to many of our readers--both executed in oak with the expense of less than a tithe of the time and cost hand labour would involve. The machine is also available to a great degree for block letter cutting, turning out over sixty well-cut block letters an hour. The carving machine, at work at the time of our visit, has been sold for the oak carvings now being executed in the restoration of Bath Abbey. The working of the machine, as we have said, is very simple; the work is placed under the cutting tool (shown side by side with the tracer), and the latter is moved at will over the outline of the model. The Carboniferous system is greatly invaded Each moving at the same speed and in the same by trappean irruptions, which threw up the moundirections as the other, a perfect copy is obtained. tain limestone into the picturesque hills in The cutting tool of course revolves by means of which it occurs, producing faults and slips the band attached to the fly-wheel and the nein the coal-measures, which are of the greatestcessary suspension is obtained by means of the inconvenience to the miner. A great variety of adjusting spring shown. metals are obtained from this system, which is, in fact, the chief repository of these valuable substances. So prolific is it indeed, that it has been termed the metalliferous system. The scenery of the group is very tame, being flat and uninteresting, except where the mountain limestone is found, when it is of the most picturesque nature, displaying cliffs and precipices of tremendous depth and irregular outline. Sometimes, however, the coal-measures display considerable beauty, as at Dudley in Staffordshire, where they are thrust up by basaltic rocks into a very pic-weights and the molecular formula were conturesque and rugged hill. On the whole, how "Primeval forests wrapped thee round ever, it is interesting, chiefly from its mineral, rather than its scenic characteristics. (To be continued.) AN INTRODUCTION TO INORGANIC BY GEORGE E. DAVIS, Honours Certificated Science Teacher. (Continued from page 555, Vol. XI.) CHAPTER III. our last chapter we saw how the atomic trolled by the law of isomorphism; in the present one we will notice other laws which bear upon the subject, viz., Dulong and Petit's law of Atomic heats and Gay-Lussac's law of volumes. We will commence with this latter. After the discovery that acids combined with bases in a Dalton constructed his atomic theory, a more definite proportion and vice versa, from which fact simple relation in the combination of gaseous bodies was discovered by Gay-Lussac. In his memoir "On the Combination of Gaseous Sub stances with one another," he clearly proved that combination takes place in definite parts by volume; according to his experiments 100 volumes of oxygen united with 205 of hydrogen, but the error was rectified in 1805, when he showed, together with Humboldt, that 100 volumes of oxygen exactly required 200 of hydrogen. But this was not the whole observation, there was a condensation on combination; two volumes of hydrogen in combining with one volume of oxygen condensed to the extent of onethird, or in other words, two volumes of hydrogen and one volume of oxygen combine to form two volumes of steam. Hydrogen and chlorine unite with each other in the proportion of 1 and 1, whilst ammonia gas is found to contain three of hydrogen to one of nitrogen by volume. But the student may ask which of the views are we to acceptDalton's, the combination by atoms, in which combination takes place by definite weights, or Gay-Lussac's law of volumes; are both correct, does one hinge upon the other and so confirm the statements contained therein, kinds, such as the shark-like Gyracanthus (twisted spine), and saurians of various species are found in the different strata of the group. Above the mountain limestone we come upon the upper or true coal-measures, a formation so valuable to commerce and industry as to make it one of the most sought after of nature's products. It consists of alternating strata of millstone grit, sandstones, clays, black shales, ironstone, and limestone; between which are found the seams of the carbonized vegetable remains called coal. The strata of this series are generally inclined at a very great angle to the horizon, and in some localities, as at Bristol, are formed into a basin shape. This is of course a great advantage to the miner, who is thereby saved the trouble and expense of sinking deep shafts. The fossils of the group are again of a freshwater character, like those of the lower coal measures; sauroid fishes and true saurians, in some cases amphibians, appear for the first time in this portion of the crust, and terrestrial animals of the frog kind have been presents one of the smaller machines suitable for or are they entirely separate theories? The found in various places; estuary shells are also working on a lathe. Many attempts at wood-carv- former view is correct, one theory fully con |