In the general collection of objects which accompany microscopes from the opticians, there is usually a great paucity of those of a vegetable origin, and should they be purchased separately they are generally but little to be depended upon, even for names -less for showing the organic structure of the plants. It is but seldom that amateurs can supply themselves with these very interesting objects, for two reasons; one because the amateur, unless a botanist, knows not how to select them; or knowing this, he is not aware of the simple methods employed to prepare such as are to be shown in sections. We, therefore, trust that science may be promoted, and amusement increased, by a description of a machine for cutting sections of wood for the microscope, and by making a few remarks upon the vegetable organization displayed by those sections, when viewed by the transmitted light of the instrument.

Fig. 1.-A is a thick plate of brass, about eight inches long and three inches wide, ground perfectly level at the top, and supported by four legs, which rest upon a rather larger board below. B is a ridge of brass, fastened on one side of A, and standing

a guide C is a

up about half an inch. This is intended as for the tool afterwards to be described. cylindrical socket of brass, fastened to the underside of A, and projecting above the upper surface, about an eighth of an inch. On the lower part of C is a female screw, in which the male screw, attached to the cog wheel E, moves up and down. D, and also Fig. 4, is a solid cylinder of brass, fitting accurately, but easily, into the hollow of C, which hollow it also corresponds to in length-it has a hole, about half an inch square down the centre. Into this hole the wood to be cut is fastened, by means of a small wedge driven into the notches, represented on one side of it. Thus D, with the wood within it, moves up and down as the screw below is turned one way or the other, and according to the relative size of the screw thread, compared to the number of notches on the cog wheel, so D will be elevated at pleasure, and the wood within it cut to any degree of tenuity, even to so little as the five-hundredth part of an inch in thickness. F is an arm of brass, which extends downwards for the purpose of holding the spring G-the object of which is to shut in between

two of the cogs, and to hold the wheel E firm while a section is being made; also, to insure steadiness in the wood itself when the knife passes over it. On the outside of D is placed a stud, which moves up and down in a groove cut in C, and which is seen as a small square black mark on the upper part.

Fig. 2 is the knife employed. A is a frame of brass, five inches and a half long, ground very accurately level at the bottom and side-upon this is fastened a steel knife, with a broad blade and keen edge; it is attached by a thumb-screw, (a section of which is seen at Fig. 3,) at each extremity

of the frame.

When the machine is to be used, the wood is to be prepared by soaking it in water for some hours, according to its condition or hardness, and fixed into the square hole prepared for it, so as to stand a quarter of an inch above the surface of D-turn backwards the screw E, so that D shall descend as much as possible. Then oil the surface of A, and place the knife and frame, Fig. 2, upon it, (having placed the machine upon a table, and standing at that end of it nearest A,)-slide the knife forward, and adjust the height of the wood so as just to meet the blade by the screw beneath. All is now adjusted. Hold back the spring with one fingerturn the wheel two or three notches, and let the spring fall back again. This having raised the wood a trifle, a section may be cut by passing the knife quite along over it. Draw the knife back, project the wood as before, and pass the knife along, and a second section is, in like manner, produced; and thus until all the wood is shaved away. only care requisite is to have the knife very sharpto hold it steadily by means of the thumb-screwsand to regulate the thickness of the cuttings by turning the cog wheel, more or less, according to circumstances, as may be found best to succeed.

The

The sections should generally be about a threehundredth part of an inch in thickness, and as a general criterion to know their quality, it may be observed, that if they float in water they will be good, if not, they must be rejected as useless. A regular degree of thickness throughout is also requisite. After being cut the sections should be cleared of all extraneous matter-if they are from the stems of herbaceous plants, soaking for a few minutes in a wine glass of warm water will suffice -if of resinous substances, immersion in boiling alcohol is advisable; and boiling nitric acid, supposing the whole should be hard and fibrous, may often be used to advantage.

Some persons content themselves with the transverse section of a branch or stem, desiring only to witness the general arrangement of the vessels; but these convey only a partial idea of the real character of vegetable organization, and, in some instances, tend to mislead rather than to instruct, as without longitudinal sections the true nature of the vessels cannot be ascertained. The philosophic inquirer will choose to have three sections, that he may examine nature under every aspect-one cut transversely, and two longitudinal: one of which is to be in the direction of the medullary rays: that is, from the centre of the stem to the bark, and the other at right angles to this, near the bark. These three cuttings will show the state and position of all the vessels throughout.

ASPHALTE.

ASPHALTE is a species of pitchy or bituminous stone, which, in ancient times, was much used as a cement in building, and which, of late years, has been recommended to public notice, as excellently adapted for covering floors, roofs, for flagging, and for various other useful purposes.

On examining the valley of Travers, in the Prussian province of Neufchatel, about the year 1712, an ingenious, learned, and speculative Greek, named Eirinis, discovered a fine bed of asphaltic rock, and, probably from some recollections suggested to him by his knowledge of antiquity, began to make experiments upon the value of the rock for cementing purposes. He describes this rock, or asphalte, as he called it, to be "composed of a mineral substance, gelatinous and calorous, more clammy and glutinous than pitch; not porous, but very solid, as its weight indicates; and so repelling the influence alike of air, cold, and water, that neither can penetrate it; it is better adapted than any other substance to cement and bind buildings and structures of every kind; preserving the timber from the dry rot, from worms, and the ravages of time; so much so, that exposure to the most inclement extremes of weather only renders it the firmer and the more enduring." Such is the account given by Eirinis of his asphaltic cement; and he also states that its efficacy and durability were tried and proved on many buildings in France, Neufchatel, and Switzerland. "Nothing, (says he) can be easier than the composition of this cement," and he gives directions for melting it as it is taken from the mine, and stirring it when melted, mixing with it at the same time ten per cent. of pitch, after which it is to be spread on the stone or wood to be coated, previously heated to a slight degree.

Such was the first attempt made, in modern times, to turn the natural production, called asphalte, to service in building. Eirinis was not supported properly, however, and the Val de Travers mines, though occasionally wrought by succeeding speculators, have only fallen into competent hands within a very recent period. Count de Sassenay, who had acquired the requisite experience by his having been for six years the proprietor and manager of the Seyssel mines, became, in the beginning of 1838, the proprietor of those of the Valley of Travers, in Neufchatel. The Seyssel mines, it is to be observed, are also asphaltic, and have been wrought for a number of years. But, on examination, Count de Sassenay found the Neufchatel mines to contain a finer-grained rock, and with two per cent. more of bitumen in it than the Seyssel mines. He was therefore led to become the purchaser of the former, and has established a company at Neufchatel, with a capital of forty thousand pounds, for the working of asphalte, and for its sale in the various countries around.

Count de Sassenay states, in the Introduction to a little pamphlet which supplies us with these particulars, that there are two kinds of mineral matter which go by the name of asphalte, though erroneously so. The first is an earthy concretion of gritty, loose texture, to which the Count gives the name of bituminous molasse, and which he ascribes to the latest or tertiary formation of rocks. The other substance is the true asphalte, which is solid, of the color of soot, and is an admixture of bitumen with calcareous or limestone rock of the Jura formation, which belongs to the secondary era.

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The bitumen is here completely combined or amalgamated with the calcareous material, and this union is productive of a new homogenous substance, which alone is the true asphaltic cement, or asphalte. Bituminous molasse is a mineral substance, comparatively abundant on the continent, and has been wrought in several places with the view of making the same cement, but has not undergone that natural admixture with calcareous matter which constitutes the true asphalte, and hence such views have not been realized. This is not only stated by Count de Sassenay, but by M. Rozet, M. H. Fournel, (a noted engineer,) and other observers. "Many experiments have been made to imitate the cement we have mentioned, (that of Seyssel;) but in these operations the want of the calcareous matter has been attempted to be supplied by substances, which absorbing the bitumen, produce a composition which cannot resist the influence of heat or cold, but is melted by the sun and cracked by the frost." The Val de Travers, where are found the finest kinds, as has been said, of this natural production, formed in all probability under strong volcanic action, leads into the Lake of Neufchatel. Half-way up the mountain-sides, the asphaltic works are carried on. "The operations,' says M. Fournel, are very simple, and consist merely in blasting the rock. The cavities for the powder are perforated by wimbles of about thirty-nine inches in length, one of which a man can work as he would a carpenter's auger. This manner of boring oppears to be applicable only to the asphaltic stone. The labourers can work better in winter than in summer; because the rock being harder and more condensed in cold weather, the powder has more effect, and the blasting is more extensive." The rock is in blocks or irregular masses not in strata, and there is reason to believe that the whole mountain is of asphalte. The manner of preparing the rock for cementing purposes is this. "Ninety-four parts (weight) of the asphaltic stone, pulverised, are mixed with six parts of bitumen, and melted down in large boilers; and the mass is then poured off, and formed into rectangular cakes, which are sold as the asphaltic cement." It is easily re-melted, and instead of losing, gains quality by the repetition of the process. Of late, however, the plan has been adopted of sending the stone itself to the place where it is to be used, and there melting and mixing it with the tar immediately before use. This saves one melting. The way of using it requires little explanation. When melted, the cement is merely spread over the desired part equally, and in such thickness as circumstances may require. In the coating of places to be trodden much, such as footways, terraces, slabs, &c., it is customary to mix fine river sand with it, which gives it more stability, and a degree of roughness that is not unneces

sary.

We have now to ask if the asphaltic cement has been extensively tried, and with what issue. Count

de Sassenay, when proprietor of the Seyssel mines obtained permision to use the cement in the fortifications of Vincennes, Douay, Grenoble, and Besançon. The Minister of War was satisfied by the experiment that it would be highly advantageous to have the roofs, floors, &c. of barrack rooms coated both on the score of cleanliness, (inasmuch as the cementing was easily washed,) and on account of the protection against damp afforded by it. It was also found that rats and mice disappeared where the cement was laid down. On these facts being ascertained, the French Minister of War contracted for

the use of asphalte in the various buildings over which he had control. The extensive commissariat magazines at Bercy, and those which supply the garrison of Paris, the roofs, ceilings, and floors of the detached forts at Lyons, the arsenal at Douay, the new barracks at Peronne, those at Mont Louis and other places, were all supplied with asphaltic coatings, in whole or in part. Asphalte was also substituted for the stone pavement in some of the cavalry barracks. The unwearibility of the materials rendered these experiments most satisfac tory. [A staircase, coated with the cement by Eirinis more than a hundred years ago, still remains, and is unmarked, whereas contemporary stone stairs in the same building are hollowed out by footmarks.] The Ministers of the Marine and of the Interior in France followed the example of the War Minister, and coated their convict-prisons and other edifices with the asphalte, and with equal satisfaction.

These things passed very recently-subsequently, indeed, to the year 1832-when Count de Sassenay became proprietor of the Seyssel mines, from which the asphaltic cement was procured for the purposes mentioned. It was not till 1835 that any experiment was made upon the use of asphalte for flagging thoroughfares. At that time the footway of the Pont Royal was coated with the cement, and its durability, under the tread of thirty thousand people daily, has amply justified the trial. Since that time, the footway of the bridge Du Carousal, the footway by the railings of the Tuilleries, other footways, and the basin of the fountain in Richelieu Street, have been coated with the asphaltic cement, and it has been found to stand equally well the "summer's heat and winter's snow.' The Belgians have begun also to use the article extensively in public works. In several parts of London, portions of the street for foot passengers have also been laid with asphaltum, by way of experiment, and it seems to answer all the purpose of flag-stones. Various artificial cements, in imitation of the natural asphaltic, have been brought before the public, but, on trial, they have been found to crack in winter, and to melt in summer-in short, to be totally inefficient in comparison. The asphaltic cement has been used with success in joining stone to stone, or metal to stone. As for its use in the caulking of vessels, we are not aware what has been the result of recent experiments on this point. The induration which forms its chief value in coating pavements and such places, might be injurious in the case of vessels, but an additional proportion of tar to the cement would probably amend this fault and render it useful there also.

CUTTINGS IN WATER,

(Resumed from page 142, and concluded.) THE art of propagating plants by cuttings, embraces a vast number of very interesting facts, some of which will hereafter be noticed as they appropriately occur. The method to which we now solicit the attention of our ameteur readers is despised by the professional gardener, as being beneath his skill and attention; nevertheless it will not be difficult to show that the instruction which it conveys is in itself amply sufficient to rescue it from contempt, or rather to raise it high in the estimation of the lover of nature.

The three spring months comprise the period wherein cuttings succeed most freely; and for the reason that they are then inclined to start into

growth, and to obey the increasing stimulus of solar light; but they are not inactive during the summer, and many cuttings of the hard-wooded species prosper most when they are placed in a cool situation late in autumn. They thus retain their vital power during winter, gradually form a callus, or granulated mass, between the bark and wood, and finally develop roots when gently excited by heat in the early spring.

A cutting is prepared by passing a knife either through or close under a joint or leaf; and it almost invariably is found that, if a young shoot be slipped off the parent plant, and carefully trimmed at the heel to remove asperities, and render the surface smooth, roots will be produced much more freely than they would be from any intermediate part; for a number of minute embryo buds exist round the base of a shoot or twig just at the point of its junction with a larger branch. These buds or germs seem peculiarly inclined to protrude root processes, while those seated among the leaves of the upper part tend directly to expand into shoots. But when a cutting is fixed in the soil, whether it be in a spot or in the open ground, its progress is concealed, and can be only conjectured by the appearance of that part which remains above the surface. This forms one objection; another is found in the trouble which attends the plunging in heat, the covering with a hand or bell glass, and the necessity of guarding against mouldiness or damping off, by frequently ren'oving and wiping that glass. A cutting when placed in a phial of water may fail; it may also decay; but, if it is to succeed eventually, two circumstances will become obvious-first, it will not flag or droop, though no glass covering be put on it; and second, the water, however long the cutting remain over it, will show little if any tendency to become fetid or offensive. Every one must have remarked the extreme fetor acquired by water in which flowers are placed; therefore the contrast exhibited by the fluid in which a vegetating and growing plant remains during several weeks, exposed perhaps to the occasional heat 95-100 degrees, is equally extraordinary and pleasing; there may be found exceptions; but they have not come under our notice, and we have had not a little experience for many years.

It has long been an observed fact that the oleander (Nerium) will emit roots, if a young green shoot of it be placed in a small bottle of water, exposed either to the sun-heat of a window or to the warm atmosphere of a hot-bed frame or forcing house. It frequently happens that a lively shoot, with the flower-buds becoming visible at its summit, will take root in a few weeks, and being then transferred to a pot of suitable earth, in heat, will retain and expand its flowers, forming a beautiful object in minature.

Some

The succulents root freely; so does the balsam. Of the last-named plant, specimens have been produced in a few weeks, with several expanded flowers, although the parent plant did not exhibit the slightest signs of coming into bloom. cuttings of the cucumber and melon, taken at the third joint from the summits, or indeed from any part of the plants, rarely fail to root in a few days; and we entertain little doubt that a stock of succession plants for the frames can thus be obtained more readily than by any ordinary process; even single leaves protrude a mass of fibres, though it has not appeared that any latent bud became excited to form a shoot.

Among multitudes of examples we may cite the mints, the French willow, ruellia formosa, all the justicias which were subjected to trial, heliotrope, petunia, &c. as generally free rooters. Dahlia is arbitrary, and so is erythrina crista-galli, or taurifolia; but they succeed after depositing masses of a species of parenchymatous matter. The Gesnereaceæ, particularly gloxinia speciosa and candida, rarely fail. The careful observer will perceive in the two last a gradual convexity of form at the base of the cutting; it is the origin of the future tuberous mass, and from it small glittering fibres emerge which appear like glass threads; nothing can exceed the interest possessed by this charming object.

Among shrubs we have tried successfully the common geranium, or pelargonium, the dark China rose, begonia, coronilla, &c.

Not to dwell upon the instruction to be derived from the observation of processes which stand revealed to the eye, we do contend that as, in removing these rooted subjects from their fluid element, no injury is done the slightest fibre or most delicate spongeole, a great object is attained; for the plants, if treated with any degree of skill and dexterity, strike off at once, and establish themselves in an appropriate soil with the least possible loss of time.

FIRING GUNPOWDER BY ELECTRICITY. UNTIL within these few years one of the most difficult and uncertain experiments in electricity was the firing of gunpowder. A method of accomplishing this with great facility and absolute certainty we owe to Mr. Sturgeon, who is well known to have contributed so largely to the development of electrical science, and the improvement of electrical appa

ratus.

Formerly it was the practice to pass the shock of a powerful battery through a tube of water, by which means the gunpowder placed between the wires of the universal discharger was sometimes fired, but more often not-if the shock was too powerful the gunpowder was scattered-if the glass tube was too small the gunpowder remained untouched, and the glass tube was exploded-if too large the shock passed through without effect upon any part of the apparatus, as was the case also when a metal wire took the place of the tube of water.

Arguing from these facts, Mr Sturgeon was led to conclude, that the reason why water was at all necessary, was because it retarded the electric fluid until it had time to act upon the combustible, water conducting it with infinite less rapidity then metalthus water, or some similar imperfect conductor, was necessary. Also the experiments with the large and small glass tubes, proved that the shock, although retarded in its course, must remain concentrated, and, therefore, the smaller the channel of water the greater certainty of success, though, at the same time, the danger of explosion was materially increased. To obviate these difficulties, Mr. Sturgeon thought to substitute for the water tubes, a string or thread, dipped in water. With so much success was this attended, that he was enabled to fire gunpowder at all times, with positive certainty and safety, even when employing a Leyden jar of not more than about a quart capacity. The form of one machine for this purpose may be seen as follows: