« PreviousContinue »
GLASS-WORKING is a most necessary and useful part of the education of a student in practical science; and is certainly a very interesting branch of it. There are many divisions of glass-work ing, which I shall notice in succession.
Save all the pieces of window-glass, broken wine-glasses, tumblers, and bottles that you can, because they may all be converted into some useful temporary apparatus; or will serve for you to commence operations upon. Waste must not be permitted in the laboratory any more than in any other department of your establishment; indeed, it is there that economy should be more rigidly practised. 1. Glass-cutting is one of the operations required to be practised by the student, and on that account we shall commence with it. There are several methods of cutting glass, but they may be arranged under three heads: 1st. By means of heat applied so as to produce a sudden change of temperature. 2nd. By means of scratch-old ing or cutting-tools. 3rd. by the combination of the two first processes.
Flint scratches glass very nicely, and is useful for marking bottles, tubes, &c., and even for outlining the part to be cracked by heat.
The splintered edges of glass tubes, or glass of any kind, may be filed smooth, holes drilled with a common drill - bow and a sharp triangular-edged drill, holes enlarged with a file or drill, plates of glass sawn with a watch-spring saw; and almost anything cut from glass when the tools are freely moistened with oil of turpentine in which camphor has been dissolved.
When you use the file to cut a tube, make a small notch first, and then dip the file into water, and proceed to cut a circular trace round the tube; by this means it will break more evenly and easily, and the file works better when moistened with water. If the tube is large, proceed as above, and add a little emery or very fine sand to the water. Very small glass tubes in a state of fusion may be divided by a pair of common scissors.
2. Glass-blowing. If you have paid attention to directions given at pages 259 and 350, of vol. I. of the New Series, you will not have any difficulty in using the mouth blow-pipe. I would also wish you to remember my remarks at page 39, of the same volume, respecting the great care that is required in cooling glass too suddenly after it has been heated.
3. Kind of glass. When you can work well, always choose the best glass tubes; but until you can manage the various processes of bordering, widening, drawing out, &c., be content to practise upon any glass tubes or phials.
The best kind of tubes for working are hard glass or flint - glass. You may have them of any diameter from the one
In the fifth volume of the Old Series,
A small triangular file, or a piece of notched watch-spring fixed in a groove in a piece of wood, or even a piece of sharp flint, will be all that you require for the purposes of the laboratory, although you may occasionally have to use a piece of heated tobacco-pipe or iron wire, and the iron ring, mentioned and figured at page 40, of our last volume.
p. 113, the student will find ample direc-eighth of an inch or even less, up to one tions for cutting, drilling holes in, grind- inch or more, and of nearly any thicking, and writing upon glass, and therefore ness. In choosing tubing for glass-workonly a few remarks are required upon the ing, be sure to have it of an uniform subject of glass-cutting. thickness and diameter, particularly for blowing, and take care that there are not any bumps, specks, air-holes, or stripes. Bohemian white hard glass-tubing, and the French white soft tubing are the best kinds for chemical purposes, as they are free from lead: this is the reason flintglass cannot be depended upon for chemical researches.
4. To prepare tubes for working.-Remove all dirt, dust, and damp from the tubing before you attempt to work it, and this may be done either by blowing through it with a bellows or the mouth, passing some lamp - wick through it, or washing it. The humidity must be removed by carefully heating the tubes before the fire, or holding them above a spirit-lamp; but in both cases they must be placed perpendicularly. Grease may be removed by washing them first in soda
and water, and then rinsing them out in fresh water. When the tubes are clean and dry, mark them into the required lengths with a file, and lay them on the table ready for being worked.
5. How to hold the tubes in the flame.(See page 39 of Vol. 1, New Series.)
6. To make some glass stirring-rods.-Get a piece of solid glass rod from a glassblower's, and holding the part that is to be divided at a short distance from the end of the flame, keep turning it round until it gets uniformly heated and soft; then pull it gently with both hands until it becomes like the part a in the upper figure in § 8. Allow it to cool gradually, then divide it with a file, and hold the ends in the flame until they are round and smooth.
7. To form borders to glass-tubes.-Take a piece of glass- tubing, cut it into pro
per lengths as directed before, and having selected one length, hold it in the flame of the lamp until it begins to soften, then insert a thick iron wire, or the smooth end of a warm glass rod into the mouth of the tube, and holding it steadily, turn the tube round with the other hand, so as to maintain an equal pressure upon the softened edge, as in the above figure. Care must be taken to press the edge outwards without exerting too great a degree of force at one time more than another, otherwise the bordering will look lumpy and clumsy.
8. To make a few test-tubes and drawingout generally. Having selected a piece of tubing about eight inches long and of the required diameter (from ths to ths or of an inch,) hold the central part over
the flame of a spirit-lamp, in the manner directed at page 39, Vol. I., New Series.
When the tubing begins to soften, gradually draw out each end, taking care to turn the tubing round and round, so as to expose every part of the centre of it to the influence of the flame of the lamp. It will then appear as a in the upper figure; and as the heat is continued to a cherry heat, and the force kept up, the one piece is gradually drawn out until like b in the figure, when it is rapidly turned round and the thin thread of glass fused. By this means the bottom of the test-tube becomes almost smooth and round, but as there is still a little lump left in the centre of the bottom, it should be held in the flame of the lamp until it disappears, care being taken all the time to turn it round. If the bottom is flattened, blow gently into the tube while it is hot, so as to swell out the bottom to a round shape.
If you now heat the irregular part of the other tube, and lay hold of the small end with a pair of pincers, or twist a fine iron wire over it and then pull it out gradually, you can finish off the remainder of the tubing.
Be careful always to draw the tubing apart in a straight line, otherwise it makes the ends of the test-tubes ill-shapen; and if the tube is long, place the right hand below the tube, and the left hand above. While manipulating, never heat too much of the central part of the tube, as it causes the test-tubes to be awkward, and wastes the glass.
When you want to draw out a point from the side of a tube, bottle, or glass, direct the flame of the blow-pipe to that particular portion, and maintain the heat until it becomes cherry red. Then apply the end of a piece of heated spare tubing, and keeping up the heat, solder the two together, allow it to cool a very little, and proceed to draw out as usual, when it will appear as in the figure above. Remove the irregular tapered end by means of a file, when it is cool, and afterwards solder a fine tube to the projecting part. By carefully attending to these instructions, the reader will be enabled to exercise his ingenuity with pleasure, and derive, at the same time, much practical experience.
BY W. J. K.
MAN in his miserable ignorance formerly considered that the vast chain of Nature was broken, and that some of the links were lost; but an All-wise Being has since permitted some of these connecting links to be discovered.
That there are connecting links there cannot be a doubt; for any person that has paid the least attention to the study of Natural History, must have observed them. Let us take the bat for example: it is virtually an animal, but is nevertheless furnished with wings, the surface of which is equally or more extended than in those of birds. They fly very high, and can guide themselves readily, although flying with great rapidity. The hindlegs, head, and tail of the skeleton indicate that it is an animal, even supposing that we did not know it was covered with fur; but if we examine the fore-part of the framework it appears more like that of a bird. Can we doubt, then, that the bat forms a connecting link between the birds and beasts? Again; let us take the seals, for example: they are undoubtedly animals; the body is covered with fur, the head shaped like a dog, &c.; but, then, they have the fore-feet shaped somewhat like a fin, and enveloped in the integuments of the body as far as the wrist, while the hinder-feet are enveloped almost to the heel and placed in such a manner, with a short tail between them, that they appear more like the tail of a fish than the hinder part of a beast. There are many other examples we could mention, particularly that curious animal of New Holland, called the Ornithorhynchus, or Platypus, but more commonly the duckbill: yet, having said thus much, we shall now proceed to describe one of the most curious vegetable productions with which we are at present acquainted-the vegetable or bulrush caterpillars of New Zealand and New South Wales, which form the connecting link between the animal and vegetable kingdoms. In this case, the caterpillar, instead of advancing, and being metamorphosed into a butterfly, retrogrades, and originates a plant.
These caterpillars are found in New Zealand in a light peaty soil, occurring
in certain districts where the Rata-trees, upon which it feeds during its lifetime, are to be found with the caterpillars suspended. Those discovered in New South Wales were found in a rich dark alluvial soil on the banks of the Murrumbidgee river.
The natives of New Zealand call the vegetable caterpillar Ameto - Hotete, and when it is fresh they eat it, burning the top, and rubbing the ashes, when reduced to a fine powder, into their recently tatooed bodies. They consider that the ashes of this plant are more indelible than any pigment.
The New Zealand caterpillar is named the Sphoria Robertsia, and is usually about three inches and a half in length, although many specimens are considerably less. When seen, as in the accompanying figure, it looks somewhat like a silkworm that has been dipped in a reddish kind of earth and dried, having a stem from six to ten inches long issuing from the head. When we turn the insect-plant over, we observe the feet, the segments of the body, the mandibles, claws, and horny part of the head, exactly the same as in the living specimen the only difference is the colour and a slightly shrivelled appearance.
When the plant is discovered, only a small portion of the stem is seen above the ground, the remainder being always buried far beneath the surface; its appearance is most singular there are not any leaves or flowers to be seen, only a dry stump with the chief of the bulrush on the end, sticking above the ground; and when it is exhumed, the body is soft, and the stem somewhat succulent. On dividing the body longitudinally, we can observe the intestinal canal very plainly, provided the section be made soon after its exhumation.
It is very seldom that these plants have more than one stem proceeding from each; but occasionally we have observed two,-as in the specimen now before us (f, d)-each stem terminating in a kind of bulrush-head, which exhibits the appearance shown in the figure c, when highly magnified. If one of these stems is broken off while the plant is yet alive, another springs from it,- -as in the figure b, where the round portion on the left represents the old stem, while the other is
seen shooting off to the right. As soon as the plant has arrived at maturity, it speedily withers and decomposes.
The caterpillars found in New South Wales are about six inches long, and the plant about half as long again, or sometimes only the same length. They have been named the sphaeria innominata, or unnamed sphoria. These plants have a thick stem, which looks somewhat like a beet-root, and is formed by several stalks uniting at the top, which is surrounded by a kind of velvety-looking fringe, which appears like a full blown flower when seen above the ground on the banks of the Murrumbidgee river.
These cryptogamic-plants are produced from the nape of the neck of the caterpillar; and there is no doubt that the process of vegetation commences during the life of the caterpillar; because we cannot discover any indications of decay in its structure, and it is therefore more than probable that, previous to the period when these insects are metamorphosed into a chrysalis, the caterpillar, in en
a, Sphoria Robertsia of New Zealand, nearly one fourth of the natural size, showing the under part of the caterpillar and the stem proceeding from the head and terminating in the bulrush; b, The head of the caterpillar, showing the stem proceeding from between the scales of the neck and also the two stalks from one root; c, A portion of the apex of the stem magnified, showing the arrangement of the bulrush; d, A caterpillar with two stems proceeding from the head, engraven half the natural size; e, The Sphæria Innominata of New South Wales, one-fourth the natural size; f, Bulrush, apex of the stems of a Sphæria Robertsia.
deavouring to crawl into the earth, gets one or more of the seeds of the fungus (which, like the viscus quercus, or misletoe, is a parasite) between the scales of its neck, and that the seed is either the cause of its death, or else hastens it. It is reasonable to suppose that the warmth of the body of the insect assists in the germinating process; and further, that the plant derives its nourishment from the adipose, or fatty tissue of the insect, and not from the adjacent soil.
Professor Owen, of the Royal College of Surgeons of England, believes that the insect is attacked with the parasite previously to its being buried in the earth; while Sir William Hooker is of opinion, that the caterpillar is attacked by the parasite after it has buried itself and died.
Although the specimens we have had engraven above are exceedingly curious and highly interesting, yet there is another insect, found in the West Indies, which is perhaps even more curious-we mean the vegetating wasp.
of Count Louis, which he had never entertained before.
In his daily rambles about the adjoining lands, he had heard much of the goodness and charity of the young lady at the castle; and willingly deceived by his own wishes, and the glowing descriptions of the grateful people, believed that it was Ada of whom they spoke, forgetting that the gay beauty was almost constantly surrounded by a swarm of flatterers, who left her little time or inclination to seek out the destitute; while to the partial eye of gratitude, a benefactor is very apt to appear in the guise of an angel.
Among the homes of the poor where the Count visited, was one where dwelt an infirm man and his invalid wife; they suffered much from privation and illness; and the generous nobleman often assisted them. He heard much of the charitable young lady who aided the suffering wife, and helpless children so kindly and cheerfully, and often wished to meet her on her errand of mercy. He doubted not that this good angel was Ada, and fondly hoped that such noble qualities would in time obliterate what he considered her greatest fault.
The poor man had brought with him from his native France, a little root of mignonette, which was planted in the small garden spot, and grew luxuriantly, filling the air with its sweet breath. The sick wife loved to inhale the reviving odour; it recalled thoughts of home, and often, in speaking of her benefactress, the poor woman would say,
"Her very presence revives me; she is like my mignonette."
Upon returning from the cottage one day, where he had heard a tearful relation of the blessed lady's goodness in passing all the night by the bedside of the suffering invalid, the Count determined to hesitate no longer, but declare his hopes at once; his heart was full of admiration and esteem, and the trifling manners which had displeased and annoyed him, he now considered merely a screen to conceal her real worth from notice. He never even dreamed that Sybil-plain, unassuming, humble Sybil--could appear to any one like an angel of beauty; he had scarcely thought about her at all, so how should he? When he entered the saloon he found