Scientific American Supplement, No. 803, May 23, 1891(txt+pdf+epub+mobi电子书下载)

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Scientific American Supplement, No. 803, May 23, 1891

Scientific American Supplement, No. 803, May 23, 1891试读:

THE GREAT EQUATORIAL OF THE PARIS OBSERVATORY.

The great instrument which has just completed the installation of our national observatory is constructed upon the same principle as the elbowed equatorial, 11 in. in diameter, established in 1882, according to the ingenious arrangement devised as long ago as 1872, by Mr. Loewy, assistant director of the Paris Observatory.

We shall here recall the fact that the elbowed equatorial consists of two parts joined at right angles. One of these is directed according to the axis of the world, and is capable of revolving around its own axis, and the other, which is at right angles to it, is capable of describing around the first a plane representing the celestial equator. At the apex of the right angle there is a plane mirror of silvered glass inclined at an angle of 45 deg. with respect to the optical axis, and which sends toward the ocular the image coming from the objective and already reflected by another and similar plane mirror. The objective and this second mirror (which is inclined at an angle of 45 deg.) are placed at the extremity of the external part of the tube, and form part of a cube, movable around the axis of the instrument at right angles with the axis of the world. The diagram in Fig. 3 will allow the course of a luminous ray coming from space to be easily understood. The image of the star, A, toward which the instrument is directed, traverses the objective, B C, is reflected first from the mirror, B D, and next from the central mirror, E F, and finally reaches O, at the ocular where the observer is stationed.FIG 3.—DIAGRAM SHOWING THE COURSE OF A LUMINOUS RAY IN THE GREAT EQUATORIAL.

This new equatorial differs from the first model by its much larger dimensions and its extremely remarkable mechanical improvements. The optical part, which is admirably elaborated, consists of a large astronomical objective 24 in. in diameter, and of a photographic objective of the same aperture, capable of being substituted, one for the other, according to the nature of the work that it is desired to accomplish by the aid of this colossal telescope, the total length of which is 59 ft. The two plane mirrors which complete the optical system have, respectively, diameters of 34 in. and 29 in. These two magnificent objectives and the two mirrors were constructed by the Brothers Henry, whose double reputation as astronomers and opticians is so universally established. The mechanical part is the successful work of Mr. Gautier, who has looked after every detail with the greatest care, and has thus realized a true chef d'oeuvre. The colossal instrument, the total weight of which is 26,400 lb., is maneuvered by hand with the greatest ease. A clockwork movement, due to the same able manufacturer, is capable, besides, of moving the instrument with all the precision desirable, and of permitting it to follow the stars in their travel across the heavens. A star appearing in the horizon can thus be observed from its rising to its setting. The astronomer, his eye at the ocular, is always conveniently seated at the same place, observing the distant worlds, rendered immovable, so to speak, in the field of the instrument. For stars which, like the moon and the planets, have a course different from the diurnal motion, it is possible to modify the running of the clockwork, so that they can thus be as easily followed as in the preceding case. Fig. 1 gives a general view of the new installation, for which it became necessary to build a special edifice 65 ft. in height on the ground south of the observatory bordering on the Arago Boulevard. A large movable structure serves for covering the external part of the instrument. This structure rests on rails, upon which it slides toward the south when it is desired to make observations. It will be seen from the figure how the principal axis of the instrument rests upon the two masonry pillars, one of which is 49 ft. and the other 13 ft. in height.FIG 1.—THE GREAT EQUATORIAL OF THE PARIS OBSERVATORY.

The total cost of the pavilion, rolling structure, and instrument (including the two objectives) will amount to about $80,000 after the new equatorial has been provided with the scientific apparatus that necessarily have to accompany it for the various and numerous applications to which the use of it will give rise.FIG 2.—OCULAR OF THE GREAT EQUATORIAL.

Fig. 2 shows us the room in the observatory in which the astronomer, seated in his chair, is completely protected against the inclemencies of the weather. Here, with his eye applied to the ocular, he can, without changing position (owing to all the handles that act at his will upon the many transmissions necessary for the maneuvering), direct his instrument unaided toward every point of the heavens with wonderful sureness and precision. The observer has before him on the same plane two divided circles, one of which gives the right ascensions and the other the declinations, and which he consults at each observation for the exact orientation of the equatorial.

All the readings are done by the aid of electric lamps of very small dimensions, supplied by accumulators, and which are lighted at will. Each of these lamps is of one candle power; two of them are designed for the reading of the two circles of right ascension and of declination; a third serves for the reading of the position circle of the micrometer; two others are employed for the reading of the drums fixed upon the micrometric screws; four others serve for rendering the spider threads of the reticule brilliant upon a black ground; and still another serves for illuminating the field of the instrument where the same threads remain black upon a luminous ground. The currents that supply these lamps are brought over two different circuits, in which are interposed rheostats that permit of graduating the intensity of the light at will.

Since the installation of the first model of an elbowed equatorial of 11 in. aperture, in 1882, at the Paris Observatory, the numerous and indisputable advantages of this sort of instrument have led a certain number of observatories to have similar, but larger, instruments constructed. In France, the observatories of Alger, Besancon, and Lyons have telescopes of this kind, the objectives of which have diameters of from 12 in. to 13 in., and which have been used for several years past in equatorial observations of all kinds. The Vienna Observatory has for the last two years been using an instrument of this kind whose objective has an aperture of 15 inches. Another equatorial of the same kind, of 16 in. aperture, is now in course of construction for the Nice Observatory, where it will be especially employed as a seeker of exceptional power—a role to which this kind of instrument lends itself admirably. The optical part of all these instruments was furnished by the Messrs. Henry, and the mechanical part by Mr. Gautier.

The largest elbowed equatorial is, therefore, that of the Paris Observatory. Its optical power, moreover, corresponds perfectly to its huge dimensions. The experimental observations which have already been made with it fully justify the hopes that we had a right to found upon the professional skill of the eminent artists to whom we owe this colossal instrument. The images of the stars were given with the greatest sharpness, and it was possible to study the details of the surface of the moon and other planets, and several star clusters, in all their peculiarities, in the most remarkable manner.

When it shall become possible to make use of this equatorial for celestial photography, there is no doubt that we shall obtain the most important results. As regards the moon, in particular, the photographing of which has already made so great progress, its direct image at the focus of the large 24 in. photographic objective will have a diameter of 11 in., and, being magnified, will be capable of giving images of more than 3 ft. in diameter.—La Nature.

LILY OF THE VALLEY.

There is no flower more truly and universally popular than the lily of the valley. What can be more delicious and refreshing than the scent of its fragrant flowers? What other plant can equal in spring the attractiveness of its pillars of pure white bells half hidden in their beautiful foliage? There are few gardens without a bed of lily of the valley, but too often the place chosen for it is some dark corner where nothing else would be expected to grow, but it is supposed as a matter of course that "it will do for a lily bed." The consequence is that although these lilies are very easy things to cultivate, as indeed they ought to be, seeing that they grow wild in the woods of this and other countries, yet one hears so often from those who take only a slight interest in practical gardening, "I have a lily bed, but I scarcely ever get any lilies." Wild lilies are hardly worth the trouble of gathering, they are so thin and poor; it is interesting to find a plant so beautiful and precious in the garden growing wild in the woods, but beyond that the flowers themselves are worth but very little. This at once tells us an evident fact about the lily of the valley, viz., that it does require cultivation. It is not a thing to be left alone in a dark and dreary corner to take care of itself anyhow year after year. People who treat it so deserve to be disappointed when in May they go to the lily bed and find plenty of leaves, but no flowers, or, if any, a few poor, weak attempts at producing blossoms, which ought to be so beautiful and fragrant. One great advantage of this lovely spring flower is that it can be so readily and easily forced. Gardeners in large places usually spend several pounds in the purchase of crowns and clumps of the lily of the valley, which they either import direct from foreign nurserymen or else procure from their own dealer in such things, who imports his lilies in large quantities from abroad. But we may well ask, Have foreign gardeners found out some great secret in the cultivation of this plant? Or is their climate more suitable for it? Or their soil adapted to growing it and getting it into splendid condition for forcing? It is impossible that the conditions for growing large and fine heads of this lily can be in any way better in Berlin or elsewhere than they are in our own land, unless greater heat in summer than we experience in England is necessary for ripening the growths in autumn.

There is another question certainly as to varieties; one variety may be superior to another, but surely if so it is only on the principle of the survival of the fittest, that is to say, by carefully working on the finest forms only and propagating from them, a strong and vigorous stock may be the result, and this stock may be dignified with a special name. For my own part what I want is to have a great abundance of lily of the valley from February till the out-door season is over. To do this with imported clumps would, of course, be most costly, and far beyond what any person ought to spend on mere flowers. Though it must be remembered that it is an immense advantage to the parish priest to be able to take bright and sweet flowers to the bedside of the sick, or to gratify the weary spirit of a confirmed invalid, confined through all the lovely spring time to the narrow limits of a dull room, with the fragrant flowers of the lily of the valley. I determined, therefore, that I would have an abundance of early lilies, and that they should not be costly, but simply produced at about the same expense as any other flowers, and I have been very successful in accomplishing this by very simple means. First of all, it is necessary to have the means of forcing, that is to say the required heat, which in my case is obtained from an early vinery. I have seen lilies forced by pushing the clumps in under the material for making a hot bed for early cucumbers, the clumps being drawn out, of course, as soon as the flowers had made a good start. They have then to be carefully and very gradually exposed to full light, but often, although fine heads of bloom may be produced in this way, the leaves will be few and poor.

My method is simply this: In the kitchen garden there is the old original bed of lilies of the valley in a corner certainly, but not a dark corner. This is the reservoir, as were, from whence the regular supply of heads for special cultivation is taken. This large bed is not neglected and left alone to take care of itself, but carefully manured with leaf mould and peat moss manure from the stable every year. Especially the vacant places made by taking out the heads for cultivation are thus filled up.

Then under the east wall another piece of ground is laid out and divided into four plots. When I first began to prepare for forcing I waited four years, and had one plot planted with divided heads each year. Clumps are taken up from the reserve bed and then shaken out and the heads separated, each with its little bunch of fibrous roots. They are then carefully planted in one of the plots about 4 in. or 5 in. apart, the ground having previously been made as light and rich as possible with plenty of leaf mould. I think the best time for doing this is in autumn, after the leaves have turned yellow and have rotted away; but frequently the operation has been delayed till spring, without much difference in the result.

Asparagus is usually transplanted in spring, and there is a wonderful affinity between the two plants, which, of course, belong to the same order. It was a long time to wait—four years—but I felt there was no use in being in too great a hurry, and every year the plants manifestly improved, and the buds swelled up nicely and looked more plump each winter when the leaves were gone. It must be remembered also that a nice crop of flowers could be gathered each year. When the fourth year came, the first plot was divided up into squares about 2 ft. each way, and taken up before any hard frost or snow had made their appearance, and put away on the floor of an unused stable. From the stable they are removed as required in the squares to the vinery, where they grow beautifully, not sending up merely fine heads of bloom without a vestige of leaf, but growing as they would in spring out of doors with a mass of foliage, among which one has to search for the spikes of flower, so precious for all sorts of purposes at that early season of the year.

The spikes produced in this way do not equal in thickness and substance of petal the flowers which come from more carefully prepared clumps imported from Berlin, but they are fine and strong, and above all most abundant. I can not only supply the house and small vases for the church, but also send away boxes of the flowers to friends at a distance, besides the many gifts which can be made to those who are ill or invalids. Few gifts at such a time are more acceptable than a fragrant nosegay of lily of the valley. In order to keep the supply of prepared roots ready year after year, a plot of ground has only to be planted each autumn, so that in the rotation of years it may be ready for forcing when its turn shall come.

As the season advances, as every one knows who has attempted to force the lily of the valley, much less time is taken in bringing the flowers to perfection under precisely the same circumstances as those in which the first sods are forced. In February or earlier the buds are more unwilling to start; there seems to be a natural repugnance against being so soon forced out of the winter's sleep and rest. But when the flowers do come, they are nearly as fine and their leaves are quite as abundant in this way of forcing as from the pieces introduced much later into heat. It would be easy to preserve the squares after all the flowers are gathered, but I found that they would not, like strawberries, kindly furnish forth another crop later on in the year, and, therefore, mine are flung away; and I have often pitied the tender leaves in the frost and snow after their short sojourn in the hot climate of the vinery. But the reserve bed will always supply an ample quantity of fresh heads, and it is best to take the new plants for preparation in the kitchen garden from this reserve bed.

This very simple method of forcing lilies of the valley is within the reach of any one who has even a small garden and a warm house, and these two things are becoming more and more common among us every day.—A Gloucestershire Parson, in The Garden.

[Continued from SUPPLEMENT, No. 802, page 12820.]

REPORT ON INSECTS

THE ONION MAGGOT.Phorbia ceparum (Meig.)

Early in June a somewhat hairy fly, Fig. 9, may be seen flying about, and depositing its eggs on the leaves of the young onion plants, near the roots, Fig. 10.

Dr. Fitch describes this fly as follows: "It has a considerable resemblance to the common house fly, though when the two are placed side by side, this is observed as being more slender in its form. The two sexes are readily distinguished from each other by the eyes, which in the males are close together, and so large as to occupy almost the whole surface of the head, while in the females they are widely separated from each other. These flies are of an ash gray color, with the head silvery, and a rusty black stripe between the eyes, forked at its hind end. And this species is particularly distinguished by having a row of black spots along the middle of the abdomen or hind body, which sometimes run into each other, and then forming a continuous stripe.

"This row of spots is quite distinct in the male, but in the female is very faint, or is often wholly imperceptible. This fly measured 0.22 to 0.25 inch in length, the females being usually rather larger than the males." The eggs are white, smooth, somewhat oval in outline, and about one twenty-fifth of an inch in length. Usually not more than half a dozen are laid on a single plant, and the young maggot burrows downward within the sheath, leaving a streak of pale green to indicate its path, and making its way into the root, devours all except the outer skin.

The maggots reach their full growth in about two weeks, when they are about one-third of an inch long, white and glossy, tapering from the posterior end to the head, which is armed with a pair of black, hook-like jaws. The opposite end is cut off obliquely and has eight tooth-like projections around the edge, and a pair of small brown tubercles near the middle. Fig. 11 shows the eggs, larva, and pupa, natural size and enlarged.

They usually leave the onions and transform to pupæ within the ground. The form of the pupa does not differ very much from the maggot, but the skin has hardened and changed to a chestnut brown color, and they remain in this stage about two weeks in the summer, when the perfect flies emerge. There are successive broods during the season, and the winter is passed in the pupa stage.

The following remedies have been suggested:

Scattering dry, unleached wood ashes over the plants as soon as they are up, while they are wet with dew, and continuing this as often as once a week through the month of June, is said to prevent the deposit of eggs on the plants.

Planting the onions in a new place as remote as possible from where they were grown the previous year has been found useful, as the flies are not supposed to migrate very far.

Pulverized gas lime scattered along between the rows has been useful in keeping the flies away.

Watering with liquid from pig pens collected in a tank provided for the purpose, was found by Miss Ormerod to be a better preventive than the gas lime.

When the onions have been attacked and show it by wilting and changing color, they should either be taken up with a trowel and burned, or else a little diluted carbolic acid, or kerosene oil, should be dropped on the infested plants to run down them and destroy the maggots in the roots and in the soil around them.

Instead of sowing onion seed in rows, they should be grown in hills, so that the maggots, which are footless, cannot make their way from one hill to another.THE CABBAGE BUTTERFLY.Pieris rapae (Linn.)

In the New England States there are three broods of this insect in a year, according to Mr. Scudder, the butterflies being on the wing in May, July, and September; but as the time of the emergence varies, we see them on the wing continuously through the season.

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