The balance-spring will likewise be acted on under similar circumstances; I should therefore think it absolutely necessary, that all the steel in the machine should be divested of the fixed magnetic qua lity; the variable ones will have no effect on each other: this can always be done by the action of fire, and if the mechanic, in the process of hardening and temper ing the steel, always carefully cools it in a direction at right angles with the dipping-needle, it will rarely be found to possess any pot tion of fixed magnetism, as, on the contrary, it will be found, that small steel bodies, if heated redhot, and cooled in the direction of the dipping-needle, will often re quire this quality. I am of opinion, that this fixed magnetism, if carefully excluded from the machine at first, will not be found to return from the continued motion of its parts. and that he attributes it to the same cause that I do, viz. a portion of fixed magnetism in the steel of the balance or its spring. For my part, I think it will not be found possible to ascertain any ship-rate for chronometers which shall correct the errors arising from this cause, from the direction and strength of the attraction of the iron in a ship undergoing such considerable changes as it does in different dips. I always considered the remedy to lie alone in the hands of the maker, who should carefully ascertain that no steel whatever in a chronometer possesses any fixed magnetic quality; and I pointed this out to a chronometer-maker in London in November 1820, shewing him, amongst a number of balances, those which had any portion of fixed magnetism, and those which had not, &c.; but it is requisite, that, in this respect, not only the balance and its spring should be attended to, but that all the steel in the instrument should be deprived of this quality, particularly the steel-spindles of the fusee, barrel, &c. for it is to magnetic attraction, residing wholly in the machine, that I attribute the alteration which takes place in the rates of chronometers on shore in different parts of the world, and which is often very considerable. These attractions may act in seveNew Chemical Combination.-M. ral ways. If there is fixed mag- Dobereiner, professor of Chemistry netism in the balance, and variable in the University of Jena, by magnetism in the spindles of the series of entirely new experiments, wheels, the rate may be altered by has ascertained that platina, the any considerable alteration in the heaviest of all elementary sub dip, as the direction and strength stances, when reduced into very of the variable magnetism will fine particles, produces by simple thereby become changed; the same contact with hydrogen gas, (the effect may be produced if the fixed lightest of elementary substances), magnetism is in the spindles of the A very necessary precaution with respect to the use of these instruments, is always to hang them up on board ship at a considerable distance from the compasses. I have known an excellent chronometet rendered useless for the time, by being kept within two feet of the cabin compass, and which, when removed to a different part of the cabin, performed remarkably well. an electrical or dynamic combina wheels, &c. and the variable mag- tion, which, if brought into contac netism in the steel of the balance. with hydrogen gas or with atmos pheric air, instantly dissolves itself yielding fire and water. To prove this important fact by a brilliant experiment, M. Dobereiner makes hydrogen pass from a reservoir, by a capillary tube, curved below, upon pure platina in powder, which is contained in a glass tunnel, hermetically sealed at the point, so that the gas mingles with the atmospheric air before it touches the platina. The moment that the current of gas reaches the surface of the platina, the power of that metal becomes red and burning, and this phenomenon continues as long as the stream of gas is directed upon it. New compound of Iodine. Iodide of Carbon ?-Messrs. Ferrari and Frisiani, whilst preparing the iodate and hydriodate of potassa, observed the production of a new compound of iodine. It may be obtained thus:-Heat an ounce of iodine, with a little water, on a sand bath, and add to it, by degrees, about two ounces of potash; when the two salts above mentioned will be formed. In order to saturate the excess of alkali, pour in, by degrees, a tincture composed of one ounce of iodine to six ounces of alcohol, specific gravity 837. When the re-action of the tincture on the potash is finished, pour the hot liquor on a filter, and the liquid which passes through will, as it cools, deposit yellow crystals, of the substance; they should be carefully washed in cold water, to remove all the iodate and hydriodate of potash. Another method is, to take the alcoholic solution of the two salts, prepared as above, and distil it: and when the fluid which comes over ceases to be coloured, to change the receiver; the colourless liquor then obtained, upon cooling, deposits very pure crystals, of the substance in question. If the distillation be suspended from time to time, and the retort allowed to cool, beautiful crystals of the substance form in it. If strong alcohol be used in the above operations, and but little water, then, upon adding water to the filtered liquor, the substance is precipitated in abundance. This substance is solid, of a lemon yellow colour, tastes like nitric ether, and has an odour like that of saffron. Its form is a compressed hexahedron (esaedro schiacciato). It is insoluble in water, alkalies, or acids, but soluble in alcohol and ether. It fuses and sublimes by a gentle heat, but at a higher tem perature becomes discoloured, is decomposed, and evolves vapours of iodine, leaving behind a mere trace of carbon.Giornale de Fisica, Vegetation in Atmospheres of different Densities.-The following experiments have been made by professor Dobereiner of Jena Two glass vessels were procured, each of the capacity of 320 cubic inches, two portions of barley were sown in portions of the same earth, and moistened in the same degree, and then placed one in each vessel. The air was now exhausted in one, till reduced to the pressure of 14 inches of mercury, and condensed in the other, until the pressure equalled 56 inches. Germination took place in both nearly at the same time, and the leaflets appeared of the same green tint; but at the end of 15 days the following differences existed. The shoots in the rarefied air were six inches in length, and from nine to ten inches in the condensed air. The first were expanded and soft; the last rolled round the stem and solid. The first were wet on their surface, and especially towards the ex tremities; the last were nearly dry. "I am disposed," says M. Dobereiner," to believe, that the diminution in the size of plants, as they rise into higher regions on mountains depends more on the diminution of pressure than of heat." Sugar for preserving Fish.Dr. McCulloch, of Edinburgh, has ascertained that the antiseptic quality of sugar is sufficient to preserve fish in the most excellent condition. He states, that this substance is so active, that fish may be preserved in a dry state, and perfectly fresh, by means of sugar alone, and even with a very small quantity of it. He has thus kept salmon, whitings, and cod, for an indefinite length of time; and by this simple means fresh fish may be kept in that state some days, so as to be as good when boiled as when just caught. It is added, that "if dried and kept free from mouldiness, there seems no limit to their preservation; and they are much better in this way than when salted. The sugar gives no disagreeable taste. This process is particularly valuable in making what is called kippered salmon: and the fish preserved in this manner are far superior in quality and flavour to those which are salted or smoked. If desired, as much salt may be used as to give the taste that may be required; but this substance does not conduce to their preserva tion. In the preparation, it is barely necessary to open the fish and to apply the sugar to the mus cular part, placing it in an horizontal position for two or three days, that this substance may penetrate After this it may be dried; and it is only further necessary to wipe and ventilate it occasionally, to prevent mouldiness. A table spoonful of brown sugar is suffici ent in this manner for a salmon of five or six pounds weight; and if salt is desired, a tea-spoonful or more may be added; saltpetre may be used instead, in the same proportion, if it is desired, to make the kipper hard.” AGRICULTURE AND BOTANY. On the destruction of Caterpillars on fruit trees. In May last I (Mr. Sweet, Bristol,) found the gooseberry caterpillar had begun its usual ravages on the leaves of a quarter of gooseberries in my nursery near Bristol. In the last and former season, among many other applications which had been tried, in vain, lime had been used, but in a dry state. I resolved this year to try the effect of it in a different way a bushel of stone lime was therefore slacked, and covered up for a few hours, to make it more soft and fine; it was then sifted through a mason's sieve of the finest kind, which made it almost an impalpable powder. A man with a light garden-engine was then directed to play water in dif ferent directions among the leaves, so that every part of the plants was wet; another man followed closely with a coal-box full of the fine lime-powder, scattering it with his hand, so as to cause it to appear like smoke, and to spread itself on 1 the under as well as the upper part of the leaves, so that not a single leaf was left untouched by it. In the course of the day I noticed, that, though some of the insects were still alive, they were much injured, and on the following day I could find none alive; some stragglers came on some time after wards, but they were so few, that I did not think it worth while to apply the lime a second time. After the application the trees recovered their natural colour, and grew with their usual vigour. A day should be chosen for the operation when little wind is stirring, but particularly when there is no rain: I think the absence of sun, or a cloudy day, preferable for the operation. The earlier the remedy is applied after the insect is discovered, the better; and if it should be necessary to use it a second time, it must be done before the fruit changes colour, lest it be disfigured by the application of the lime. The lime need not to be thrown on thick, but should be well divided with the hand in casting it, so that every part of each leaf be touched. In small gardens, where no engine is kept, a watering-pot or syringe may be used, so as to wet every part of the tree. Encouraged by my success on the gooseberry bushes, I tried the lime against the black leech-like insect, or maggot, which is so destructive to thorns, pear, and cherry-trees; and found that wherever the lime touched the animals, if they were wet it destroyed them. It being difficult water high standard trees, I took the opportunity very early in the morning before the dew was eva It is the larva of a dipterous insect, or two-winged fly. porated, to apply the powder; slacking the lime over-night to have it ready. The powder was tried after a shower of rain, but rain following, the operation did not answer: where, however, these insects can be got at, they are more easily destroyed than those which infest the gooseberry bushes. Pear-trees against walls are often injured by these leech-like insects, but they can be watered and limed without difficulty. I have tried lime water thrown by the garden-engine, the lime being just slacked in the water making it warm: this answered tolerably well, but it required more lime, and rendered both the trees and the earth of the borders on which it fell unsightly. A decoction of elder-leaves mixed with soft soap was also applied: this had the effect of destroying the insects but the preparation is more expensive, and the operation more troublesome, than that with lime-powder-Trans. Horti. Society. Utility of Sparrows.-Mr. Bradly shews that a pair of sparrows, during the time they have their young to feed, destroy, on an average, every week, 3,360 caterpillars. This calculation he founds upon actual observation. He discovered that the two parents carried to the nest forty caterpillars in an hour. He supposed the sparrows to enter the nest only during twelve hours each day, which would cause a consumption of 480 caterpillars. This sum gives 3,360 caterpillars extirpated weekly from a garden. But the utility of these birds is not limited to this circumstance alone, for they likewise feed their young with butterflies and other winged insects, each of which, if not destroyed in this manner, would be the parents of hundreds of caterpillars. Gooseberries. The list of cultivated gooseberries includes 47 different sorts of the red gooseberry, 35 of the yellow, 53 of the green, and 44 of the white; of these, the weights of the best specimens are given. The largest red is the Top Sawyer, which weighed 26 dwts. 17 grains; the largest yellow is the Nelson's Waves, 21 dwts. 6 grains; the largest green is the Ocean, 26 dwts. 11 grains; and largest white, the Smiling Beauty, 22 dwts. 18 grains. royal botanic garden of Glasgow, Succory as blanched salad.-A variety of this plant, improved by cultivation, is much employed in France. The young leaves are used in salad; and for procuring them, successive growings are kept up in gardens. When the plant is raised in fields, the outer leaves are plucked at different periods of summer and autumn, and given to milch cows, by which it is said they afford about a third more milk than when fed on common fodder, but it at first acquires a slightly sour taste: butter is also more easily obtained from it. At the approach of winter, the roots are dug up and laid in a cellar horizontally in alternate layers with sand or light soil, with their heads outtermost and uncovered. In this situation they are kept excluded from frost and also from light, during which they afford the blanched roots called Barbe de Capucin, used as winter salad. The roots are sometimes also put with sand into barrels having numerous holes in their sides, through which the shoots very easily push, and it is so tender that it requires are cut off when required. Bar- little cooking, and so easy of di rels thus prepared are sometimes gestion, that it is the common taken on board vessels about to practice in the country to give it sail, and afford fresh salad for many to convalescents and persons with weak stomachs, being thought of a New Esculent Plant.In the much less flatulent nature than months. to grow the |