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Turbines
Turbines.
188
ing needle at right angles to the arms; and in both cases the given angles may be multiplied at pleasure; thus 40 ° and 50 ° may be taken as w'ell as 45% and the deflecting needle may be likewise fixed in the line of dip so as to repel the suspended needle from it, instead of using the weights alone for this purpose, and in this way the relation of the needles with respect to the earth's magnetism, may be ascertained by applying" the weights as described in the case of deflectors. It will not be requisite, at any time. to employ extremely minute weights; as the value of small difference in the angles may easily be estimated in weight.~; thus it'll, of a grain should cause the needle, under given circumstances, to pass through 30' ~ of a grain, will be represented by 3'. In all observations on the magnetic intensity, the temperature should be noted, and the needful corrections applied, the amount of" which may I ~ readily ascertained by experiments, such as covering the instrument with a heated vessel inverted~ or admitting heated air under it, &.e. In one instrument, a needle, when deflected by weights 50 ° from the dip, had the angle increased more than one minute, by every degree (Fah.) of augmented temperature: in other needles of weaker intensity, the influence of temperature has been less considerable; the ratio appears to be nearly uniform within the ordinary range of changes in this climate. I f the needles are tempered very hard throughout, and, after havingbeen magnetised, heated to 180 ° or 200 °, Mr. Fox has found that they sometimes retain their force without any appreciable change tbr a long period of time, although he has continually observed tl~at the magnetic axis ~ of a given needle, is liable to frequent variation, even without its having been retouched. This is shown by its having at one time uniformly an excess of dip, when facing east for instance, and at another, when facing west, and this without allotting the mean results on either occasion. He also finds that needles attain their maximum force after having been rubbed by a magnet or magnets two or three times only. AnnalsElectricity.
NOTICE~ )'r~oH THE :FRENCH JOURNALS, TRAb,~$LATEDFOR, THE JOURNALOr THE FaANKLIN ~INsTITUT~:, BY J. Gl4I$colff.
Turbines. M. Savary read a repnrt (to the Academy of Sciences, Paris,) in hisowa name, anti those of M. M. Prony, Arago and Gambey, on a memoir of M. Morin, containing the result of experiments on the turbines of M. Fourneyron. ~: Under the general name of turbines is understood water wheels which have scarcely any thing more in eomtnon than that of turning on a vertical axis. Thuse which an engineer, M. Bardin, invented and first made known under this appellation, receive the water at the top of a vertical cylinder or drum, and discharge it at the bottom. The water enters and issues near the circumference, and runs along spiral channels bent round the:~Sur~ face of the drum, which must be half as high as the whole disposable f~l! 0f the water. * This fact suggests the expediency of having the wide part of a h0dlii~ital vans tion needle vertical and not horizontal, to ensure the greatest degre¢i of~aaiformity in its indications. VOL, X X I I I . - - N o . ~.--FEnRtrARY 1839. 12
134
Progress of Physical Science.
I n the turbines of M. Fourneyron, the drum is never very thick, a foot or so, for example. The water rushes obliquely in horizontal jets round the contour of an internal vertical cylinder, and enters all the comport. ments of the wheel~ which, in its revolutions, just clears this cylinder, presses upon the curviliuear buckets which lie between the horizontal bases, and escapes horizontally by a vertical aperture in the exterior drum. W e may form an idea of the turbines of I~/I. 1' ourneyron by su ~posm_~ a common wheel with curved pallets to lie liar, and that the water, entering the pallets in the centre, issues at the circumference. M. Poneelet proposed, in 18~6, an arrangement the reverse of that now mentioned~the water entering at the circumference and passing oft" at the centre. It will be sufftcient to state, that the experiments of M. Mot'in on the turbines ofM. Fourneyron, lead to the conclusion that they are, at least~ as advantageous as the best wheels of the ordinary kiud;--in thct, under falls which varied fi'om the weak value of 1 toot to those of 1, ~, 5, and 7 or 8 yards, the disposable work of the turbines amounted to 7 or 8 tenths of the motive power. This is the effect absolute. With regard to the variable circumstances under which a hydraulic mover may be piaced for useful purposes~ the reporter states that the turbines present some special advantages. They are, he says, in reality, of all kindsofhydraulie wheels~ those whicl b under the least bulk, are available with the smallest quantity of water. The water which propels them does not press upon the axles. The immense velocities~ and the variable velocities which they are allowed to take without sacrificing any thing of their ettbct, admits, in mat~y factories, of the suppression of the wheet work and the heavy axles which are designed to transmit, with accelerated motitm~ the slow movement of the great bucket wheel. Another property of the turbines is still more imi~ortant. M. Morin~as well as other engineers, observes that they operate as well when immersed, (noycies) as when out of water. Perhaps it xvouhl be as well to admit, in such a case~ of a slight difference. At inure than the depth of a yard under water, the liquid sheet escapes from the buckets with as much facility as at the surface. The action depends only on the difference of level between the upper and lower part of the current, and not upon the absolute hei~ht of either. This is a most valuable property of the new wheels~ as it renders the entire fall of water available under all circumstances. L'Institut. •
,
4~
Salurn's Ring--~q 2~eu,S~,bdivision. I t is known that the ring of'S:~turn is comprised of two concentric rings separated by an empty space, which presents the appearance of a dark line, visible only by powerful glasses. Short imagined that he had seen a greater number of subdivisions in the riv.g, and some modern observers have confirmed this assertion. M. Encke made, last spring, some new observations on this celestial object with thegreat achromatic telescope of 9 inches aperture and 15 feet focal length, belonging to the Observatory of Berlin. The result he thus communicated to M. Schumaker. On the night of April ~Sth, 18S7, whichwas very clear, I tried, upon Saturn, a new achromatic ocular of the mechanician Duwe, of Berlin, with a power of 600, and a field of more than 6 minutes, in the whole extent of which the image had all the neatness that I could desire. Besides the eom-
188
ing needle at right angles to the arms; and in both cases the given angles may be multiplied at pleasure; thus 40 ° and 50 ° may be taken as w'ell as 45% and the deflecting needle may be likewise fixed in the line of dip so as to repel the suspended needle from it, instead of using the weights alone for this purpose, and in this way the relation of the needles with respect to the earth's magnetism, may be ascertained by applying" the weights as described in the case of deflectors. It will not be requisite, at any time. to employ extremely minute weights; as the value of small difference in the angles may easily be estimated in weight.~; thus it'll, of a grain should cause the needle, under given circumstances, to pass through 30' ~ of a grain, will be represented by 3'. In all observations on the magnetic intensity, the temperature should be noted, and the needful corrections applied, the amount of" which may I ~ readily ascertained by experiments, such as covering the instrument with a heated vessel inverted~ or admitting heated air under it, &.e. In one instrument, a needle, when deflected by weights 50 ° from the dip, had the angle increased more than one minute, by every degree (Fah.) of augmented temperature: in other needles of weaker intensity, the influence of temperature has been less considerable; the ratio appears to be nearly uniform within the ordinary range of changes in this climate. I f the needles are tempered very hard throughout, and, after havingbeen magnetised, heated to 180 ° or 200 °, Mr. Fox has found that they sometimes retain their force without any appreciable change tbr a long period of time, although he has continually observed tl~at the magnetic axis ~ of a given needle, is liable to frequent variation, even without its having been retouched. This is shown by its having at one time uniformly an excess of dip, when facing east for instance, and at another, when facing west, and this without allotting the mean results on either occasion. He also finds that needles attain their maximum force after having been rubbed by a magnet or magnets two or three times only. AnnalsElectricity.
NOTICE~ )'r~oH THE :FRENCH JOURNALS, TRAb,~$LATEDFOR, THE JOURNALOr THE FaANKLIN ~INsTITUT~:, BY J. Gl4I$colff.
Turbines. M. Savary read a repnrt (to the Academy of Sciences, Paris,) in hisowa name, anti those of M. M. Prony, Arago and Gambey, on a memoir of M. Morin, containing the result of experiments on the turbines of M. Fourneyron. ~: Under the general name of turbines is understood water wheels which have scarcely any thing more in eomtnon than that of turning on a vertical axis. Thuse which an engineer, M. Bardin, invented and first made known under this appellation, receive the water at the top of a vertical cylinder or drum, and discharge it at the bottom. The water enters and issues near the circumference, and runs along spiral channels bent round the:~Sur~ face of the drum, which must be half as high as the whole disposable f~l! 0f the water. * This fact suggests the expediency of having the wide part of a h0dlii~ital vans tion needle vertical and not horizontal, to ensure the greatest degre¢i of~aaiformity in its indications. VOL, X X I I I . - - N o . ~.--FEnRtrARY 1839. 12
134
Progress of Physical Science.
I n the turbines of M. Fourneyron, the drum is never very thick, a foot or so, for example. The water rushes obliquely in horizontal jets round the contour of an internal vertical cylinder, and enters all the comport. ments of the wheel~ which, in its revolutions, just clears this cylinder, presses upon the curviliuear buckets which lie between the horizontal bases, and escapes horizontally by a vertical aperture in the exterior drum. W e may form an idea of the turbines of I~/I. 1' ourneyron by su ~posm_~ a common wheel with curved pallets to lie liar, and that the water, entering the pallets in the centre, issues at the circumference. M. Poneelet proposed, in 18~6, an arrangement the reverse of that now mentioned~the water entering at the circumference and passing oft" at the centre. It will be sufftcient to state, that the experiments of M. Mot'in on the turbines ofM. Fourneyron, lead to the conclusion that they are, at least~ as advantageous as the best wheels of the ordinary kiud;--in thct, under falls which varied fi'om the weak value of 1 toot to those of 1, ~, 5, and 7 or 8 yards, the disposable work of the turbines amounted to 7 or 8 tenths of the motive power. This is the effect absolute. With regard to the variable circumstances under which a hydraulic mover may be piaced for useful purposes~ the reporter states that the turbines present some special advantages. They are, he says, in reality, of all kindsofhydraulie wheels~ those whicl b under the least bulk, are available with the smallest quantity of water. The water which propels them does not press upon the axles. The immense velocities~ and the variable velocities which they are allowed to take without sacrificing any thing of their ettbct, admits, in mat~y factories, of the suppression of the wheet work and the heavy axles which are designed to transmit, with accelerated motitm~ the slow movement of the great bucket wheel. Another property of the turbines is still more imi~ortant. M. Morin~as well as other engineers, observes that they operate as well when immersed, (noycies) as when out of water. Perhaps it xvouhl be as well to admit, in such a case~ of a slight difference. At inure than the depth of a yard under water, the liquid sheet escapes from the buckets with as much facility as at the surface. The action depends only on the difference of level between the upper and lower part of the current, and not upon the absolute hei~ht of either. This is a most valuable property of the new wheels~ as it renders the entire fall of water available under all circumstances. L'Institut. •
,
4~
Salurn's Ring--~q 2~eu,S~,bdivision. I t is known that the ring of'S:~turn is comprised of two concentric rings separated by an empty space, which presents the appearance of a dark line, visible only by powerful glasses. Short imagined that he had seen a greater number of subdivisions in the riv.g, and some modern observers have confirmed this assertion. M. Encke made, last spring, some new observations on this celestial object with thegreat achromatic telescope of 9 inches aperture and 15 feet focal length, belonging to the Observatory of Berlin. The result he thus communicated to M. Schumaker. On the night of April ~Sth, 18S7, whichwas very clear, I tried, upon Saturn, a new achromatic ocular of the mechanician Duwe, of Berlin, with a power of 600, and a field of more than 6 minutes, in the whole extent of which the image had all the neatness that I could desire. Besides the eom-