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Magnetic gauge for steam boilers
210
.Mechanics, Physics, and Chemistry.
corners to diminish the risk of its slipping ; hut for very accurate work, such as engravers'~ this may be more effectually done by fixing the back of the rule to the drawing-table frame, or hoard with pros, reversing the clamp, D, and placing it to act on the other side of the stop-stud, and working the front hall' of tile rule by the screw alone. This arrangement will allow a tool to be pressed against the straight-edge with suiIicient force for engraving wood blocks or steel plates. One or two other things remain to be noticed "~'hieh apply to ordinary rules as well as to those above described. First, they should have disks of thin metal between ttle joint arms and the rule, to prevent any rubbing at a distance from tile rivets. Secondly, the straight-edge should be of steel, hardened and tempered to resist the action of tools drawn along it ; the steel, which is cheaply prepared for ladies' stays, answers very well; it may be fixed by being cemented into a groove in the rule. Thirdly, the rule, instead of being flat on the under side, as they are usually made, should be slightly bevelled towards both edges, so as to divide the width into three equal bearings ; this effects two objects, one of which is to make the rule easier to work and less liable to shift accidentally, as when one side is pressed down it raises the other, and keeps it quite free whilst it is being moved ; the oflwr object is to enable the same straight-edge to be raised different distances from the paper whilst drawing the lines by pressing down the front, middle~ or back of the rule. As several years have elapsed since the construction was completed and arranged in the present form, after several others that occurred to me had been tried, and as improvements in mathematical instruments very seldom repay tile heavy cost of a patent, the construction is now open for any one to manuf.mture; but in order to afford further facility for its being properly carried out, [ have furnished detailed instruetimls to the principal mmhemafieal instrument ,nakers, who are making arrangements for supplying fl~e improved rules to the p(~blic ; having done thus much in the matter and occupied several months with the rule at different times, it must rest with fllem whether it is perfectly manufactured or not.
.Magnetic Gau~e for Sleam Boilers.* This is said to be the first application of magnelism to steam-boilers. 'lhe apparatus consists of a melallic hollow spheriod suspended by an iron rod, the end of which is a bar of steel strongly magnetised. This magnet rises and falls in a brass box, which serves as a sort of cage to enclose it. Upon the face of this box, which is graduated in centimetres or inches, moves a small needle or pointer, separated from all mechanical support, hut attracted only through tile loop of the magnet, all of whose me,lions it foll~)ws. The extreme limits of the floating ball can only be reached by tou,:hing the slops which open the alarm-whistle~ so that a failure or an over-supldy of water is immediately detected. The graduated surface of' lhe g+mge is silvered, so that tile continual motion of the pointer is readily seen at any distance. # From the London Artizan, February, 1856.
On the Descent of Glaciers.
211
The apparatus is protected by a glass eover, which preserves the needle from injury and keeps the graduated scale eonstantly clean. The price of the gauge, withoat the valve, is from 170 to 180 francs, and the gauge and whistle fl'om 30 to 90 francs extra. This gauge is merely a bad copy of Faber's Magnetic Gauge, patented in this country, and described in this 3burnal, (present Series,)VoI. xxi, p. 215. The Faber Gaugo is very superior to the one exhibited at the French Exhibition, which has been altered merely to disguise the theft, and has no novelty but its defects. Emroa.
0~ the Descent of Gbzclers. By the Rev. Hst~Y M'OSELEY, M.A, F.R.S.* If we conceive two bodies of' the same form and dimensions (cubes for instance,) and of the same material, to be placed upon a uniform horizontal plane, and connected by a substance which alternately extends and contracts itself, as does a metallic rod when subjected to variations of temperature, it is evident that by the extension.of the intervening rod, each will be made to recede from the other by the same distance, and, by its contraction, to approach it by the same distance. But if they be placed o,t an inclined plane (one being lower than the other), then when by the increased temperature of the rod its tendency to extend becomes sufficient to push the lower of' the two bodies downwards, it will not have become suilicient to push the higher upwards. The effect of its extension will therefore be to cause the lower of the two bodies to descend whilst the h'gner remains at re,>t. The converse of this will result from eontra,'tion; for when the cont,'ac!ile force becomes sufficient to pull the upper body down the plane it will not have become sufficient to pull the lower up it. Thus, in the contraction of the substance which intervenes between the two bodies, the lower will remain at rest whilst the upper desee.nds. As often, then, as the expansion and contraction is repeated the two bodies will descend the plane until, step by step, they reach the bottom. Fig. I. Suppose the uniform bat" AB placed on an inclined phme, and subject to extension fi'om increase of temperature, a portiou xs will descend, and the re,t xA will ascend; the point x where lhey separ,ae being determined by the condition that Ilia fmee reqtfisite to push xa up the plane is equal to that required to push xt~ down it. Let ax--=--:c, AS=L, weight of each linear unit--tt, /=inclination of plane, ¢,= limiting angle of resista,ee, .-. u.7==weight of Ax, u (1.--z)---weight of' ,~x. Now, the f(~ree aetinff p,lralh.I to ~rl inclined plane which is necessary to push a weight w up it, is rcprcsented by sin (~1-i) . •
From the Lond., Edin., and Dub. Philos. Meg., July, I$5,~.
.Mechanics, Physics, and Chemistry.
corners to diminish the risk of its slipping ; hut for very accurate work, such as engravers'~ this may be more effectually done by fixing the back of the rule to the drawing-table frame, or hoard with pros, reversing the clamp, D, and placing it to act on the other side of the stop-stud, and working the front hall' of tile rule by the screw alone. This arrangement will allow a tool to be pressed against the straight-edge with suiIicient force for engraving wood blocks or steel plates. One or two other things remain to be noticed "~'hieh apply to ordinary rules as well as to those above described. First, they should have disks of thin metal between ttle joint arms and the rule, to prevent any rubbing at a distance from tile rivets. Secondly, the straight-edge should be of steel, hardened and tempered to resist the action of tools drawn along it ; the steel, which is cheaply prepared for ladies' stays, answers very well; it may be fixed by being cemented into a groove in the rule. Thirdly, the rule, instead of being flat on the under side, as they are usually made, should be slightly bevelled towards both edges, so as to divide the width into three equal bearings ; this effects two objects, one of which is to make the rule easier to work and less liable to shift accidentally, as when one side is pressed down it raises the other, and keeps it quite free whilst it is being moved ; the oflwr object is to enable the same straight-edge to be raised different distances from the paper whilst drawing the lines by pressing down the front, middle~ or back of the rule. As several years have elapsed since the construction was completed and arranged in the present form, after several others that occurred to me had been tried, and as improvements in mathematical instruments very seldom repay tile heavy cost of a patent, the construction is now open for any one to manuf.mture; but in order to afford further facility for its being properly carried out, [ have furnished detailed instruetimls to the principal mmhemafieal instrument ,nakers, who are making arrangements for supplying fl~e improved rules to the p(~blic ; having done thus much in the matter and occupied several months with the rule at different times, it must rest with fllem whether it is perfectly manufactured or not.
.Magnetic Gau~e for Sleam Boilers.* This is said to be the first application of magnelism to steam-boilers. 'lhe apparatus consists of a melallic hollow spheriod suspended by an iron rod, the end of which is a bar of steel strongly magnetised. This magnet rises and falls in a brass box, which serves as a sort of cage to enclose it. Upon the face of this box, which is graduated in centimetres or inches, moves a small needle or pointer, separated from all mechanical support, hut attracted only through tile loop of the magnet, all of whose me,lions it foll~)ws. The extreme limits of the floating ball can only be reached by tou,:hing the slops which open the alarm-whistle~ so that a failure or an over-supldy of water is immediately detected. The graduated surface of' lhe g+mge is silvered, so that tile continual motion of the pointer is readily seen at any distance. # From the London Artizan, February, 1856.
On the Descent of Glaciers.
211
The apparatus is protected by a glass eover, which preserves the needle from injury and keeps the graduated scale eonstantly clean. The price of the gauge, withoat the valve, is from 170 to 180 francs, and the gauge and whistle fl'om 30 to 90 francs extra. This gauge is merely a bad copy of Faber's Magnetic Gauge, patented in this country, and described in this 3burnal, (present Series,)VoI. xxi, p. 215. The Faber Gaugo is very superior to the one exhibited at the French Exhibition, which has been altered merely to disguise the theft, and has no novelty but its defects. Emroa.
0~ the Descent of Gbzclers. By the Rev. Hst~Y M'OSELEY, M.A, F.R.S.* If we conceive two bodies of' the same form and dimensions (cubes for instance,) and of the same material, to be placed upon a uniform horizontal plane, and connected by a substance which alternately extends and contracts itself, as does a metallic rod when subjected to variations of temperature, it is evident that by the extension.of the intervening rod, each will be made to recede from the other by the same distance, and, by its contraction, to approach it by the same distance. But if they be placed o,t an inclined plane (one being lower than the other), then when by the increased temperature of the rod its tendency to extend becomes sufficient to push the lower of' the two bodies downwards, it will not have become suilicient to push the higher upwards. The effect of its extension will therefore be to cause the lower of the two bodies to descend whilst the h'gner remains at re,>t. The converse of this will result from eontra,'tion; for when the cont,'ac!ile force becomes sufficient to pull the upper body down the plane it will not have become sufficient to pull the lower up it. Thus, in the contraction of the substance which intervenes between the two bodies, the lower will remain at rest whilst the upper desee.nds. As often, then, as the expansion and contraction is repeated the two bodies will descend the plane until, step by step, they reach the bottom. Fig. I. Suppose the uniform bat" AB placed on an inclined phme, and subject to extension fi'om increase of temperature, a portiou xs will descend, and the re,t xA will ascend; the point x where lhey separ,ae being determined by the condition that Ilia fmee reqtfisite to push xa up the plane is equal to that required to push xt~ down it. Let ax--=--:c, AS=L, weight of each linear unit--tt, /=inclination of plane, ¢,= limiting angle of resista,ee, .-. u.7==weight of Ax, u (1.--z)---weight of' ,~x. Now, the f(~ree aetinff p,lralh.I to ~rl inclined plane which is necessary to push a weight w up it, is rcprcsented by sin (~1-i) . •
From the Lond., Edin., and Dub. Philos. Meg., July, I$5,~.