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ROYAL INSTITUTION.
672
zine precipitating wire, blow-pipe, charcoal, express universally the fact, that the cond platina foil, Lerzelius’ reduction tube, test- tion of one body is electrically changed by the approximation of another excited body. tube, green glass tube, glass rod, watch- Thus, a glass tube being rubbed by a waxed glass, bent tube, litmus and turmeric paper cloth, and in this manner excited, when copper wire. The tests are contained in nte placed in the neighbourhood of a cylinder stoppered bottles, holding chloride of tin; of brass or other metal, puts the cylinder nitr. ox. of silver; nitr. ox. of barium; car- into a state in which it exhibits electrical bonate of potassa ; hydrosulphate of ammo- phenomena, such as attraction and repulsion of light bodies. This is an example of nia ; chloride of calcium ; pure potassa; and Dr. Faraday refers all the induction, persulphate of iron ; iodide potassium ; phenomena which have hitherto been exferrocyanide of potassium. Three small pill- pressed by the words conduction, insulation, boxes contain;sulphate of copper, sulphuret &c., to this single principle. The lecturer exhibited, with his wonted of iron, and chromate of potassa. The and precision, a number of experielegance mineral omitted from the acids are strong in illustration of the nature of the ments, case, to prevent the effect of accidental inductive process. Thus, a cylinder of glass
breakage.
excited in the ordinary manner, being ap’Ve have said enough to show that every proximated to two insulated metallic cylinmedical man ’who may be called upon to ders, formed like common conductors, an electric condition was induced in the metalattend a coroner’s inquest, may usefully lic cylinders, and each of them exhibited possess himself of so convenient an appa- the same electric phenomena after the glass ratus. cylinder was removed. But if the most distant of the metallic cylinders were removed before the glass rod, then the two were found to be in difl’erent states of electricity, the one being positive, and the other ROYAL INSTITUTION. negative. Having also induced a negative state of electricity in surrounding matter, Friday, Jan. 19, 1838. by charging a large electric battery through PROFESSOR FARADAY ON ELECTRIC INDUCTION. the medium of a powerful machine, he exTnis was the first evening meeting of the hibited the force and activity with which members for the season, and exhibited a the electric fluid rushes to an equilibrium 11 grand re-union" of scientific men. Dr. through the medium of a small iron chain Faraday having made a series of experi- suspended in festoons. In this experiment ments to ascertain the true laws of induc- two kinds of light were made evident; a tion before the Royal Society, the results of blue light, produced by the transit of the which are now in course of publication by electric fluid from link to link; and a white that learned body, repeated this evening light, the effect of a combustion of the iron; several of the series, and presented them as the blue being the index of a series of ina bonne bouche to the scientific gourmands ductions. who patronise Faraday’s exquisite cuisine. The lecturer did not exhibit any direct No science, according to the lecturer, experiment to prove the successive polarisahas ever made so rapid a progress as elec- tion of the atoms intervening between the tricity, and none has been so much re- negative and positive bodies, alleging that tarded by the assumption of hypotheses, the experiments corroborative of his princiwhich the world at large have received with ples in this respect, and which are detailed the most complacent gullibility. It was in the forthcoming volume of the " Philosostated, as an indisputable principle, by phical Transactions," were too delicate to (Epimus, and admitted by Cavendish and be satisfactorily demonstrated in the prePauillet, " that the action of electricity is sence of a large audience ; but he made an in right lines, and with a force inversely as illustrative experiment in this ingenious the square of the distance," like common way : Having placed three small bars of forces : and that air, glass, or other inter- soft iron upon pivots in a line, they were posing substances, act as impediments to its seen to revolve horizontally ad libitum, but transmission. Faraday controverts this theory when a magnet was placed at one end of altogether, and labours by his experiments the series, the three bars became succesto prove, that electric induction is not pro- sively polarised, and became so arranged duced by a force acting in right lines, but that the positive pole of one was in contact in curved or angular lines as well; and that with the negative pole of the other. When it is not transmitted through empty space, the middle bar is removed, however, the first but can alone be communicated from one bar alone is affected hy the magnet, the body to another by the successive polarisa- third remaining perfectly indifferent. This tion of contiguous molecules. was a kind of metaphorical experiment, to Dr. Faraday uses the term induction to show the mode in which, according to Fara.
673
day, the electric fluid travelled from particle from the perpendicular, when the mirror is particle of matter. rapidly revolved, produces, by reflection The final experiment of the lecturer, des- on the face of the glass, an illuminated cirtined to prove that the electric matter did cular line of equal breadth throughout. But, not act in right lines only, was the follow- if the flame of hydrogen be substituted for ing :-Having excited a cylinder of shell- that of the taper, the illuminated circle will lac, he placed it on an insulated pedestal, be of unequal breadth, alternately widening and by means of an insulated brass ball, and narrowing at regular intervals. This exhibited its character on a paper ball sus- appearance according to Professor Wheatpended by a glass thread. He then placed stone, is owing to the alternate enlargement a disk of brass upon the top of the shell-lac and diminution of the flame, by which means column, and having momentarily touched a vacillating light, and varying degrees of the disk, to render it indifferent, he placed temperature are produced, the former acthe insulated brass ball upon the centre counting for the varying dimensions of the of the disk, and having thus obtained a luminous circle; and the latter, through the portion of excitement, showed by approxi- alternating contraction and expansion of the mating it to the paper ball, that it was air exciting the vibrations which engender charged by the same kind of electricity as the sound. when it derived its excitement directly Another unique fact relating to the origin from the shell-lac ; thus demonstrating that of sound-the production of vibration by the
to
the
electricity had passed from the shell-lac cylinder over the edges of the brass disk, and affording an example of what the lecturer termed «
contact of a hot with a cold metal, which has puzzled the natural philosophers for some years, Professor Forbes has attempted to explain in the following manner :-A piece of copper or brass, formed in the shape of a plaster spatula, having one surface like a double inclined plane, when heated and placed with the convex side downwards, resting on a flat ingot of lead, will assume a rapid and rocking motion, attended with a humming sound. The spatula, resting on its
induction round a corner." At the conclusion Mr. Faraday congratulated the members upon the improved appearance of the mansion, a handsome Corinthian colonnade having been erected on its front. He also alluded to a vulgar error, which was going the round of the news" that salt was a desirable means papers. of removing ice from the pavement." This crest, rapidly see-saws from side to side, the he thought a most dangerous plan, by which hot surface of the copper being apparently dry ice of the temperature of 32 degrees, repelled as soon as it has touched the lead on Hitherto this phenomenon has was converted into water at zero, a footing either side. not at all agreeable in his opinion. been explained by the supposition that the In the library we observed a print of the lead, being expanded by the approach of the celebrated German physiologist, Muller, hot copper, was thereby elevated, and repelled published by A. Schloss. He appears to be the copper, which, meeting with the same a young man, having " a fair large front opposition on its other phase, was thus aland eye sublime," with features denoting ternately repelled from side to side. Professor Forbes, not thinking this rationale strength of will. satisfactory, has instituted several experiJanuary, 15, 1838. ments, in order, if possible, to elicit the truth. There is no obvious expansion on MR. ADDAMS ON ACOUSTICS. the surface of the lead, but it must be conhere acThe season has commenced very tively, three concurrent courses of lectures siderable to throw back the copper to the on different branches of physics having been opposite side,-and he has, after some deliestablished. Mr. Addams having been apcome to the conclusion that the beration, pointed to deliver a series of prelections on phenomenon in question is due to the repellent He defined sound to be" a sensation excited power of caloric. in the mind by the vibrations of certain Having shown by experiment that musical bodies, conveyed to the sensorium through sounds produce vibrations in membranes, the medium of the auditory apparatus." and adduced this fact as a proof of the modits He noticed the only apparent exception is in which which the tne membrana tympani is the rule that sound is the result of vibra- operandi in a disMr. Addams affected gave by sound, tions," viz., the production of sound by the introduction of a flame of hydrogen gas into tinct but general description of the organa glass cylinder. This phenomenon has isation of the ear. He then illustrated, in a been proved by Professor Wheatstone to be pleasing manner, the mode in which sound the result of vibrations excited in the conducted through various bodies, and conis tained air, in the following experiment. produced the following table of the velocity
acoustics, commenced operations this day.
to operandi
The flameof an ordinary taperhorizontal being placed before mirror fixed a
on an
but with its surface inclined
a
,
axis, with which sound travels few degrees media.
through certain
674
by the formula of Newton, the rectilinear space occupied by the molecules which, if a cubic inch of water be converted into a cubic inch of steam, will be one-twelfth of the distance. By comparative experiments with a tuning fork, held over a tube closed at one end, and containing at one time air and at another time steam, and also by similar Of the woods, deal or cedar is the best trials with organ-pipes of various lengths, conductor, and consequently most fitted for Dr. Ritchie found a close agreement between musical instruments or stethoscopes. his theory and observation. He also proved . The influence of temperature in accele- that this theory furnishes the means of derating the transmission of sound, was exem- termining a priori the density of a liquid, if plified by two organ-pipes of the same pitch, the velocity of sound in the vapour of that the mere application of the hand to one rais- liquid be given. ing its pitch by a couple of notes. Mr. Addams appears satisfied with the January 26, 1838. calculations of Laplace in relation to the POISONOUS CANDLES.—GOOD EFFECTS OF PUBdiscrepancy between the theory of the LISHING ABUSES. velocity of sound through the atmosphere, Mr. BRANDE delivered a lecture this even. adopted by Sir Isaac Newton, and the results of experiment, and appears to attach ing on fatty matter and the manufacture of candles. A few weeks since we gave a no weight to the objections of Dr. Ritchie. The ordinary vehicle of sound is the at- full report of a lecture on fatty matter, delimosphere. Aristotle, deriving his informa- vered before the Westminster Medical Sotion from the Pythagorean school, acquired ciety by Mr. Everitt. That lecture emtolerably just notions of the nature of braced the chief topics which were dwelt sound. Galileo also was well acquainted upon by Mr. Brande. In mentioning the with harmonics. theoretically and Dracti- subject of arsenical candles, Mr. Brande of the service rendered to the public cally ; but it was reserved for Newton to sketch out the true theory of sound. In his by the Westminster Medical Society, from "Principia" he explained the origin of their investigation of the matter. In the aerial pulses, and by a fine, application of commencement of the use of arsenic in steadynamics he succeeded in calculating the rine candles, the quantity used was exceedcelerity of its transmission. He determined ingly small, not more than a tenth of a from theory that the velocity of the undulain a single candle. When he remon. tions of an elastic medium generally is equal grain strated at the time with a manufacturer on to that which a heavy body acquires in fallof using so poisonous a material, the danger of ing by the action gravity, through half the height of a homogeneous atmosphere of he was told, the doctors used small quanof arsenic as a tonic, and the candlethat ’medium ;but the actual velocity of soundj in atmospheric air is found to be one makers had only adopted a new method of eighth greater than what is assigned by that the stomach by the vapour of formula. This difference was attempted to strengthening that mineral. The candle-manufacturers. be accounted for by Newton, on the suppo-
spoke
tities
sition that the molecules of air are solid however, soon increased the quantity of the spheres, and that sound is transmitted arsenic, until it reached three, and even through them instanter. Laplace endea- four, grains in a single candle. Regarding voured to reconcile the difference between the statement which had been made, that theory and observation. by the hypothesis some manufacturers used one pound of that heat is disengaged from each successive to twenty-eight pounds of stearine, portion of air during the progress of the arsenic condensed wave. The late estimable Dr. he thought this must be erroneous, for he Ritchie regarded the hypothesis of Laplace he had found that a candle manufactured of as a gratuitous assumption, the falsehood of such proportions would not burn. From which is apparent from the fact that a rare- the exertions of the Society above alluded fied wave advances through air with the and the publicity given to their proceedsame velocity as a condensed wave, which to, the if in either instance would not be the case ings by press, he was happy to say that their progress were influenced by the heat he believed that at present there was not evolved. Dr. Ritchie has entered into cal- a single candle-manufacturer who used culations, to show, that if the molecules of arsenic ; it had been ascertained that a water be assumed as incompressible, and when at the temperature of maximum small quantity of magnesia, or fresh chalk density, very nearly in absolute contact, acted similarly on the stearine, and to these we ought, in estimating the velocity of less injurious substances the tallow-chan.. 3ound in steam to add to the velocity given dlers now resorted.
zine precipitating wire, blow-pipe, charcoal, express universally the fact, that the cond platina foil, Lerzelius’ reduction tube, test- tion of one body is electrically changed by the approximation of another excited body. tube, green glass tube, glass rod, watch- Thus, a glass tube being rubbed by a waxed glass, bent tube, litmus and turmeric paper cloth, and in this manner excited, when copper wire. The tests are contained in nte placed in the neighbourhood of a cylinder stoppered bottles, holding chloride of tin; of brass or other metal, puts the cylinder nitr. ox. of silver; nitr. ox. of barium; car- into a state in which it exhibits electrical bonate of potassa ; hydrosulphate of ammo- phenomena, such as attraction and repulsion of light bodies. This is an example of nia ; chloride of calcium ; pure potassa; and Dr. Faraday refers all the induction, persulphate of iron ; iodide potassium ; phenomena which have hitherto been exferrocyanide of potassium. Three small pill- pressed by the words conduction, insulation, boxes contain;sulphate of copper, sulphuret &c., to this single principle. The lecturer exhibited, with his wonted of iron, and chromate of potassa. The and precision, a number of experielegance mineral omitted from the acids are strong in illustration of the nature of the ments, case, to prevent the effect of accidental inductive process. Thus, a cylinder of glass
breakage.
excited in the ordinary manner, being ap’Ve have said enough to show that every proximated to two insulated metallic cylinmedical man ’who may be called upon to ders, formed like common conductors, an electric condition was induced in the metalattend a coroner’s inquest, may usefully lic cylinders, and each of them exhibited possess himself of so convenient an appa- the same electric phenomena after the glass ratus. cylinder was removed. But if the most distant of the metallic cylinders were removed before the glass rod, then the two were found to be in difl’erent states of electricity, the one being positive, and the other ROYAL INSTITUTION. negative. Having also induced a negative state of electricity in surrounding matter, Friday, Jan. 19, 1838. by charging a large electric battery through PROFESSOR FARADAY ON ELECTRIC INDUCTION. the medium of a powerful machine, he exTnis was the first evening meeting of the hibited the force and activity with which members for the season, and exhibited a the electric fluid rushes to an equilibrium 11 grand re-union" of scientific men. Dr. through the medium of a small iron chain Faraday having made a series of experi- suspended in festoons. In this experiment ments to ascertain the true laws of induc- two kinds of light were made evident; a tion before the Royal Society, the results of blue light, produced by the transit of the which are now in course of publication by electric fluid from link to link; and a white that learned body, repeated this evening light, the effect of a combustion of the iron; several of the series, and presented them as the blue being the index of a series of ina bonne bouche to the scientific gourmands ductions. who patronise Faraday’s exquisite cuisine. The lecturer did not exhibit any direct No science, according to the lecturer, experiment to prove the successive polarisahas ever made so rapid a progress as elec- tion of the atoms intervening between the tricity, and none has been so much re- negative and positive bodies, alleging that tarded by the assumption of hypotheses, the experiments corroborative of his princiwhich the world at large have received with ples in this respect, and which are detailed the most complacent gullibility. It was in the forthcoming volume of the " Philosostated, as an indisputable principle, by phical Transactions," were too delicate to (Epimus, and admitted by Cavendish and be satisfactorily demonstrated in the prePauillet, " that the action of electricity is sence of a large audience ; but he made an in right lines, and with a force inversely as illustrative experiment in this ingenious the square of the distance," like common way : Having placed three small bars of forces : and that air, glass, or other inter- soft iron upon pivots in a line, they were posing substances, act as impediments to its seen to revolve horizontally ad libitum, but transmission. Faraday controverts this theory when a magnet was placed at one end of altogether, and labours by his experiments the series, the three bars became succesto prove, that electric induction is not pro- sively polarised, and became so arranged duced by a force acting in right lines, but that the positive pole of one was in contact in curved or angular lines as well; and that with the negative pole of the other. When it is not transmitted through empty space, the middle bar is removed, however, the first but can alone be communicated from one bar alone is affected hy the magnet, the body to another by the successive polarisa- third remaining perfectly indifferent. This tion of contiguous molecules. was a kind of metaphorical experiment, to Dr. Faraday uses the term induction to show the mode in which, according to Fara.
673
day, the electric fluid travelled from particle from the perpendicular, when the mirror is particle of matter. rapidly revolved, produces, by reflection The final experiment of the lecturer, des- on the face of the glass, an illuminated cirtined to prove that the electric matter did cular line of equal breadth throughout. But, not act in right lines only, was the follow- if the flame of hydrogen be substituted for ing :-Having excited a cylinder of shell- that of the taper, the illuminated circle will lac, he placed it on an insulated pedestal, be of unequal breadth, alternately widening and by means of an insulated brass ball, and narrowing at regular intervals. This exhibited its character on a paper ball sus- appearance according to Professor Wheatpended by a glass thread. He then placed stone, is owing to the alternate enlargement a disk of brass upon the top of the shell-lac and diminution of the flame, by which means column, and having momentarily touched a vacillating light, and varying degrees of the disk, to render it indifferent, he placed temperature are produced, the former acthe insulated brass ball upon the centre counting for the varying dimensions of the of the disk, and having thus obtained a luminous circle; and the latter, through the portion of excitement, showed by approxi- alternating contraction and expansion of the mating it to the paper ball, that it was air exciting the vibrations which engender charged by the same kind of electricity as the sound. when it derived its excitement directly Another unique fact relating to the origin from the shell-lac ; thus demonstrating that of sound-the production of vibration by the
to
the
electricity had passed from the shell-lac cylinder over the edges of the brass disk, and affording an example of what the lecturer termed «
contact of a hot with a cold metal, which has puzzled the natural philosophers for some years, Professor Forbes has attempted to explain in the following manner :-A piece of copper or brass, formed in the shape of a plaster spatula, having one surface like a double inclined plane, when heated and placed with the convex side downwards, resting on a flat ingot of lead, will assume a rapid and rocking motion, attended with a humming sound. The spatula, resting on its
induction round a corner." At the conclusion Mr. Faraday congratulated the members upon the improved appearance of the mansion, a handsome Corinthian colonnade having been erected on its front. He also alluded to a vulgar error, which was going the round of the news" that salt was a desirable means papers. of removing ice from the pavement." This crest, rapidly see-saws from side to side, the he thought a most dangerous plan, by which hot surface of the copper being apparently dry ice of the temperature of 32 degrees, repelled as soon as it has touched the lead on Hitherto this phenomenon has was converted into water at zero, a footing either side. not at all agreeable in his opinion. been explained by the supposition that the In the library we observed a print of the lead, being expanded by the approach of the celebrated German physiologist, Muller, hot copper, was thereby elevated, and repelled published by A. Schloss. He appears to be the copper, which, meeting with the same a young man, having " a fair large front opposition on its other phase, was thus aland eye sublime," with features denoting ternately repelled from side to side. Professor Forbes, not thinking this rationale strength of will. satisfactory, has instituted several experiJanuary, 15, 1838. ments, in order, if possible, to elicit the truth. There is no obvious expansion on MR. ADDAMS ON ACOUSTICS. the surface of the lead, but it must be conhere acThe season has commenced very tively, three concurrent courses of lectures siderable to throw back the copper to the on different branches of physics having been opposite side,-and he has, after some deliestablished. Mr. Addams having been apcome to the conclusion that the beration, pointed to deliver a series of prelections on phenomenon in question is due to the repellent He defined sound to be" a sensation excited power of caloric. in the mind by the vibrations of certain Having shown by experiment that musical bodies, conveyed to the sensorium through sounds produce vibrations in membranes, the medium of the auditory apparatus." and adduced this fact as a proof of the modits He noticed the only apparent exception is in which which the tne membrana tympani is the rule that sound is the result of vibra- operandi in a disMr. Addams affected gave by sound, tions," viz., the production of sound by the introduction of a flame of hydrogen gas into tinct but general description of the organa glass cylinder. This phenomenon has isation of the ear. He then illustrated, in a been proved by Professor Wheatstone to be pleasing manner, the mode in which sound the result of vibrations excited in the conducted through various bodies, and conis tained air, in the following experiment. produced the following table of the velocity
acoustics, commenced operations this day.
to operandi
The flameof an ordinary taperhorizontal being placed before mirror fixed a
on an
but with its surface inclined
a
,
axis, with which sound travels few degrees media.
through certain
674
by the formula of Newton, the rectilinear space occupied by the molecules which, if a cubic inch of water be converted into a cubic inch of steam, will be one-twelfth of the distance. By comparative experiments with a tuning fork, held over a tube closed at one end, and containing at one time air and at another time steam, and also by similar Of the woods, deal or cedar is the best trials with organ-pipes of various lengths, conductor, and consequently most fitted for Dr. Ritchie found a close agreement between musical instruments or stethoscopes. his theory and observation. He also proved . The influence of temperature in accele- that this theory furnishes the means of derating the transmission of sound, was exem- termining a priori the density of a liquid, if plified by two organ-pipes of the same pitch, the velocity of sound in the vapour of that the mere application of the hand to one rais- liquid be given. ing its pitch by a couple of notes. Mr. Addams appears satisfied with the January 26, 1838. calculations of Laplace in relation to the POISONOUS CANDLES.—GOOD EFFECTS OF PUBdiscrepancy between the theory of the LISHING ABUSES. velocity of sound through the atmosphere, Mr. BRANDE delivered a lecture this even. adopted by Sir Isaac Newton, and the results of experiment, and appears to attach ing on fatty matter and the manufacture of candles. A few weeks since we gave a no weight to the objections of Dr. Ritchie. The ordinary vehicle of sound is the at- full report of a lecture on fatty matter, delimosphere. Aristotle, deriving his informa- vered before the Westminster Medical Sotion from the Pythagorean school, acquired ciety by Mr. Everitt. That lecture emtolerably just notions of the nature of braced the chief topics which were dwelt sound. Galileo also was well acquainted upon by Mr. Brande. In mentioning the with harmonics. theoretically and Dracti- subject of arsenical candles, Mr. Brande of the service rendered to the public cally ; but it was reserved for Newton to sketch out the true theory of sound. In his by the Westminster Medical Society, from "Principia" he explained the origin of their investigation of the matter. In the aerial pulses, and by a fine, application of commencement of the use of arsenic in steadynamics he succeeded in calculating the rine candles, the quantity used was exceedcelerity of its transmission. He determined ingly small, not more than a tenth of a from theory that the velocity of the undulain a single candle. When he remon. tions of an elastic medium generally is equal grain strated at the time with a manufacturer on to that which a heavy body acquires in fallof using so poisonous a material, the danger of ing by the action gravity, through half the height of a homogeneous atmosphere of he was told, the doctors used small quanof arsenic as a tonic, and the candlethat ’medium ;but the actual velocity of soundj in atmospheric air is found to be one makers had only adopted a new method of eighth greater than what is assigned by that the stomach by the vapour of formula. This difference was attempted to strengthening that mineral. The candle-manufacturers. be accounted for by Newton, on the suppo-
spoke
tities
sition that the molecules of air are solid however, soon increased the quantity of the spheres, and that sound is transmitted arsenic, until it reached three, and even through them instanter. Laplace endea- four, grains in a single candle. Regarding voured to reconcile the difference between the statement which had been made, that theory and observation. by the hypothesis some manufacturers used one pound of that heat is disengaged from each successive to twenty-eight pounds of stearine, portion of air during the progress of the arsenic condensed wave. The late estimable Dr. he thought this must be erroneous, for he Ritchie regarded the hypothesis of Laplace he had found that a candle manufactured of as a gratuitous assumption, the falsehood of such proportions would not burn. From which is apparent from the fact that a rare- the exertions of the Society above alluded fied wave advances through air with the and the publicity given to their proceedsame velocity as a condensed wave, which to, the if in either instance would not be the case ings by press, he was happy to say that their progress were influenced by the heat he believed that at present there was not evolved. Dr. Ritchie has entered into cal- a single candle-manufacturer who used culations, to show, that if the molecules of arsenic ; it had been ascertained that a water be assumed as incompressible, and when at the temperature of maximum small quantity of magnesia, or fresh chalk density, very nearly in absolute contact, acted similarly on the stearine, and to these we ought, in estimating the velocity of less injurious substances the tallow-chan.. 3ound in steam to add to the velocity given dlers now resorted.