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Note upon some phenomena of binocular vision
402
:~leehanics, Physics, and Chemistry.
to be, that an independe,at and most extensive and profitable iron manufacture can be established in the republic, notwithstanding the present declining state of the trade by reason of the opposition of Scotland and of Wales. Though iron be now made in Scotland at 30 per cent. less money than in Pennsylvania, it may come to pass that Pennsylvania may make iron at 30 per cent. below the prices now paid in Scotland or in Wales. And this will be the better event for the world at large. The iron manufacture is the foundation of all the arts of civilized existence. All nations should be able to furnish iron for themselves, for this metal is so !ndispensable that Sir Thomas Moore does not say too much in ranking iron as second only to the water that men must drink, or to the air that we must breathe; and a monopoly of iron by one nation is only less to the enslavement of the others, than though one alone possessed water to be sold to the remainder of the world. This is seen in the overwhelming wealth of England and the excessive poverty of Ireland, which is only produced by the coals and iron of England, and by the unfortunate deficiency of Ireland in coal fields worthy of the name. Ireland being therefore possessed of no iron furnace, and no one important manufacturing town, and thence its unemployed population, and the violence and desolation of that most miserable of lands. But when such inventions as the hot blast have produced consequences so extensive and so rapid in Scotland, it is not certain that the iron ores of Ireland may not be brought into profitable use in the early progress of the economical science of the present time. Equality of nations, as equality of individuals, is for the benefit of all; and though it is not desirable, and is not probable, that even all the superior advantages of the central State of the American Union, should enable iron to be sent to Scotland or to Wales, or do more than exchange the malleable bars of the Juniata for the hard railway iron of Wales, or for the fluid pig iron of the Clyde--yet are all the materials of the foundry and the forge to be seen by the eye of the traveler in the utmost profusion, for future'generations, who shall live amongst the dark blue outline of the mountains of Lebanon and the Juniata; and the neighboring carboniferous mountains of the Schuylkill, and the counties in that fortunate quarter of the republic of the United States. ~'~larch 7lh, 1849.
~'ote upon some phenomena of Binocular Vision. By M.~. FOUCAULTA~D J. REGNAULT, Translated for the Journalof the FranklinInstitute. MM. Foucault and J. Regnault have presented to the Academy of Sciences of Paris an account of some ingenious and beautiful experiments made by them, for the purpose of determining whether when the two fields of sight, or the corresponding portions of the two retin~e, were simultaneously impressed by light of different colors, a sensation of the compound color was produced. Mr. Wheatstone had affirmed that it was not--the general impression among observers appeared to be that it was. The instrument employed in this experiment was Mr. Wheatstone's stereoscop%
On the .Magnetic Power of Iron.
403
:rod the images observed were two screens of white paper, illuminated by zhe complementary,tints of color fi'om a polarising apparatus. Their resuits are as follows: "When the corresponding elements of the retina are impressed at the same time, alternations of activity and inertia of one of the eyes, show themselves generally at the commencement of the experiment, and there is perceived sometimes one of the tints, sometimes the other; but after an interval which varies ve U much in different individuals, there is seen only a single white circle. "When the eyes are in some degree accustomed to this unusual kin,! of impressions, the tendency to recomposition of the light is so great with some persons, that the screens may be passed through all the complementary tints wb.ieh the apparatus affords, without producing any corresponding sensalion of colors: the white light alone is seen. "By diminishing the intensity of one of the colors while the other remains constant, the reeomposition still lakes place; but the white disk appears more or less deeply tinged with the predominating colors. "When the intensities of the two complementary rays are simultaneously varied, it is observed that the recomposition takes place more easily at the commencement of the experiment, in proportion as their intensity is more moderate. "Among the complementa U colors which we have tried, the light blue and yellow are the most favorable for the experiment, and give the white immediately. Comptes Rendus de l'Aeademie des Sciences, aanuau, 1849.
After translating the above f,'om the Comptes Rendus, we found that ~he same results had been arrived at in the same manner, by an ingenious mechanic of our city, Mr. Return Sheble. tie had been struck with the singnlarity of the results given by Wheatstone's beautififl instrument, and constructed one for himself. In trying it about three )'ears ago, it occurred to him that since two perspective drawings placed in it produced upon the optic nerve the effect of a single object in relief, if the objects were differently colored, the effect of a compound color would be produced upon the eye. He tried the experiment by painting two cards, one yellow, the other blue, but was astonished to see "one color, as it were, through the ~ther." Upon repeating the experiment, however, about two months ago, with a red and green paint on each side of the stereoscope, he found that the impression produced was that of a dirty white. Red and yellow produced orange. Itis results striking]y confirm those above recorded. Ed. F. I. J.
0,~ lhe .Magnetic Power of Iron and ils .]Iclallu~gic Products. By M. A. DELESSE. (Second memoir'. Extract by the aulhor.) Translated for the Journal of the Franklin Institute.
The magnetic powers were determined by reducing the substance ~.') powder, the grains of which were of eq'aal size~an(1 aseertainir~,g :]l, TM
:~leehanics, Physics, and Chemistry.
to be, that an independe,at and most extensive and profitable iron manufacture can be established in the republic, notwithstanding the present declining state of the trade by reason of the opposition of Scotland and of Wales. Though iron be now made in Scotland at 30 per cent. less money than in Pennsylvania, it may come to pass that Pennsylvania may make iron at 30 per cent. below the prices now paid in Scotland or in Wales. And this will be the better event for the world at large. The iron manufacture is the foundation of all the arts of civilized existence. All nations should be able to furnish iron for themselves, for this metal is so !ndispensable that Sir Thomas Moore does not say too much in ranking iron as second only to the water that men must drink, or to the air that we must breathe; and a monopoly of iron by one nation is only less to the enslavement of the others, than though one alone possessed water to be sold to the remainder of the world. This is seen in the overwhelming wealth of England and the excessive poverty of Ireland, which is only produced by the coals and iron of England, and by the unfortunate deficiency of Ireland in coal fields worthy of the name. Ireland being therefore possessed of no iron furnace, and no one important manufacturing town, and thence its unemployed population, and the violence and desolation of that most miserable of lands. But when such inventions as the hot blast have produced consequences so extensive and so rapid in Scotland, it is not certain that the iron ores of Ireland may not be brought into profitable use in the early progress of the economical science of the present time. Equality of nations, as equality of individuals, is for the benefit of all; and though it is not desirable, and is not probable, that even all the superior advantages of the central State of the American Union, should enable iron to be sent to Scotland or to Wales, or do more than exchange the malleable bars of the Juniata for the hard railway iron of Wales, or for the fluid pig iron of the Clyde--yet are all the materials of the foundry and the forge to be seen by the eye of the traveler in the utmost profusion, for future'generations, who shall live amongst the dark blue outline of the mountains of Lebanon and the Juniata; and the neighboring carboniferous mountains of the Schuylkill, and the counties in that fortunate quarter of the republic of the United States. ~'~larch 7lh, 1849.
~'ote upon some phenomena of Binocular Vision. By M.~. FOUCAULTA~D J. REGNAULT, Translated for the Journalof the FranklinInstitute. MM. Foucault and J. Regnault have presented to the Academy of Sciences of Paris an account of some ingenious and beautiful experiments made by them, for the purpose of determining whether when the two fields of sight, or the corresponding portions of the two retin~e, were simultaneously impressed by light of different colors, a sensation of the compound color was produced. Mr. Wheatstone had affirmed that it was not--the general impression among observers appeared to be that it was. The instrument employed in this experiment was Mr. Wheatstone's stereoscop%
On the .Magnetic Power of Iron.
403
:rod the images observed were two screens of white paper, illuminated by zhe complementary,tints of color fi'om a polarising apparatus. Their resuits are as follows: "When the corresponding elements of the retina are impressed at the same time, alternations of activity and inertia of one of the eyes, show themselves generally at the commencement of the experiment, and there is perceived sometimes one of the tints, sometimes the other; but after an interval which varies ve U much in different individuals, there is seen only a single white circle. "When the eyes are in some degree accustomed to this unusual kin,! of impressions, the tendency to recomposition of the light is so great with some persons, that the screens may be passed through all the complementary tints wb.ieh the apparatus affords, without producing any corresponding sensalion of colors: the white light alone is seen. "By diminishing the intensity of one of the colors while the other remains constant, the reeomposition still lakes place; but the white disk appears more or less deeply tinged with the predominating colors. "When the intensities of the two complementary rays are simultaneously varied, it is observed that the recomposition takes place more easily at the commencement of the experiment, in proportion as their intensity is more moderate. "Among the complementa U colors which we have tried, the light blue and yellow are the most favorable for the experiment, and give the white immediately. Comptes Rendus de l'Aeademie des Sciences, aanuau, 1849.
After translating the above f,'om the Comptes Rendus, we found that ~he same results had been arrived at in the same manner, by an ingenious mechanic of our city, Mr. Return Sheble. tie had been struck with the singnlarity of the results given by Wheatstone's beautififl instrument, and constructed one for himself. In trying it about three )'ears ago, it occurred to him that since two perspective drawings placed in it produced upon the optic nerve the effect of a single object in relief, if the objects were differently colored, the effect of a compound color would be produced upon the eye. He tried the experiment by painting two cards, one yellow, the other blue, but was astonished to see "one color, as it were, through the ~ther." Upon repeating the experiment, however, about two months ago, with a red and green paint on each side of the stereoscope, he found that the impression produced was that of a dirty white. Red and yellow produced orange. Itis results striking]y confirm those above recorded. Ed. F. I. J.
0,~ lhe .Magnetic Power of Iron and ils .]Iclallu~gic Products. By M. A. DELESSE. (Second memoir'. Extract by the aulhor.) Translated for the Journal of the Franklin Institute.
The magnetic powers were determined by reducing the substance ~.') powder, the grains of which were of eq'aal size~an(1 aseertainir~,g :]l, TM