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like wax. A borax bead volatilizes rapidly in white smoke. By moistening the end of a bent platinum wire, and dipping it into pure carbonate of lime or pure magnesia, and exposing it to the flame, a very fair exhibition of Hare's lime light, in min. iature, may be made. The fusion of a small iron wire, and the combustion with brilliant scintillations of a small steel watch spring may be exhibited as class experiments in a very striking manner.
Berzelius, in his work on the Blowpipe,* says, “I am convinced that the temperature produced by the blowpipe, fed by air from the lungs, has a distinctly defined limit; so that, for instance, alumina or silica cannot be melted, however small fragments of them be employed.” Now although I have not yet succeeded in producing large globules of fused silica, yet any person, by adopting the above expedients, may convince himself that the degree of heat thus obtainable is adequate for the fusion of silica. My experiments were made with chemically pure precipitated silica, and with a fragment of a colorless transparent crystal of quartz, from Herkimer county, New York, finely pulverized in an agate mortar. By taking a small platinum wire, bent as above, first fusing the end into a globule, then moistening this globule with saliva, or better in order to avoid the introduction of any trace of basic contamination, which might be supposed to form a fusible silicate), with syrup made from pure sugar, and dipping it into the powder, then gently heating and incinerating in the flame of a spirit lamp, the silica powder remains loosely attached to the wire, and under the lens appears now perfectly impalpable and devoid of transparency. If now the potash-tube blowpipe, with paraffine candle flame, be brought to bear upon it for a minute, the silica being held a little way outside of the point of the blue cone, which in this kind of flame appears to be the hottest point, it will then be found strongly adherent to the wire, as if melted fast, and under the lens presents the appearance of small, transparent, irregularly shaped globules, fused fast to the platinum. I have little doubt that with a large paraffine candle, and larger jet, a splinter of quartz might be fused.
The above mode of obtaining a high heat is essential to the practicability of a peculiar mode of manipulation that I have devised, and which I shall proceed to describe.
* Whitney's Translation, page 46.
+ Berzelius, in a note, mentions an announcement of H. de Saussure that he melted quartz, supported on a slip of kyanite, with a jet of air from a double bellows through the flame of a thick wax candle ; adding, however, that he suspects that “ the support may have produced an effect on the assay, and that the air from the bellows, being purer than that of the lungs, may have also contributed to effect a result which cannot be obtained by the mouth blowpipe."— Whitney's Translation, p. 54.
SECOND SERIES, VOL. XXVII, No. 80.- MARCH, 1859.
Many minerals and artificial products, when dissolved in a borax bead in large quantity, cause the bead to become opaque and milky on cooling, forming in fact an enamel, instead of a glass. Some of these are lime, magnesia, baryta, strontia, glucina, oxyds of zinc, cadmium and cerium, tungstic and titanic acids, calcite, magnesite, dolomite, witherite, baryto-calcite, strontianite, gypsum, epsomite, heavy spar, celestine, goslarite, smithsonite, fluor spar, apatite, sphene, aeschynite, polymignyte, yttro-tantalite, scheelite, scheeletine, xenotime, yttro-cerite, fluocerite, cryolite, &c. A great many more render the bead of microcosmic salt opaque or opalescent on cooling, and as some reactions, for instance that of titanic acid, are much more easily obtained in this than in the borax bead, these cases are also frequently of importance.
Now when it is desired to detect another substance occurring in small quantity in any of the above, such for instance as manganese, copper, cobalt, or titanium, by the color imparted to the bead after cooling, it is frequently impossible to do so, for the reason that if enough is added to give a decided reaction, the bead becomes opaque on cooling and the color cannot be seen.* In considering the cause of this loss of transparency, it seemed to me that it must be a granular crystallization, and remembering the fact that even common glass, if made to cool very slowly from fusion, becomes opaque and enamel-like, with many other familiar facts of an allied nature, it occurred to me that the converse of this phenomenon might also take place, or that an enamel which becomes transparent and vitreous when fused might retain its transparency when suddenly cooled. I was thus led to dip a bead composed of a highly basic borate of lime enamel into cold water while still fused. The result verified the hypothesis. The bead when cooled in this way remained transparent, and manganese was thus distinctly detected in a purely white marble, in which its presence could be distinctly pronounced upon otherwise only by Crum's test.
For a number of years I have had constant occasion to use this expedient, and have found it a highly valuable one. Blowpipe operators will need no further remarks upon the importance of such an addition to our facilities for investigation. It is necessary, however, that careful examination be made of all special cases, a work of time and patience, which I hope, nevertheless, soon to take up systematically.
As before intimated, it is necessary, or at least highly conducive, to the success of this new manipulation, to have means, such as are above detailed, of obtaining an increased heat; be
* Speaking of red zinc ore, Berzelius says that it is dissolved by phosphorus salt, but that the color of oxyd of manganese cannot be obtained till the glass has dissolved so large a quantity that it is no longer transparent on cooling."- Whitney's Translation, page 116.
hile additionar gas namire alone
cause these supersaturated beads, which enamelize (if I may be allowed to coin a new but convenient word) on spontaneous cooling, require a much higher temperature for fusion than those. which remain vitreous, and without some additional facilities for obtaining this higher heat, the tax upon the time and patience of the analyst becomes very onerous, and in many cases I have found it in fact impossible to succeed by the ordinary mode, for when the bead is very highly basic, it must be heated considerably above its point of fusion, or it solidifies to an enamel immediately on removal from the flame. It was this necessity which led me to devise the above modes of increasing the heat. It is by no means necessary, however, in ordinary cases, to use all of the expedients described. In fact, for the fusion of most of these borax enamels, the bent wire alone, with an ordinary blowpipe and an alcohol or gas flame, will suffice, and most others need only the additional assistance of the paraffine candle.
Whilst upon this subject of the blowpipe, I may be pardoned for offering briefly another suggestion. While making the experiments upon the reciprocal neutralization of the colors of metallic solutions, described in a former paper, * it struck me that the same principle should have applications in blowpipe analysis. It must be that when several metallic oxyds are present in a glass their several colors must interfere with each other in certain ways, and if we knew how to eliminate one or more of these colors by adding a neutralizing ingredient, so as to render others apparent, might it not furnish us with new facilities for research, and enable us to avoid old sources of error? I may conclude by noticing two or three results, which I have obtained, bearing upon this question. A deep amethystine bead of manganese glass acquired, on addition of a little oxyd of chrome, a gray color, resembling that produced by a mixture of solutions of chlorid of cobalt and chlorid of chromium, without any tinge of either red or green; a trifling additional quantity of oxyd of chrome giving, however, a distinct green color.t Another manganese bead gave a similar gray color on addition of oxyd of copper, but a slight excess of the latter imparted then a blueish tinge, which might easily be attributed to a trace of cobalt. The presence of nickel does not affect the blue color of a cobalt glass, as it does the rose color of cobalt in aqueous solutions, unless its quantity, compared with that of cobalt, is very great.
* Am. J. Science (2), xxvi, 49.
+ In the decoloration of ferriferous glass by the addition of deutoxyd of manganese, “glass-makers' soap," is the action wholly due to the conversion of the ferrous into ferric oxyd, or partly also to the neutralization of a portion of the green ferrous color by some violet manganese glass formed ?
ART. XXII.- On the Pendulum; by F. A. P. BARNARD, President of the University of Mississippi,—with a description of an Electric Clock, constructed by E. S. RITCHIE, of Boston, for the University of Mississippi, under the direction of President Barnard. With a Plate."
[From the Proceedings of the American Association at Baltimore, 1858.]
The importance of the pendulum as an instrument for the measurement of time, is sufficient to justify any amount of effort which may be made to secure the regularity of its performance. The causes which disturb this regularity exist partly in the nature of things, and are partly introduced by the contrivances employed to maintain the motion of the instrument. Among these, the effect of varying temperature in altering the distance between the centre of oscillation and the point of suspension, is one which has given occasion to many ingenious inventions; yet, however effectual some of these may have been in removing the irregularity due to this cause, it is probably true that no plan of compensation has been found in practice to be entirely satisfactory. It is an opinion entertained by the writer, though it is proposed with some diffidence, that the problem of compensation cannot be experimentally studied with results to be perfectly relied upon, so long as the pendulum has any work to do; and this must be the case whenever the maintaining power is derived, directly or indirectly, from a train of wheel-work. The different forms of anchor or pallet escapement involve friction upon the pallets, which, however nearly constant it may be, cannot be wholly so, and however slight it may be, either absolutely or in its variations, cannot be altogether insensible as a disturbing cause. For small as may be the amount of fluctuation in this resistance, it is to be considered that all the quantities concerned in the question of maintaining the motion of the pendulum are small, and that every minute variation is multiplied thousands of times. But a more serious cause of irregularity in the pendulum directly driven by a train, is to be looked for in the varying condition of the train itself, and of its lubricants; in consequence of which the power of the prime mover is to some extent absorbed, and is at different times unequally communicated to the pendulum.
When we attempt to study, in the actual performance of the pendulum, the efficacy of any plan of compensating the effects of temperature, it is impossible entirely to distinguish the irreg. ularities due to one cause from those which may proceed from another. Cold, for instance, by stiffening the lubricants may cause the clock to gain, and this effect may be erroneously ascribed to an under-compensation of the contraction of the pendulum-rod. And though, in such a case, if the clock should run more slowly than in warmer weather, we might justly infer an over-compensation to exist, we should be unable to determine exactly the excess.
The partial or total failure in practice of plans of compensation theoretically perfect, has been sometimes attributed to the unequal rapidity with which changes of temperature take place in different parts of the same pendulum. Every plan of compensation is necessarily founded on the supposition that, under all alterations of temperature, the temperature throughout the entire instrument is simultaneously the same. It is easy to see, for example, that if the mercury employed to compensate the pendulum of a common astronomical clock were to be wholly inclosed in a cylinder of some material entirely impervious to heat (supposing such a material to exist), it would be altogether useless for the purpose intended. And that which would thus be true, on the supposition that the mercury could not change its temperature at all, must be measurably so, if its changes of temperature lag behind those of the rod. Glass jars for containing the mercury in pendulums of this construction have been objected to, on the ground that they do introduce an irregularity of this sort; and accordingly Mr. Dent, the distinguished practical horologist of London, introduced in place of them cylinders of iron. The objection has been founded, I believe, rather upon the observed performance of the pendulums, than upon actual observation of the relative temperatures of the mercury and the rod. It would seem not to be difficult to arrange a pendulum with thermometers which should show constantly the true temperature both of the mercury and of the rod. And considering the importance of the question involved, such an experiment would appear to be well worth making, before pronouncing the mercurial compensation to be unsatisfactory, or even condemning the glass cylinders.
The escapements called remontoirs apparently set the pendulum free from most of the liabilities to disturbance which the train introduces. In clocks provided with these escapements, the force of the train itself is exerted not in impelling the pendulum, but in raising a small weight, or bending a slight spring, which subsequently acts—the former in its descent or the latter in its recoil-in moving the pendulum. The gravity-remontoir apparently furnishes an impelling force which is perfectly uniform, there being nothing but the very slight friction on the pivots of the arms carrying the remontoir weights to disturb this uniformity. The spring-remontoir is free from even this source of disturbance, but is open to a more serious objection, in consequence of the varying elasticity of the spring occasioned by change of temperature. Both of these contrivances, however,