Vietnam or Thailand ? Vote for the TOP Country of the Week !
Updated: May 8, 2025
The accompanying engraving shows a form of Thomson's double bridge, as modified by Kirchhoff and Hausemann. The chief advantage claimed for this instrument consists in the fact that all resistances of defective contact between the piece to be measured and the battery are entirely eliminated an object of prime importance in measuring very small resistances.
These bright lines are produced with particular intensity by the yellow flame derived from a mixture of salt and alcohol. They are in fact the lines of sodium vapour. Kirchhoff produced a spectrum by permitting the sunlight to enter his telescope by a slit and prism, and in front of the slit he placed the yellow sodium flame.
In his second paper, communicated to the Berlin Academy before the close of 1859, Kirchhoff proved the existence of iron in the sun. The bright lines of the spectrum of iron vapour are exceedingly numerous, and 65 of them were subsequently proved by Kirchhoff to be absolutely identical in position with 65 dark Fraunhofer's lines.
His beautiful experiment remained a germ without fruit, until the discernment, ten years subsequently, of the whole class of phenomena to which it belongs, enabled Kirchhoff to solve these great problems.
Kirchhoff immediately inferred from it that the salt flame, which could intensify so remarkably the dark lines of Fraunhofer, ought also to be able to produce them. The spectrum of the Drummond light is known to exhibit the two bright lines of sodium, which, however, gradually disappear as the modicum of sodium, contained as an impurity in the incandescent lime, is exhausted.
With Thalèn, he besides added manganese, titanium, and cobalt to the constituents of the sun enumerated by Kirchhoff, and raised the number of identical rays in the solar and terrestrial spectra of iron to no less than 460. Thus, when Sir Norman Lockyer entered on that branch of inquiry in 1872, fourteen substances were recognised as common to the earth and sun.
These memorable results were founded upon a general principle first enunciated by Kirchhoff in a communication to the Berlin Academy, December 15, 1859, and afterwards more fully developed by him.
The way was paved for this discovery by a succession of chemists and opticians, Fraunhofer , Brewster , Sir John Herschel , J. W. Draper, and others; but the instrument was devised by Kirchhoff and Bunsen. Instantaneous photography has been of much service in the observation of eclipses and other astronomical phenomena. Progress has also been made in color-photography.
As long ago as 1858, Kirchhoff, by attributing to saline solutions that is to say, to mixtures of water and a non-volatile liquid like sulphuric acid the properties of internal energy, discovered a relation between the quantity of heat given out on the addition of a certain quantity of water to a solution and the variations to which condensation and temperature subject the vapour-tension of the solution.
The sun, according to Kirchhoff, consists of a molten nucleus which is surrounded by a flaming atmosphere of lower temperature. The nucleus may, in part, be clouds, mixed with, or underlying true vapour.
Word Of The Day
Others Looking