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The size of the uncharged atom of silver
I 14
EASTMAN KODAK COMPANY NOTES.
[J. F. I.
As with each of these surfaces a new free parameter is introduced, it is shown how much parameters can be utilized for satisfying other requirements in addition to that of the freedom f r o m aberration. In particular, a m e t h o d is developed for satisfying, by a system of two Cartesian surfaces, the sine-condition up to terms of the f o u r t h order and thus constructing an aplanatic lens properly so-called. In the last section it is shown how such a lens can be made achromatic .by the insertion o f a third surface, and the results here arrived at are illustrated on a complete numerical example.
The Size of the Uncharged A t o m of Silver. F. BIELZ. (Zeit. f. Physik., Vol. 3 2, No. 2 . ) - - A small ray of silver atoms passed through an aperture into an atmosphere of nitrogen. There were collisions between the atoms of the metal and the molecules of the gas, so that the ray possessed fewer and fewer atoms the farther i t was from the orifice. Three glass plates were exposed to the atomic stream, the silver there deposited was studied and from this the author deduces the important conclusion that the radius of the uncharged silver atom is one Angstr6m unit or I.o × Io -8 cm. Most other methods of arriving at the value of the radius give a larger result. G.F.S. O n the Electrification of W a t e r , S n o w and O t h e r Solids b y Fine Pulverization. H. KAEHLER and C. DORNO. (Ann. d. Pi~ysik., No. 9, 1925-)--Since different experimenters on this subject have reached contradictory results, the authors went to Davos in the Engadine last winter with the purpose of examining carefully the matters in dispute. There, partly sheltered by the eaves of the observatory, they set up a Faraday cage with a volume of I cm. in a locality where the earth's electrical field was weak. In the cage were a polonium collector to measure the volume charge and, in addition, an insulated brass plate to measure the charge of whatever fell on it. They made experiments with atomized water, dry snow, with meals of various sorts, with ashes, sand and dust. " From our experiments it is evident that in most cases the very finest dust is negatively charged . . . . The electrification comes from a mechanical separation of a double layer of electricity on the surface of the body with the negative electricity outside." They found in agreement with Lenard that in finely divided water the large drops are positive and the very small ones negative. They made another attempt to detect an electrical charge produced by the vaporization of water but, like their predecessors, they could find no charge thus caused. G. F. S.
EASTMAN KODAK COMPANY NOTES.
[J. F. I.
As with each of these surfaces a new free parameter is introduced, it is shown how much parameters can be utilized for satisfying other requirements in addition to that of the freedom f r o m aberration. In particular, a m e t h o d is developed for satisfying, by a system of two Cartesian surfaces, the sine-condition up to terms of the f o u r t h order and thus constructing an aplanatic lens properly so-called. In the last section it is shown how such a lens can be made achromatic .by the insertion o f a third surface, and the results here arrived at are illustrated on a complete numerical example.
The Size of the Uncharged A t o m of Silver. F. BIELZ. (Zeit. f. Physik., Vol. 3 2, No. 2 . ) - - A small ray of silver atoms passed through an aperture into an atmosphere of nitrogen. There were collisions between the atoms of the metal and the molecules of the gas, so that the ray possessed fewer and fewer atoms the farther i t was from the orifice. Three glass plates were exposed to the atomic stream, the silver there deposited was studied and from this the author deduces the important conclusion that the radius of the uncharged silver atom is one Angstr6m unit or I.o × Io -8 cm. Most other methods of arriving at the value of the radius give a larger result. G.F.S. O n the Electrification of W a t e r , S n o w and O t h e r Solids b y Fine Pulverization. H. KAEHLER and C. DORNO. (Ann. d. Pi~ysik., No. 9, 1925-)--Since different experimenters on this subject have reached contradictory results, the authors went to Davos in the Engadine last winter with the purpose of examining carefully the matters in dispute. There, partly sheltered by the eaves of the observatory, they set up a Faraday cage with a volume of I cm. in a locality where the earth's electrical field was weak. In the cage were a polonium collector to measure the volume charge and, in addition, an insulated brass plate to measure the charge of whatever fell on it. They made experiments with atomized water, dry snow, with meals of various sorts, with ashes, sand and dust. " From our experiments it is evident that in most cases the very finest dust is negatively charged . . . . The electrification comes from a mechanical separation of a double layer of electricity on the surface of the body with the negative electricity outside." They found in agreement with Lenard that in finely divided water the large drops are positive and the very small ones negative. They made another attempt to detect an electrical charge produced by the vaporization of water but, like their predecessors, they could find no charge thus caused. G. F. S.