TY - JOUR
AB - American Journal of Science, September. — Fireball of January 13, by H. A. Newton (see p. 524).—On a photometric method which is independent of colour, by Ogden N. Rood. This is not based, like most previous methods, upon the comparison of the luminosities of two adjacent surfaces, but upon the shock that is produced upon the retina by a change of intensity of light. If one-half of a rotating disc reflects less light than the other by 1–50th of the whole amount, with appropriate rates of rotation a faint flickering will be noticed. This flickering disappears if the two halves have the same degree of brightness, whatever may be their colours.—On the oscillations of lightning discharges and of the Aurora Borealis, by John Trowbridge. Photographs were obtained of sparks having both great electromotive force and great quantity, produced by an alternating machine giving from 300 to 400 alternations per second, with the aid of a step-up transformer and an oil condenser. The oscillations were investigated by Feddersen's rotating mirror method. The sparks were about 2 cm. long, and the interval between two successive oscillations was one hundred-thousandth of a second. On each of the photographs reproduced some ten or twelve oscillations can be counted. The discharge is seen to follow exactly the same path three times in succession. After that it assumes the character of a brush discharge. By intercalating a non-inductive water resistance and a vacuum tube between the terminals of a suitable transformer it is possible to imitate exactly the phenomena observed when a vacuum tube is held in one hand while the other hand grasps the terminal of the transformer. In observiug the striæ and waving columnar form of the light excited in this manner in tubes filled with rarefied gases, one is led to believe that the stratified form of the Aurora Borealis is produced in a similar manner.—On the estimation of chlorates and nitrates, and of nitrites and nitrates in one operation, by Charlotte F. Roberts. By means of the apparatus for the estimation of nitrates previously described, chlorates and nitrates together may be estimated. They are treated with manganous chloride, and the resulting gases are passed through potassium iodide and then into a Hempel's burette. The amount of nitric oxide, gives the amount of nitrate present, and the chlorate is estimated by deducting from the total chlorine liberated that due to the reduction of the nitrate.
TI - Scientific Serials
JF - Nature
DO - 10.1038/048535a0
DA - 1893-09-28
UR - https://www.deepdyve.com/lp/springer-journals/scientific-serials-C2ZZv0gphJ
SP - 535
EP - 535
VL - 48
IS - 1248
DP - DeepDyve
ER -