Chemistry and Physics. 67 



5 X5X-|-mm., soldered edge to edge. The circuit was supported 

 by a torsion fiber and provided with a little mirror. With a mag- 

 netic field of only 100 units the instrument showed the heat which 

 would be cast on a half penny by a candle flame at a distance of 

 1168 feet. With a stronger magnetic field the instrument is 

 capable of much greater sensitiveness. The author calculates that 

 an instrument can be made which would show a change of tem- 

 perature at the junction of To~oTToTroTro °f a degree of heat. Mr. 

 Boys also showed a motor which consisted of a cross, the center 

 being antimony and the arms bismuth ; to the ends of the arms 

 are soldered four copper wires, the three ends of which are joined 

 by a ring of copper. When the spark from a blown out match is 

 held near this arrangement it rotates rapidly. If the spark is 

 held on the right hand side of the north pole the motor revolves 

 indifferently in either direction. If the spark is held on the left 

 hand side the motor stops. " We have, therefore, an electric mag- 

 netic motor which goes having neither sliding nor liquid con- 

 tacts." — Nature, April 7, 1887. J. t. 



9. Color mixtures. — At a meeting of the Physical Society in 

 Berlin, March 4, Professor Vogel exhibited an experiment which 

 can serve to dispel the popular notion that blue and yellow light 

 when mixed necessarily produce green. Three fluids were em- 

 ployed in three fiat phials. Phial No. 1 contained acid yellow 

 (Sauregelb); phial 2, solution of ammoniacal copper; phial 3, 

 aniline blue. 1 and 2 superimposed on each other gave green ; 

 1 and 3 a fiery red. — Nature, April 7, 1887. J. t. 



10. Dispersion of rock salt. — H. E. Ketteler discusses the recent 

 results of Professor Langley, applying a formula for dispersion 

 which he has lately published, Wied. Ann., xxx, p. 299, 1887. He 

 arrives at the following conclusion : " The member, —K1C of the 

 dispersion formula, expresses the absorption of radiant heat, and 

 all dispersion theories which do not take this into account are un- 

 tenable." — Ann. der PhysiJc and Chemie, No. 6, 1887, p. 322. 



J. T. 



11. Effect of pressure on thermometer bulbs. — Professor Spencer 

 Umf reville Pickering calls attention to errors which can arise from 

 a difference of pressure upon thin thermometer bulbs. When the 

 coefficient of expansion of the bulb is large, irregularities sufficient 

 to cause considerable errors may arise. The bulb subjected to 

 pressui'e apparently behaves like thin tin vessels where a small 

 addition or removal of pressure will cause a considerable altera- 

 tion in the form of the vessel. Glass cylinder bulbs were found 

 to be more rigid than spherical ones. — Phil. Mag., May, 1887, p. 

 406. j. t. 



12. On an objection to Professor Morley^s Attempt to explain 

 the less amount of Oxygen in the Air observed by him in the 

 region of an Anti-cyclone / by Max Schumann (from the "Mete- 

 orologische Zeitschrift," Bd. 4, June, 1884, translated by the 

 author.) — Mr. E. W. Morley explains in this Journal, III, vol. 

 xxii, p. 471, 1881, the result found by his experiments (contrary 



