Chemistry and Physics. 67 



with suitable magnets or pieces of iron, which are controlled by 

 a movable magnetic field, the strength of which can be suitably 

 altered by moving these magnets beneath or in the neighborhood 

 of the needle. The needle of the electrometer was connected 

 to earth, and the quadrants were alternately connected to the 

 source of electricity. In this way a deflection was produced by 

 induction, and if s and s' are deflections, and V and V' potentials, 

 we have s : s, — V 2 : V ; a . The changeable magnetic field gives 

 the instrument a great range. — Ann. der Physik und Chemie, 

 No. 6, 1888, pp. 286-298. J. T. 



6. Fluor esce?ice. — It is known that the fluorescence of liquids 

 increases very greatly to a certain point with the dilution of the 

 fluorescing medium. B. Walter discusses the reason of this 

 phenomenon, and shows that it depends upon the amount of light 

 absorbed by the fluorescent substance. Strongly fluorescing sub- 

 stances, like magdala red, eosine, chlorophyl, etc., in the solid 

 state, show no fluorescence, and the author believes that fluores- 

 cence hitherto observed in solid bodies can be traced to water of 

 crystallization or other thinning medium. If A denote the 

 amount of light absorbed by the substance, Fl the amount of 

 light emitted by fluorescence, the fraction Fl/A can denote the 

 fluorescing power of the medium. In the case of eosine, with a 

 dilution of -J, the value of this fraction was -000663 ; with 2Trs ^ s 

 value was -009126. — Ann. der Physik und Chemie, 1888, No. 6, 

 pp. 316-326. j. t. 



7. Grunicald' 's hypothesis in s}iectrum analysis. — Dr. A. Grun- 

 wald continues to give the results of his remarkable hypothesis 

 and reserves to a later paper the description of the steps by 

 means of which he obtains certain relations between groups of 

 spectral lines. In his paper to which this notice refers, will' be 

 found a number of numerical results. Oxygen he thinks is com- 

 posed of a substance A' combined with another substance O'; 

 this substance O' being a compound with the formula b£)\\ 

 where O" is again a compound 6 4 c 5 ; so that 0=H'6 4 (# 4 c 5 ) 5 . He 

 had previously shown that, according to his hypothesis, hydro- 

 gen is composed of two primary elements, a and b ; and now 

 gives various criteria by means of which a, b and c can be recog- 

 nized in magnesium and carbon. — Phil. Mag., May, 1888, pp. 

 343-350. j. t. 



8. Penetration of Day-light in the water of Lake Geneva and 

 of the Mediterranean. — MM. Fol and Sarasix give a summary 

 of the results obtained by them in regard to the penetration of 

 clay-light in clear water. They employed sensitive photographic 

 plates, so arranged with a new apparatus^ that they could be ex- 

 posed for the time selected, say ten minutes, at any desired depth, 

 as 100, 200 or 300 meters, etc. In the first trials made 

 it was found that the effect was stronger on September 28th, 

 with a cloudy sky, than on August 16th, with fine weather; 

 more particularly they found that in the former month the 

 amount of light at a depth of 170 meters was comparable to that 



