428 Scientific Intelligence. 



Physical Society of Berlin, June I, 1894; Ann. der Physik und 

 Chemie, pp. 57, 58. j. t. 



11. Motion of dielectric bodies in a homogeneous electrostatic 

 field. — Le Graetz and L. Fomm describe a dielectric volmeter 



which consists of a thin disc of sulphur or paraffin suspended 

 between the plates of a condenser. The disc tends to place its 

 axis along the lines of electrostatic force. The rotations depend 

 on the size of the charge on the plate, and the oscillations are 

 proportional to the square of the difference of potential. — Ann. 

 der Physik und Chemie, No. 9, 1894, pp. 86-94. j. t. 



12. Maxim's flying machine. — Mr. Hiram S. Maxim gives in 

 the National — an English magazine — a description of his experi- 

 ments on flying by means of an aeroplane. His flying machine 

 when finished and loaded with water, fuel and three men, weighed 

 nearly 8000 lbs. The actual horse power developed on the screws 

 was 363 horse power, with a screw thrust of about 2000 lbs. The 

 total width of the machine was over 200 feet. On running the 

 machine at 30 miles an hour very little load remained on the 

 track and at 36 miles an hour the whole machine was completely 

 lifted. — Nature, Sept. 13, p. 489. j. t. 



13. A Treatise on the Measurement of Electrical Resistance. By 

 William Arthur Price, M.A., A.M.I.C.E. 8°, pp. xvi, 199. 

 Oxford, Clarendon Press, 1894. — This volume is an exposition of 

 the theory and practice of the measurement of electrical resist- 

 ance, with especial reference to those considerations that ai'ise in 

 actual work, and which are either altogether omitted in ordinary 

 general treatises, or very insufficiently presented. In the first 

 chapter the meaning of resistance, its laws, and units of measure- 

 ment are considered. This is followed in the second chapter by 

 a discussion of the materials best suited for resistance coils, their 

 temperature coefficients, their variation with time, and attention 

 is drawn to the special qualities of some of the newer materials, 

 as platinoid and manganin. In succeeding chapters the construc- 

 tion of bobbins, the best methods of winding resistance coils, 

 and the precautions to be observed in order to secure accuracy 

 and permanence are taken up. The various forms of commutators 

 and switches, Wheatstone's bridge, the meter bridge in its later 

 modifications, with the various accessories and adaptations, the 

 most suitable arrangements for very low or very high resistance 

 are discussed in detail. 



In several Appendices are contained the mathematical theory 

 of Wheatstone's bridge, Lord Kelvin's modification of it for low 

 resistances, electromotive forces at the junctions of meter bridges,, 

 the discharge of a condenser through a high resistance, Mance's 

 method of measuring the resistance of a battery, and the electro- 

 static analogue of Wheatstone's bridge. 



The pages of the book contain many interesting remarks and 

 practical suggestions derived from experience, and will be a valu- 

 able aid to those studying the subject in a general way, and 



