Chemistry and Physics. 301 



11. Heat. By Mark R. Wright. 12mo, pp. x, 336. New 

 York, 1893. (Longmans, Green & Co.). — This book forms one of 

 the manuals issued for students in advanced classes. It treats 

 the subject from the basis of fact rather than of theory, the 

 nature of heat not being discussed until the second third of the vol- 

 ume. The statements appear accurate and the illustrations good. 

 Radiation is still included as a department of heat proper. Num- 

 erous questions and problems are given at the end of the chap- 

 ters. The subject of Thermodynamics is exceptionally well 

 treated. G. r. b. 



12. A Select Bibliography of Chemistry, 1492-1802, by H. C. 

 Boltox. 1212 pp. 8vo, No, 850 of the Smithsonian Miscellaneous 

 collections. — This volume is the result of an immense amount 

 of careful work. Coming from Prof. Bolton, it is sure to be 

 accurate work. Chemists owe him a great debt of gratitude for 

 this " labor of love." 



13. Interferences of electrical waves produced by normal 

 reflection from a metallic plate. — According to the researches of 

 Hertz, long electrical waves apparently travel faster in air than 

 along wires, while the velocities in the two media are sensibly 

 equal for short waves (X = 30 cm ). MM. Sarasin and de la Rive 

 have instituted experiments on a large scale to test the question 

 of this inequality in the rate of propagation. A building con- 

 nected with forces motrices du Rhone at Geneva was placed at 

 their disposal. A metallic reflecting surface 8 m in height and 

 16 m in breadth of zinc , 5 mm in thickness was placed against a wall 

 of the interior of the building, and a camera-like box 10 m long 

 and l'50 m wide made of black paper rested against the metallic 

 surface and projected into the room. This dark chamber was 

 supported at such a height that a normal through its center to the 

 metallic surface was 4 m above the floor. A species of optical 

 bank ran through the center of the dark chamber on which the 

 various resonators which were used were mounted. 



The apparatus for producing the electric sparks did not differ 

 essentially from that employed by Hertz with the exception that 

 the Ruhmkorf coil was excited by a dynamo machine. The 

 spark apparatus was placed at a height of 4 m and 15 m from the 

 mirror. By moving the resonators to and fro in the dark chamber, 

 points of interference of the direct and the reflected waves were 

 obtained. In one case a resonator of 0'75 m in diameter was 

 employed. It consisted of a hollow tube of copper bent into a 

 circle. The exterior diameter of the tube was l cm , and one end 

 of the tube was provided with a suitable micrometer in order to 

 measure the spark gap. It was found that a reflecting surface of 

 at least 12 m to 14 m in length and 8 m in height was necessary to 

 produce the phenomena with a resonator # v5 m in diameter, and a 

 surface 8 m by 8 m to produce them with a resonator 0*05 ra in dia- 

 meter. The author's conclusions are as follows : 



The circular resonator responds to a constant wave length, 

 whatever maybe the dimensions of the exciter; the intensity 



