Chemistry and Physics. 487 © 
oles of an electro magnet, and publishes a table in which he 
finds great agreement between the direction of the Hall effect 
and the thermo-electric effect of strain in different metals. Mr. 
Hall has replied in Science, March 28, 1884, and shows that if the 
Strain is proportional to the magnetic force, as Mr. Bidwell sup- 
poses, the Hall effect should be proportional not to the current, as 
actually is the case, but to the cube of the current. 
Professor 8S. P. Thompson and Mr. C. C. Starling have also 
varied Dr. Hall’s experiment by using a very large sheet of tin 
foil, so that the wires and connections should be entirely outside 
Peltier effect in the thin strip of metal interposed between the 
] . 
Danient, M.A., Lecturer on Physics in the School of Medicine, 
Edinburgh. 653 pp. . London, 1884 (Macmillan & Co.).— 
Teachers of Physical Science will welcome a text-book, which 
Summary ot physical phenomena. According to the modern 
the development of heat, sound, radiant energy, electricity and 
magnetism. These latter subjects, consequently, ty treated in 
: ; arli 
Anprew Gray, M.A., ete. 207 pp. 12mo, London, 1884 (Mac- 
millan & Co.).—The universal adoption by electricians of the 
Series of electrical units, based upon the absolute system, which 
was recommended by the Paris Congress of 1881, has served to 
put electrical measurements upou a basis of precision, which was 
Impossible as long as the old methods were adhered to. This 
little volume of Mr. Gray starts with the explanation of the rela- 
tions of these units, and goes on to develop the principles involved 
in absolute measurements, and the practical methods and instru- 
ments employed in them. The subject is one of great importance 
