310 Scientific Intelligence. 
upon one more internal—and made the supposition that were it 
i h 
piece of iron free from the influence of the 
tion of an external inducing force upon a bar of iron or steel is 
the result of symmetrically opposed polar forces, producing 
apparent waves of opposite polarity, or reactions between the 
exterior and interior of a bar of iron.” . 
3. Report on the Internutional Exhibition of Electricity held 
at Paris, August to November, 1881; by Major Davip 
Hxap, Corps of Engineers, U.S. A. 287 pp. 8vo. Washington, 
1884 (Engineer Department, U. S. A.).—This volume contains 
brief descriptions of many of the electrical arrangements exhibited 
at the Paris Exhibition ; these include many forms of batteries, 
dynamo and magneto electric machines, electro-motors, electric 
lamps, light houses and soon. The value of the descriptions 
given is increased by the fact that they are profusely illustrated. 
This publication has additional interest at the present moment 1n- 
view of the similar exhibition now being held at Philadelphia. 
4, The Modern High Explosives. Nitro-glycerine and Dyna 
mite: their manufacture, their use and their application ppc 
-cot 
principal nitro-compounds; by Manvet E1ssier, Mining Engineer. 
y & Sons).—The title. 
explosives, describing also the use of electricity in blasting opeTa 
tions; and the third gives the principles of blasting, the force - 
oO e 
es, the 
i 
destruction of walls, various obstructions as in navigation oF 1) 
agriculture, and soon. The volume contains a large amount of 
useful information much needed in view of the constantly incre ae 
ing use 0 h explosives, and the often comparative ignorance 
5. Light; by P. G. Tait, M.A., ete. 276 pp. 12mo. Edin- 
burgh, 1884 (Adam and Charles Black),.—Professor Tait’s excel- 
lent little treatise on Heat, noticed in a recent number of this 
