12 JULY 1890, Page 24

Electrical Influence Machines. By J. Gray, B.Sc. (Whittaker and Co.)—This

is one of those useful handbooks on the variety of electrical machines which are always in request. Mr. Gray discourses fully—not too fully by any means—and somewhat technically about "Influence Machines." He describes a great many, and places their advantages and disadvantages clearly before the reader.