Page:Popular Science Monthly Volume 24.djvu/728

710 Latin, of the Province of Rio, composed in the last century by Fr. José Marianno da Conceição Velloso, and first published in 1825.

Grand Canon of the Colorado is characterized by some of the most wonderful rock-formations and the most gorgeous yet desolate scenery to be found anywhere on the earth. Captain Dutton has made the study and the description of it a labor of love, and the present volume, with its striking illustrations and the accompanying atlas with its grand panoramas and bird's-eye views, many of them, as well as the illustrations in the volume, colored according to nature, constitute one of the most welcome contributions to our literature and knowledge which the United States Geological Survey has made. Mr. Dutton's account of the geology, formation, characteristics, and scenery of the canon takes notice of every aspect in which the wonder is likely to be viewed. Among the details of the account, to which we would invite attention, are the carved niches or panels in the red-wall limestone, and the exquisite tracery of the rounded and inward curves and projected cusps of the walls, which are represented in plates 41 and 42 of the volume.

will carefully read Lieutenant Fiske's lucid exposition will have no excuse for persistence in the hazy notions concerning the relation of electrical effects, and the power requisite to produce them, not uncommon among even the intelligent and educated public. Very few persons, perhaps, are in the position, in regard to their knowledge of electricity, of the man who wanted to know why they should have a steam-engine and a dynamo-machine to make an incandescent lamp go, or of that English couple who purchased a Swan lamp and spent much time trying to light it with a match; but the ignorance which abounds on the subject is still very considerable. With the great and increasing development of the practical application of electricity, it is especially desirable that the general public, both in its character of investor and consumer, should have definite and clear conceptions of the fundamental principles involved in these applications. These Lieutenant Fiske has essayed to furnish in the present volume.

He introduces his subject with an elementary consideration of magnetism, which he follows with a chapter upon statical electricity. The relation of work and potential, and of the different electrical units to each other, is very clearly explained. A chapter is devoted to the laws of currents, and to primary and secondary batteries. In speaking of the electric light, no attempt is made, and very properly, to describe different forms, but to explain the essential principles involved in this class of apparatus. The chapter on electrical measurements is an admirable, concise statement of the subject, as is also that on telegraphy and on the telephone. The chapters upon electro-magnetic induction and upon the dynamo are excellent; but upon the latter Lieutenant Fiske might well have devoted some little attention to the designing of dynamos. He states in his preface that he intended his book to form a bridge between the theory of electricity and its practical application. There is probably no one case in which the practical constructor finds more difficulty, in passing from theory to practice than in this of the designing of dynamos. He may know what a unit magnet-pole is and the magnetic effect of a unit-current, but he still is able to but very vaguely see his way to apply this knowledge in determining the size of his field-magnets, the amount and size of wire on them, and the like proportions of his armature, to get the best results. Very few machines, we imagine, have been built so largely by rule of thumb as the dynamo, and therefore information of this sort could not fail of being of great value.

The book closes with a chapter upon the electric railway, giving a general view of the subject, and descriptions of the systems carried out by Siemens Brothers, and that devised by Mr. Edison and S. D. Field.