Review of Ferrini Book "Technological Physics: Electricity and Magnetism"

Fisica Tecnologica: Elettricità e Magnetismo. Nozioni fondamentali della Elettrotecnica illustrate da una compendiosa Esposizione delle principali Applicazioni nell’attuale loro Sviluppo.* By RINALDO FERRINI, Professor at the Higher Institution of Milan. Second edition, entirely re-written and illustrated with 169 figures. Milan: Ulrico Hoepli, 1896. 8vo., pp. 534.

Among the numerous important treatises on electricity, for which we are indebted to Italian authors, the volume before us may justly claim an honourable place.

In his preface, Prof. Ferrini objects to some of the names for electrotechnical units which have found their way into Italian, as well as into other European languages. He objects to the abridgments “volt” and “farad,” and would write these names in full. For “impedance” he would substitute “impediment”; for “voltage,” “electric pressure,” and for “shunt,” “derivation.” It may, however, be asked, whether it is not advantageous to have a set of identical terms used and understood by electricians in all countries, analogous to the names of weights and measures which have been introduced everywhere along with the metric system, and which are more cumbrous than the electrotechnical terms in question?

The first chapter of the work treats of electrostatics, and gives an exposition of the subject, which will not encounter any objections.

The second chapter takes up continuous currents and electrolysis. Among the practical applications of electrolysis there are some of unquestionable value, and others of doubtful utility. It has latterly been observed that aluminium obtained by the electrolytic process is liable to contain an impurity of sodium which, though small in amount, renders the metal very unstable, and open to destructive action (Comptes Rendus, cxxi., p. 794).

Goppelsroeder’s electric production of coal-tar colours has not yet come into use on a commercial scale. Hermite’s treatment of sewage, which is certainly practicable in maritime localities, is open to one grave objection, the organic nitrogen, or “allumenoid ammonia,” and the other nitrogen compounds, are either decomposed, or allowed to remain in a soluble state, and consequently unutilised. Now, the great desideratum in the treatment of sewage, is to obtain all the nitrogenous compounds in such a form that they may be applicable to the land. Whether the effluent water from Hermite’s process can be advantageously used in irrigation is yet undecided.

That copper can be refined electrically in a satisfactory manner is unquestionable. To the value of the Elmore process (which is here mentioned) we need not refer.

In the same chapter we have an account of the primary couples and batteries of Clamond, Gülcher, Smee, Grove, Bunsen and Daniell. In the table of electro-chemical equivalents (p. 91) we find no mention of platinum, but on p. 116 is a more complete table of the specific resistances of metals and alloys.

In tabulating the electric units with their definitions, the author proposes a set of symbols, such as C for the coulomb, A for the ampere, O for the ohm, V for the volt, F for the farad, J for the joule, and W for the watt.

The third chapter discusses magnetic induction. We find here an account of aperiodic and ballistic galvanometers, of the galvanometer of Arsonval, the solenoid amperemeter or ammeter, the electro-dynamometer, the thermic ammeter, the Carpentier electrometer, the Siemens and Cardew voltmeters, and the wattmeter.

The fourth chapter treats of induction currents, and the fifth is devoted to dynamos, motors, and what may be in great part called the mechanical applications of electricity. There is an account of electric motors, continuous and alternating, of polyphase motors, of the monophase motors of Brown, of Benisohke’s asynchronous motor, and of transformers.

Electric lighting is duly considered, as is natural in a work written in a country so rich in water-power as is Italy. The experiments of Tesla are not overlooked; but it is remarked that the conditions for such illumination are as yet much less advantageous than is the case with ordinary electric lamps.

The question of protection against lightning the author rightly regards as requiring further study. The disaster to the Town Hall of Brussels, though fitted with conductors according to the Franklin principle, all in perfect order, is unpleasantly significant.

* Technological Physics: Electricity and Magnetism. The fundamental notions of electrotechnics illustrated in a compendious exposition of their principal applications.