October 29, 1886.] 



SCIENCE. 



397 



framing a question about the first name or sub- 

 ject on the page. Such questions are a severe tax 

 on a librarian's time and patience ; but, if a reader 

 comes in search of answers, he must be kindly 

 received, and all the resources of the library placed 

 at his disposal. A librarian needs a certain tact 

 and skill in guessing at the wants of readers. 

 This comes by practice, after one has learned to 

 estimate the mind-power of the frequenters of a 

 library. ' Can you give me souiething on the 

 French revolution ? ' asks a young girl. Instead 

 of offering Thiers, or Carlyle, or even the 

 ' Epoch of history ' volume, the librarian asks, 

 ' How long an account do you wish, — one in sev- 

 eral volumes ? ' — ' Oh, not very long, and not 

 very deep, please.' — 'An historical novel, per- 

 haps ? ' — ' Yes,' with a visible brighteniug of the 

 face ; and the reader goes home happy with 

 ' Citoyenne Jacqueline,' perhaps to come back and 

 ask for another novel of the same period, or even 

 a history. It is, however, too much to expect 

 that every reader who desires a Little historical 

 knowledge will go through a course of many- 

 volumed books. The various lists of historical 

 novels published by the Boston public library and 

 other libraries. Professor Allen's 'Catalogue of 

 novels and poems on English history,' and Adams's 

 ' Manual of historical literature,' are every-day 

 helps in eren the smallest library. It is not hard 

 for a librarian to make a list of the novels in his 

 or her own library which illustrate different 

 periods. A small library has this advantage over 

 a large one, that it cannot afford to buy poor 

 novels. Miss Hewins closed with a list of about 

 seven hundred dollars' worth of books made for 

 the beginning of a free library in a manufactur- 

 ing and farming town, whose inhabitants are of 

 average intelligence. 



THE AGE OF ELECTRICITY. 



In the closing sentencie of this book the author 

 remarks that we are to-day entering upon the age 

 of electricity ; so that, in spite of its title, the 

 volume must be regarded as a discussion of inci- 

 dents in the world's history which were necessary 

 and preliminary to its complete preparation for the 

 phase of its existence which it is now about to 

 take on. Now and then, throughout its nearly 

 four hundred pages, prophetic glimpses are afforded 

 of what this age may have in store for us, but in 

 the main the author has confined himself to the 

 safer ground of already accomplished fact. 



The reader is carried from the ' myth of the 

 amber-soul,' which is discoursed upon in the first 



The age of electricity. By Park Benjamin. New York, 

 Scribner, 1886. la". 



chapter, to nearly the latest application filed in 

 the patent office up to date ; and, in a general 

 way, the task of summarizing the vast amount of 

 information which scattered itself with great 

 irregularity along the centuries from the earliest 

 of these dates to the latest has been well and 

 satisfactorily performed. 



The book is written in the interests of the 

 general public, and is nearly free from technicali- 

 ties, which are so often a bugbear to the general 

 reader. While not especially intended for the 

 student of electricity, it wiU prove to be a useful 

 book of reference to many whose collections are 

 limited, as it contains a good deal of historical 

 information not otherwise accessible in a single 

 volume. Considered in relation to the supposed 

 demands of the general reader, the author has 

 perhaps erred somewhat in often going into details 

 which may serve to complicate rather than to 

 simplify, and, in a few instances, in avoiding the 

 discussion of an interesting subject because of its 

 seeming difficulty. 



Several inaccurate and misleading statements 

 are found scattered through the book, which are 

 all the more noticeable on account of its general 

 excellence. Early in his discussion the author 

 defines the units now commonly used in electrical 

 measm-ement : but he has not been able to avoid 

 confusion in their use subsequently, as when he 

 states that the quantity of current necessary to 

 decompose a grain of water is 3.13 amperes, and in 

 other instances. Many readers will be astonished 

 at the statement that the resistance of a battery- 

 cell is in no way altered by increasing or diminish- 

 ing the size of the plates. The assumption of the 

 resistance of what the author continually calls a 

 ' strange atmosphere ' around the poles of a mag- 

 net, and in the neighborhood of a conductor con- 

 veying a current, in order to account for the phe- 

 nomena of the magnetic field, would hardly seem 

 to be warranted, even in a popular treatment of 

 the subject. 



In his historical references, the author is dis- 

 posed to give due credit to American science and 

 invention, although in his discussion of the induc- 

 tion coil he nowhere mentions the important con- 

 tributions of Mr. E. L. Ritchie ; and his treatment 

 of contemporaneous discovery and invention does 

 not seem to be quite free from prejudice and bias. 



Notwithstanding these and some other faults, 

 the book contains a vast amount of interesting in- 

 formation, presented in an interesting way, and it 

 will doubtless find an appreciative audience. It 

 presents a handsome appearance, and the numer- 

 ous illustrations are generally appropriate adjuncts 

 to the text. In the fine full-page cut, however, 

 showing a man of war destroyed by a fish-torpedo, 



