July 12, 1889.] 



SCIENCE, 



31 



Becker in Leipzig, Dr. Frankel in- Berlin, and Dr. Frank in Naples. 

 These are all members of the younger generation of instructors, 

 and are adepts in the laboratory methods of Koch. Dr. Fischer's 

 original work has been exerted in two directions chiefly, — one in 

 the application of bromine to disinfection, another in the study of 

 the phosphorescence of the sea. 



ELECTRICAL NEWS. 



New Form of Gas-Battery. — This battery, invented by 

 Mr. Ludwig Mond and Dr. Carl Langer, is an improvement on the 

 gas-battery invented by Grove fifty years ago, which produces 

 electricity from hydrogen and oxygen gas by the intervention of 

 platinum. The distinguishing feature of the new battery, which 

 has been designed to obtain large currents of electricity by means 

 of these gases, is, according to Nature, that the electrolyte is not 

 employed as a mobile liquid, but in a quasi-solid form, and it is 

 therefore named " dry gas battery." Each element of the battery 

 consists of a porous diaphragm of a non-conducting material, — for 

 instance, plaster-of- Paris, — which is impregnated with dilute sul- 

 phuric acid. Both sides of this diaphragm are covered with very 

 fine platinum-leaf, perforated with very numerous small holes, and 

 over this with a thin film of platinum black. Both these coatings 

 are in contact with frameworks of lead and antimony, insulated 

 one from the other, which conduct the electricity to the poles of 

 each element. A number of these elements are placed side by 

 side, or one above the other, with non-conductmg frames inter- 

 vening, so as to form chambers through which hydrogen-gas is 

 passed along one side of the element, and air along the other. One 

 element, with a total effective surface of 774 square centimetres 

 (120 square inches), which is covered by i gram of platinum black 

 and .35 of a gram of platinum-leaf, shows an electro-motive force 

 of very nearly i volt when open, and produces a current of 2 am- 

 peres and .7 of a volt, or 1.4 watts, when the outer resistance is 

 properly adjusted. This current is equal to nearly 50 per cent of 

 the total energy obtainable from the hydrogen absorbed in the bat- 

 tery. The electro-motive force decreases, however, slowly, in con- 

 sequence of the transport of the sulphuric acid from one side of 

 the diaphragm to the other. In order to counteract this disturbing 

 influence, the gases are from time to time interchanged. The 

 battery works equally well with gases containing 30 to 40 per cent 

 of hydrogen, such as can be obtained by the action of steam, or 

 steam and air, on coal or coke, if the gases have been sufficiently 

 purified from carbonic oxide and hydrocarbons. The water pro- 

 duced in the battery by the combination of hydrogen and o.xygen is 

 carried off by the unconsumed nitrogen, and an excess of air carried 

 through it for this purpose. 



BOOK-REVIEWS. 



Education z'» the Utiited States : its History from the Earliest 

 Settlements. (International Education Series.) By Richard 

 G. Boone. New York, Appleton. 12". $1.50. 

 This book belongs to a class that are becoming rather common 

 in this country, books presenting a large amount of useful informa- 

 tion in an unattractive style. The time has been when a good lit- 

 erary style was considered indispensable in an historical work ; but 

 in our time, and especially in this country, we are treated to vol- 

 ume after volume on historical themes in which style is utterly 

 lacking. That this should be so is somewhat surprising ; for a 

 work that has no charm of style is certain to have a much smaller 

 circle of readers than one that has that attraction, and writers 

 usually desire as many readers as possible. In Mr. Boone's book 

 we are sorry to find this literary defect ; for the work has a good 

 deal of merit of other kinds, conveying as it does a large amount 

 of information for the most part well arranged. It has evidently 

 been prepared by careful and conscientious study of the original 

 authorities, and will be useful at least to all educators and as a 

 work of reference to all intelligent readers. It opens with an ac- 

 count of the steps taken by the early colonists to establish schools 

 and colleges, and shows how, at the very outset of our national 

 history, the sentiments of North and South differed on this subject 



of education. Massachusetts and Connecticut led the way in 

 founding schools for the whole people, and it was not until com- 

 paratively recent times that their ideas and practice became gen- 

 erally prevalent. How the public-school system grew up and over- 

 spread the country, Mr. Boone relates at considerable length ; and 

 he does not fail to show how much the schools have been improved 

 by the increase of State control. Then follows a chapter on recent 

 progress in the colleges, showing the changes in the curriculum, 

 the introduction of the elective system, and other matters of inter- 

 est. Professional and technological schools are also treated of, and 

 there is a chapter on the education of the deaf and dumb and 

 other unfortunates, and of criminals. The author does not con- 

 fine himself, however, to the schools alone, but gives the history of 

 other educational agencies, such as libraries, museums, and learned 

 societies. The founding of the Smithsonian Institution, the grants 

 of land for educational purposes, and other acts of the general 

 government bearing on education, are related ; and the book closes 

 with an interesting chapter on the advance that has been made in 

 the education of women. Thus it contains a valuable mass of in- 

 formation, which, so far as we know, was not accessible before in 

 a convenient form. 



A Theoretical and Practical Treatise on the Strength of Beams 

 and Girders. By Robert H. COUSINS. New York, Spon. 

 12°. S5. 

 Since the time of Galileo, the subject of which this volume 

 treats has received much attention at the hands of the ablest 

 mathematicians of all countries. Many attempts have been made 

 during the present century to solve experimentally the problems in- 

 volved, only to result in the adoption, by many experimenters, of 

 empirical rules for the strength of beams and girders, rather than 

 scientifically deduced formulas ; the reason for this, as given by 

 one authority, being that " no theory of the rupture of a simple 

 beam has yet been proposed which fully satisfies the critical experi- 

 menter." The theory advanced in this treatise, and the formulas 

 resulting from that theory, deduce the strength of beams and 

 girders from the direct crushing and tensile strength of the ma- 

 terial composing them, leaving out of the problem altogether the 

 co-efficient known as the modulus of rupture. The theory and 

 the formulas deduced from it are in accord with correct mechanical 

 and mathematical principles, and the author believes that they will 

 fully satisfy the results obtained by the experimenter. Works of 

 this character derive special importance from the constantly in- 

 creasing use of iron and steel for building and engineering pur- 

 poses. 



The Beginners' Book in German. By Sophie Doriot. Boston, 

 Ginn. 12°. 90 cents. 



This Httle book is the result of the need felt by the author and 

 others, in teaching German, of suitable books to put into the hands 

 of beginners. It consists of two parts. Part I. is a series of les- 

 sons, each of which is introduced with a picture, followed by cor- 

 responding verses from the child-literature of Germany. These 

 pictures, which illustrate the text following, were all drawn ex- 

 pressly for the purpose, and are brimming with the spirit of fun and 

 humor which they have so faithfully caught from the child-lore. A 

 conversation upon the subject, with the study of words and 

 phrases, completes each lesson. In this way advantage is taken 

 of the children's tastes and inclinations, and even of the mischief- 

 loving element which enters so largely into the child-nature. The 

 second part contains graded selections for reading. 



The typography and make-up are in every way excellent. The 

 book, as a whole, forms a very attractive volume, and we have no 

 doubt that it will prove, as the author has intended, a great relief 

 to teachers and a source of pleasure to pupils. 



The A B C of Electricity. By William H. Meadowcroft. 

 New York, F. W. Lovell. 12°. 50 cents. 

 Condensation of matter and simplicity of language are the 

 points most noticeable in this little volume. A brief general out- 

 line of the rudiments of electrical science, or at least of those de- 

 partments of it which have now become almost a part of ever)--day 

 life, is given in language devoid of those technicalities which are 



