14^ 



SCIENCE. 



[Vol. XII. No. 294 



that the public demands a much brighter illumination than for- 

 merly, and this increase of illumination has by no means reached a 

 maximum. 



A New Insulating Compoxjnd. — The following, from the 

 Electrical World, is taken from the Chron/qiie Indiistrielle : 

 "The compound is composed of one part of Greek pitch and two 

 parts of burnt plaster by weight, the latter being pure gypsum 

 raised to a high temperature and plunged into water. This mixture, 

 when hot, is a homogeneous viscous paste, and can be applied with 

 a brush or cast in moulds. It is amber-colored, and possesses the 

 insulating properties of ebonite, and can be turned and polished. 

 Its advantage is its endurance of great heat and moisture without 

 injuring its insulating properties." 



Specific Resistance of Mercury. — Since the absolute unit 

 of electrical resistance has been defined in terms of a column of mer- 

 cury of one millimetre cross-section and of a given length, a num- 

 ber of determinations of the specific resistance of mercury have 

 been made. The latest is by Messrs. Glazebrook and Fitzpatrick, 

 and gives for a result that the resistance of a column of mercury 

 one millimetre in cross-section and one metre long is r = 0.95352 

 B. A. units. The other results that have been obtained are — 



• Electric Tramways in Salt-Mines. — In the new Stass- 

 furt mine an electric tramway has been in operation since January, 

 1884. It was built by Siemens & Halske, and was a success from 

 the start. The engine is of 20-horse power, and is placed above 

 ground at the mouth of the shaft. The dynamo is compound 

 wound, and gives about 40 amperes at 300 volts. The current is 

 taken through cables to the tram-line, a distance of 410 metres. The 

 motor is supplied from overhead iron conductors, insulated from 

 the ground. The motor is simply one of the well-known type of 

 Siemens dynamos, placed horizontally on a car to economize space. 

 The dynamo supplies about 20-horse power of energy ; the motor 

 gives about lo-horse power, — an efficiency of only fifty per cent. 

 The weight of the wagons to be drawn is about 2,500 pounds, and 

 there are sixteen in a train. The mean speed is about six miles per 

 hour. This line is not in any way so efficient as those that can be 

 put up to-day, but some figures as to the cost of working are of in- 

 terest, especially as the road has been long enough in operation to 

 allow an accurate estimate to be made. In 1884, 176,196 trucks 

 were handled ; and the working cost, including all items, wages, 

 fuel, etc., with fifteen per cent for interest and depreciation, was 

 lo.i pfennig (about 2i cents) per truck, while the cost before had 

 been 20 pfennig (5 cents). In 1887 the figures are still more favor- 

 able, as the underground electric way had been considerably in- 

 creased. The cost was 8.3 pfennig (about 2 cents) per truck, or 

 12.92 pfennig per kilometre ton, as compared with 34.2 pfennig 

 per kilometre ton by human labor, which the electricity displaced. 

 If the few electric tramways in mines that are now in operation in 

 this country were investigated as to cost, it would be found that 

 their economy is as great as that given above. It is only a question 

 of a few years when mule and man power in mines will be replaced 

 by electric motors. 



Michel Eugene Chevreul, the chemist, entered his hundred 

 and third year on Aug. 30. He is still active, and a few days ago 

 was able to visit the Sanitary Exhibition at the Palace of Industry. 



BOOK-REVIEWS. 



Eclectic Physical Geography. By RuSSELL HiNM.iN. Cincin- 

 nati, Van Antwerp, Bragg, & Co. 12°. %\. 



• " The aim of this book is to indicate briefly what we know or 

 surmise concerning the proximate causes of the more common and 

 familiar phenomena observed at the earth's surface. Even thus 

 restricted, the field of inquiry encroaches to a greater or less extent 

 upon the domains of all the branches of science. Since the study 

 of physical geography precedes that of the sciences in most of our 

 schools, it has been thought advisable to present, in the form of an 

 introductory chapter, a condensed statement of the more important 

 and fundamental scientific conceptions regarding the properties 

 and phenomena of matter and energy, such as inertia, gravitation, 

 cohesion, affinity, and heat, light, magnetism, and electricity." 



This passage, taken from the preface, shows the scope and ob- 

 ject of the volume under review. The different parts of the subject 

 are treated in the order used in all books of this character. Math- 

 ematical geography forms the first part. This is followed by me- 

 teorology, oceanology, geophysics, and biology. The book is illus- 

 trated by many maps, in which the most recent discoveries and 

 researches have been made use of, and which, considering their 

 smallness, are quite satisfactory, and undoubtedly superior to those 

 defacing most American text-books of geography. In a number 

 of maps the author has preferred to omit the system of meridians 

 and parallels ; it seems to us, not to the advantage of these maps. 

 The great number of maps, and the fact that they are copied from 

 the best authorities available, make the book very useful to the stu- 

 dent. The chapters on meteorology and geophysics are the bes'' 

 parts of the book, while in that part treating of the oceans we find 

 many statements that are not entirely in accord with the vie^vs held 

 by the best writers. We particularly object to the method of the 

 author of describing theories advanced by individual authors, but not 

 generally accepted, — for instance, Murray's theory of the origin of 

 deep-water deposits, and Ferrel's theory of ocean-currents, — as firmly 

 established facts. A book of the character of this ' Eclectic Physi- 

 cal Geography,' if giving as much theory as the present one does, 

 ought to give the views of opposing parties, and not favor one to 

 the exclusion of another. In Part IV. the author gives first an 

 outline of the topography of the earth, which is generally not 

 treated in books of this character. After a brief treatise on 

 weather and climate, the forms of life are discussed. It seems to 

 us that the author, in this the last part, does not do full justice to 

 his subject, his treatment being too brief, and his views not quite 

 clear in all respects. Evidently it is his opinion that the principal 

 part of geography consists in the study of geophysics. The book 

 is, on the whole, well adapted to be used in the higher grades of 

 teaching geography, although it might have been better to treat 

 theories less dogmatically. 



The Chemical Analysis of Iron. By Andrew Alexander 

 Blair. Philadelphia, Lippincott. 8". S4- 



In this book Mr. Blair describes those methods of analysis which, 

 in his extended experience, he has found to be of most value to the 

 iron-chemist. The first twenty-two pages of text are devoted to 

 the description of the necessary and most suitable apparatus ; twenty- 

 one pages treat of the re-agents ; then follow detailed methods for 

 the analysis of iron and steel, iron ores, limestone, clay, slags, fire- 

 sand, coal and coke, and furnace gases ; tables to facilitate the 

 calculation of analyses follow ; and the book ends with a very com- 

 plete index. 



The work is well done, the arrangement good, the descriptions 

 clear and to the point, the illustrations excellent. It forms a man- 

 ual which must prove of the greatest assistance to those entering 

 this field of work, while those who are already familiar with this 

 branch of technical analysis will find it a convenient reference- 

 book, and doubtless gain from it a number of valuable suggestions. 



In Fresenius's ' Quantitative Analysis ' (sixth German edition) 

 fifty-two pages of the ' Special Part ' are given to methods for ana- 

 lyzing iron and iron ores, and Bolley's ' Handbuch ' contains seventy- 

 seven pages on the same subject ; but this is, so far as we are 

 aware, the first complete work containing between its covers not 

 only all the best methods for the analysis of all materials directly 



