468 



SCIENCE. 



[Vol. VII., No. 172 



8 inches high. This acted as a calorimeter, the 

 amount of water required to charge it being 1.76 

 pints. In order to charge the explosion-cylinder, 

 it is first filled with mercury, which is allowed to 

 run out, the explosive mixture of air and gas tak- 

 ing its place. The explcsion was caused by an 

 electric current passing through the wire in the 

 top cover. The result of a large number of ex- 

 periments led to the conclusion that the average 

 calorific power of well-purified illuminating-gas, 

 as generally stipulated for by the concessions of 

 French gas companies, is about 5,200 calories per 

 cubic metre. This is equal to 584 British units 

 per cubic foot. The standard of 6,000 calories, 

 hitherto generally accepted, would therefore be 

 too high. M. Witz's experiments more nearly ac- 

 cord with those recently made by Mr. Dugald 

 Clerk, who estimated 504,888 and 489,268 foot- 

 pounds per cubic foot as the mechanical equiva- 

 lents of Manchester and London gas. This would 

 correspond to 5,640 and 5,372 calorie's per cubic 

 metre. M. Witz found that the calorific power 

 of gas supplied from the same works varied con- 

 siderably, at different seasons of the year ran- 

 ging between 4,719 and 5,425 calories ; but the 

 average of tests showed that the difference between 

 the gas supplied by various works was not great. 

 The purification of the gas reduces the calorific 

 power by more than 5 per cent. The gas pro- 

 duced during the last hour of a charge is inferior 

 in heating-power to that obtained during the first 

 hour. The heating-power of gas may be increased 

 77 per cent by carburation ; but the gasoline em- 

 ployed becomes rapidly less volatile, and, when 

 reduced to one-fourth its volume, its enriching- 

 power is only 34 per cent. The details of the ex- 

 periments, which appear to have been made with 

 every precaution to insure accuracy, have been 

 given in the Annates de chimie et de physique for 

 1885, and are quoted in the abstracts of foreign 

 papers of the Institution of civil engineers. 



RE MS EN'S INTRODUCTION TO THE STUDY 

 OE CHEMISTRY. 

 The difficulty encountered by those who de- 

 sire to have science which is true science taught 

 in the high schools and academies of this country 

 has been the lack of good teachers and of suitable 

 books. Gradually, however, the books are ap- 

 pearing. Such volumes as those of Gray on bot- 

 any, Ghiyot on physical geography, Dana on 

 elementary geology, Martin on physiology, and 

 others which we might name, are excellent ex- 

 amples of the skill with which men of ac- 



hitroflticlion to the stufly of chemistry. By IitA IiEMf-KN 

 New York, Holt, 1886. 12°. 



knowledged distinction as scientific men have 

 prepared text-books adapted to youth in their 

 teens. The influence of such books is to awaken 

 a love of the observation of nature, and to show 

 the scholar how, from simple phenomena, he may 

 proceed to those which are difficult and complex. 

 The improved condition of American school-books 

 is sure to have a lasting effect upon the future 

 citizens of this country. Already the increasing 

 love of scientific studies and pursuits is mani- 

 fested in a hundred ways. 



Professor Remsen has now prepared a chemis- 

 try which is intended for those who are beginning 

 the study. No one will question his learning or 

 his experience. For many years his daily round 

 of the laboratory has made him familiar with the 

 perplexities and difficulties which are encountered 

 by students of every grade, — the bright and the 

 dull, the immature and the adult. It sounds 

 paradoxical to hear him declare at the beginning 

 of his work, that, in face of the serious difficulties 

 which lie in the way of a purely scientific treat- 

 ment of chemistry, he thinks it possible to treat 

 the subject more scientifically than is customary, 

 and thus to make it easier of comprehension. 



He therefore lays down as his guiding principle 

 a desire to develop a scientific habit of thought ; 

 and this cannot be accomplished either by hap- 

 hazard, and disconnected experimenting, or by 

 considering the profoundest theories before the 

 student is fitted to comprehend them. The proper 

 course is to begin with an orderly sequence of 

 laboratory lessons, to be performed, if possible, by 

 every pupil for himself, and, if this is not possible, 

 then by the teacher in the presence of a very 

 small class, — not more than ten or a dozen per- 

 sons. 



This volume is therefore prepared as a manual 

 for the laboratory of beginners. The cost of the 

 requisite apparatus is not large, and is quite with- 

 in the allowances of all superior schools, either 

 for girls or boys. The beginning of the course is 

 very easy ; but it soon grows harder, and requires 

 for its conduct a teacher who has himself been 

 trained in laboratory methods. The self-taught 

 chemist will be a very awkward guide. Such an 

 instructor will find his work made delightful by 

 the orderly, progressive steps which are marked 

 out for the class to follow. At frequent inter \ a Is 

 questions are interposed which the student him- 

 self must answer from his own observation and 

 reading. Enough information is given to make 

 his investigations easy and profitable, not enough 

 to stifle independent thought. The author's doc- 

 trine is that a badly performed experiment is as 

 objectionable as a bad recitation or a badly writ- 

 ten exercise. 



