Fkhri'ary 22, 1895.] 



SCIENCE. 



215 



of the second half of the nineteenth cen- 

 tury. 



A. S. Packakd. 



Browx University. 



Heat ; Light; Elementanj Text-Bo()k>', Theoreti- 

 cal and Practical for Schools and College.': : 

 By E. T. Glazebrook. 12 mo., about 

 220 pages each. New York, MacmiUan 

 & Co. Price $1.00. 



These are recent volumes in the series of 

 Cambridge Natural Science Manuals. 



All American physicists are familiar with 

 the previous excellent products of Mr. 

 Glazebrook "s pen in the line of text-books 

 for laboratory and class-i-oom, and will be 

 interested in this new series which is in- 

 tended to fill a place quite different from 

 that for which his previous works were pre- 

 pared. They are less extensive and more 

 elementary. According to the author, they 

 represent what has for some time consti- 

 tuted a practical course for medical students 

 .in the Cavendish laboratorj\ There has 

 been much discussion, and there will con- 

 tinue to be much discussion for some time 

 to come, as to the proper sequence of labor- 

 atory, text-book and lecture instruction in 

 elementary physics. In the Cavendish lab- 

 oratory the system adopted for this course, 

 at least, seems to be that the instructor 

 first presents a portion of the subject in the 

 form of a lecture in which he illustrates, by 

 the use of simple apparatus, and explains 

 the theory of the experiments, deriving 

 principles and numerical results, as far as 

 possible, from the residts of experiments 

 actually performed. The members of the 

 class then make the experiments, singly or 

 in pairs, or occasionally in large groups, 

 using the same, or similar, apparatus. 

 The volumes contain descriptions of experi- 

 ments and also theoretical principles and 

 deductions, so that they constitute at once 

 text-book and laboi-atory hand-book. At 

 intervals througliout the work there will 

 be found well selected coirections of prob- 



lems and examples, and a good set of ex- 

 amination questions at the end. The ap- 

 paratus described is usually simple, and 

 most of it could be made with simph' ma- 

 terials by one having some technical skill 

 of the right sort. 



It is hardly necessary to say that the the- 

 oretical discussions and presentation of prin- 

 ciples are, for the most part, clear and clean 

 as far as they go. 



In the ' Heat,' the first chapter has to do 

 with its nature, and its relation to work or 

 energy is conciselj' but clearly stated. In 

 the second chapter the treatment of temper- 

 ature and its measurement is unusually 

 satisfactoiy, considering the limitations to 

 which the whole work is subjected. It is to 

 be regretted, however, that there is no men- 

 tion of the hj'drogen scale, since so many of 

 the most important temperature measure- 

 ments now depend upon it. Calorimetrj' is 

 discussed quite thoroughly, with many prac- 

 tical illustrations, and in the chapters de- 

 voted to expansion several neat suggestions 

 as to methods will be found. In the refer- 

 ence to the necessity for ' compensating ' the 

 eflfect of temperature on the balance wheel 

 of a watch, it is erroneously implied that the 

 principal reason for this grows out of the 

 change in the dimensions, and consequently 

 moment of inertia of the wheel due to change 

 in temperature, while, as a matter of fact, 

 it is the temperature change of the modulus 

 of elasticity of the ' hair ' or balance spring 

 which makes nearly all the trouble. The 

 volume ends with a brief but good chapter 

 on the mechanical equivalent of heat. 



In the volume on ' Light,' the geometrical 

 treatment is used exclusively. There is a 

 single brief reference to the physical nature 

 of light, which is so thoroughly discussed 

 in the author's volume on ' Physical Optics ' 

 published some years ago, but in the book 

 under consideration the rectilinear propa- 

 gation of a ' raj' ' is assumed and made the 

 basis of the whole discussion . The chapters 



