612 



^ A Text-book of Astronomy. 



SCIENCE. 



[N. S. Vol. XIV. No. 355. 



By George C. 

 CoMSTOCK, Director of the Washburn Observ- 

 atory and Professor of Astronomy in the 

 University of Wisconsin. New York, D. 

 Appleton and Company. Cloth. Pp. 391. 

 Price, $1.30. 



Written in simple, clear and concise lan- 

 guage, illustrated by appropriate and well-con- 

 structed figures, made interesting by apt and 

 homely comparisons and useful by numerous 

 and well-chosen exercises, this book forms a 

 welcome addition to the list of elementary text- 

 books of astronomy. Professor Comstock has 

 written a new book and has not merely rear- 

 ranged the material of earlier ones. His pur- 

 pose is clearly outlined in the first paragraph of 

 the preface : " The present work is not a com- 

 pendium of astronomy or an outline of popular 

 reading in that science. It has been prepared 

 as a text-book, and the author has purposely 

 omitted from it much matter interesting as well 

 as important to a complete view of the science, 

 and has endeavored to concentrate attention 

 upon those parts of the subject that possess 

 special educational value. From this point of 

 view, matter which permits of experimental 

 treatment with simple apparatus is of peculiar 

 value and is given a prominence in the text be- 

 yond its just due in a well-balanced exposition 

 of the elements of astronomy, while topics, such 

 as the results of spectrum analysis, which de- 

 pend upon elaborate apparatus, are in the ex- 

 perimental part of the work accorded much less 

 space than their intrinsic importance would 

 justify." 



Inspection of the table of contents shows that 

 the author has departed widely from the con- 

 ventional methods of treating the elements of 

 the subject, especially in the first six and the 

 eighth chapters. The special features of the book 

 are numerous questions scattered throughout 

 the text, to teach the student to think and con- 

 struct as well as to read and assimilate ; and 

 many exercises, in the nature of laboratory 

 work, all to be performed with simple appara- 

 tus, easily constructed by the students them- 

 selves. In these exercises the students obtain 

 practice in the three fundamental processes of 

 all practical astronomy, the measurement of 

 time, angle and distance. Although the exer- 



cises are numerous, still the author has not ex- 

 hausted the list and might with profit have 

 given more. 



It would have been well, if possible, to so 

 arrange the material that the exercises, which 

 all fall in the first five chapters, would be more 

 distributed. It is not necessary, of course, 

 that the teacher present the material in just 

 the order given, but the facts are that the large 

 majority of teachers will present it in that 

 way. The author has, apparently, purposely 

 avoided all reference to the Nautical Almanac 

 and American Ephemeris. The wisdom of this 

 is open to question. While it is unnecessary 

 and certainly unwise to introduce the Ephem- 

 eris at first and thus make the student de- 

 pendent upon it, still I think it equally unwise 

 to totally exclude it. An explanation of the 

 Ephemeris and a few exercises which demand 

 its use should, I think, be included in the 

 most elementary course in practical astronomy. 

 Any school in which astronomy is taught can 

 surely afford to buy one of these books each 

 year, and any person capable of teaching the 

 subject should be able to use the book intelli- 

 gently. 



Many bits of good advice are given in con- 

 nection with the exercises. On page 3, for 

 instance, in connection with a measurement to 

 be made, we find : " But perfection can seldom 

 be attained, and one of the first lessons to be 

 learned in any science which deals with meas- 

 urement is that however careful we may be in 

 our work, some minute error will cling to it 

 and our results can be only approximately true. 

 This, however, should not be taken as an ex- 

 cuse for careless work, but rather as a stimulus 

 to extra effort in order that the unavoidable 

 errors may be made as small as possible." 



A point to be commended is the use of the 

 metric system throughout the exercises. In 

 the descriptive parts of the text, however, the 

 author retains the English units. Perhaps it is 

 best to break away gradually, but I believe no 

 criticism would have been offered if the metric 

 system had been used throughout. 



The illustrations and figures of the book are 

 well chosen and the student should learn some- 

 thing from each. Very few, if any, have been 

 inserted for pictorial effect. Among the figures 



