:o2 



THE POPULAR SCIENCE MONTHLY. 



engine and a refrigerator at the absolute 

 .zero of temperature, we might convert the 

 whole of the heat which escapes from the 

 body into mechanical work." On pages 99 

 and 100 we have a similar carelessness, in the 

 use of the term strain : this is defined on 

 page 99 to mean " the alteration of form of 

 any body ; " while on page 100 he speaks of 

 the " product of the strain into the average 

 value of the stress," i. e., of the product of 

 a force into a change in shape, which of 

 course is a misnomer, and could be correct- 

 ed by interpolating the phrase in any di- 

 rection after " strain." 



There are but few of even such errors 

 as these, and we must welcome the book as 

 a most valuable one, in which the golden 

 mean between too great simplicity and too 

 great difficulty is admirably kept ; and in 

 the name of the ordinary student we are 

 thankful to Prof. Maxwell for his most 

 admirable essay. E. S. H. 



How Plants behave. By Asa Gray. New 

 York : Ivison, Blakeman & Taylor. 



Fourteen years ago, Prof. Gray pub- 

 lished a little school-book, entitled "How 

 Plants grow," which was designed as a 

 first step, for young people and common 

 schools, of his excellent series of botanical 

 text-books. The present volume of forty- 

 six pages, " How Plants behave," is Part 

 II., or a continuation of " How Plants grow," 

 and is devoted to a description of certain 

 remarkable actions and effects in the vege- 

 table kingdom which are open to familiar 

 inspection. The author's object in the 

 preparation of these little works is thus 

 stated in his preface : 



" That young people, that all students, 

 indeed, should be taught to observe, and 

 should study Nature at sight, is a trite re- 

 mark of the day. But it is only when they 

 are using the mind's eye as well, and raising 

 their conceptions to the relations and 

 adaptations of things, that they are either 

 learning science or "receiving the full educa- 

 tional benefit of such a study as Botany or 

 any other department of Natural History. 



" There is a study of plants and flowers 

 admirably adapted, while exciting a lively 

 curiosity, to stimulate both observation and 

 thought, to which I have long wished to 

 introduce pupils of an early age. The time 



has now arrived in which I may make the 

 attempt, and may ask young people to con- 

 sider not only, 'How Plants grow,' but 

 how plants act in certain important re- 

 spects, easy to be observed everywhere 

 open to observation, but (like other common 

 things and common doings) very seldom 

 seen or attended to. This little treatise, 

 designed to open the way for the young 

 student into this new, and, I trust, attractive 

 field, may be regarded as a supplement to 

 the now well-known book, the title of which 

 is cited at the beginning of this prefatory 

 note. If my expectations are fulfilled, it 

 will add some very interesting chapters to 

 the popular history of plant-life. 



" Although written with a view to ele- 

 mentary instruction, and therefore with all 

 practicable plainness, the subjects here 

 presented are likely to be as novel, and 

 perhaps as interesting, to older as to young 

 readers." 



Prof. Gray has well succeeded in his 

 purpose, and the pages of his little book are 

 full of interest to all who care for the curi- 

 osities of the vegetable world. His volume 

 is divided into three chapters. The first 

 shows how plants move and climb and take 

 positions ; the second tells how plants em- 

 ploy insects to work for them; and the 

 third describes how certain plants capture 

 insects. Among all the surprising effects 

 presented by natural objects, none are more 

 curiously interesting than the habits and 

 adaptations of vegetable structures, and 

 Prof. Gray tells the story in his own clear 

 and graphic way. The pages of his little 

 book are full of pleasant information, and 

 cannot fail to be instructive ; and, if the 

 pupils are attracted to go beyond its pages 

 to examine for themselves the structures 

 and actions described, the experience will 

 be invaluable as a cultivation of the observ- 

 ing powers. 



MISCELLANY. 



Death of Dr. Stimpson. In the recent 

 death of Dr. William Stimpson, secretary of 

 the Chicago Academy of Sciences, American 

 science has suffered an irreparable loss. He 

 was born near Boston, February 14, 1832, 

 and was drawn by a strong impulse to the 

 study of science in his boyhood. Hia 



