474 



POPULAR SCIENCE MONTHLY. 



have walked the face of the earth, but | 

 existing whales are the greatest of ani- 

 mals, and the living elephants are 

 larger than the mastodon and compare 

 favorably with the mammoth. The first 

 of the dozen chapters treats of fossils 

 and how they are formed, while the ; 

 last discusses the problem why do ani- . 

 mals become extinct, suggesting some j 

 of the causes which lead to extermina- : 

 tion, and showing that in some in- I 

 stances apparent extinction is in reality 

 evolution, one species passing into • 

 another, so that the race endures while 

 individuals die out; this is well illus- j 

 trated by the chapter devoted to the 

 ancestry of the horse. Reading the 

 riddles of the rocks tells how animals 

 are interpreted by their fossil remains 

 even if it is not possible to reconstruct 

 an animal from a single bone or tell its 

 size and habits from a tooth. Other 

 chapters are devoted to birds of old, { 

 the dinosaurs, feathered giants, the | 

 mammoth and the mastodon, and at the 1 

 end of each chapter is stated where the 

 best examples of the animals described 

 may be seen, while in many instances 

 the size of the largest specimens is i 

 given. The book is illustrated with 

 restorations of extinct animals drawn \ 

 by Mr. C. R. Knight and J. M. j 

 Gleeson, and while these may look a 

 little tame beside some of those that 

 have appeared in the Sunday papers, 

 they are the result of long and careful 

 study and may be regarded as among 

 the most accurate that have been 

 made. 



ENGINEERING. 



A 'Field Manual for Engineeks' 

 by Philetus H. Philbrick (Wiley and 

 Sons ) , treats only of the svirveying work 

 of railroad location and construction, 

 but this is set forth in a thorough and 



interesting manner. No logarithmic 

 tables are given, as is usual in such 

 field-books, the author claiming that 

 ' they are but little used and should not 

 be used at all.' Whatever may be 

 thought of this remarkable statement, 

 it must be said that the twelve pages 

 given on approximate and abridged 

 methods of numerical computations are 

 of great interest and value; if such 

 methods were generally taught to engi- 

 neering students it would certainly 

 prove highly advantageous in enabling 

 them to perform computations with a 

 degree of precision consistent with the 

 given data. 



'Water Filtration Works,' by 

 James H. Fuertes ( Wiley and Sons ) , 

 treats this important topic mainly 

 from the engineering point of view. 

 Both slow filtration by sand beds 

 and rapid filtration by mechanical 

 means with the help of a coagulent are 

 fully described, the methods of clearing 

 and operating being in particular well 

 exemplified by illustrations of the de- 

 tails of plants recently installed. The 

 purification of river waters carrying 

 much suspended matter is discussed in 

 connection with the results of the ex- 

 periments made at Pittsburgh, Cin- 

 cinnati and Louisville. For towns 

 where it is doubtful whether a sand 

 filter bed need be covered the author 

 suggests that a combination of the slow 

 and rapid filtering methods might be 

 made, the former being used in summer 

 and the latter in winter. The book 

 bears evidence of having been prepared 

 with care, and it is a valuable addition 

 to the literature of a subject which con- 

 stantly increases in importance as the 

 public comes more and more to real- 

 ize that the use of pure water dimin- 

 ishes the death rate from zymotic 

 diseases. 



