Febkuart 7, 1913] 



SCIENCE 



223 



The key to tlie families of Diptera is writ- 

 ten by an eminent authority in that group 

 and will doubtless prove one of the most 

 valuable parts of the book. Unfortunately 

 some of the smaller families are omitted. 

 The most serious drawback, so far as the 

 present work is concerned, is the fact that the 

 old and complicated Schinerian system of 

 wing venation nomenclature is used, but no- 

 where explained, the explanatory figures of 

 wings of Diptera, as in the other orders, being 

 lettered by the Comstock-Needham system. 

 The wing of Blepharocera is figured, although 

 the Blepharoeeridce are omitted from the keys 

 and the text does not explain that the intri- 

 cate maze of intersecting lines are not veins, 

 but folds in the wing membrane. They will 

 surely puzzle any one who does not appreciate 

 that fact. " Second boscal " cell (bottom of 

 p. 323) is probably a misprint. 



The wings of Hemerobiidae are not ordi- 

 narily opaque, as stated in the table on page 

 307. Only one family of Trichoptera is recog- 

 nized, although all authorities to-day would 

 agree in recognizing more. Only one family 

 of Thysanoptera is recognized, despite the fact 

 that modern authorities recognize two subor- 

 ders and several families. 



In the key to families of Hemiptera the first 

 category is " wingless insects with fleshy un- 

 jointed beak," its alternative is " winged or 

 wingless insects, with a jointed beak," but 

 under the latter is a subheading which pro- 

 vides for wingless insects with the beak want- 

 ing! Further, the beginner would often ex- 

 perience dilficulty in recognizing the jointed 

 character of many Coccid beaks. 



The Aphidffi are differentiated from Aleyro- 

 didse and Coccidse by having " long and slen- 

 der legs and transparent wings," while the two 

 latter are said to have " legs short, wings 

 usually opaque." It is hardly necessary to 

 mention the many legless Coceidffi, as well as 

 the long-legged forms (Orthezia, etc.). 



In the table to Coleoptera the majority of 

 families are omitted altogether, and so are 

 very many in the Lepidoptera. In the dis- 

 cussion of the latter order no mention is made 

 of a division into two suborders Jugatse and 



Frenatse, but the hutterflies and moths are said 

 to form two main divisions of the order. The 

 wing of Hepialus, however, is figured and the 

 jugum noted in the legend. Such an insuffi- 

 cient statement as " subcosta and radius of 

 hind wing connected by a cross-bar " is noted 

 in the characterization of Sphingidse. 



The work closes with chapters on collecting 

 and preserving insects, which will be of great 

 value to the student. 



The book is well printed on good paper and 

 the illustrations, as a rule, come out well; 

 when properly revised, it will make a welcome 

 addition to the rapidly growing list of entomo- 

 logical texts, from which the teacher can 

 choose the one best suited to the needs of his 

 students. 



C. E. Crosby 



Cornell University 



Dynamic Meteorology and Hydrography. 



Part I., Statics. By "V. Bjerknes and J. 



W. Sandstrom. Quarto. Pp. 234. Part 



II., Kinematics. By V. B.tkpknkr, Th. 



Hesselberg and O. Devik. Quarto. Pp. 



175 (with atlas of 60 charts). Carnegie 



Institution, 1911. 



The object of this treatise is to develop 

 practical methods for the systematic study of 

 the pressure, temperature, humidity, density 

 and velocity of the atmosphere. On account 

 of the difficulty of solving the differential 

 equations of a viscous gas the methods are 

 almost entirely graphical, elaborate tables be- 

 ing given that obviate the necessity of even 

 ordinary integration. In Part I. it is assumed 

 that the conditions of equilibrium are ful- 

 filled along every vertical line. From the rec- 

 ords of a balloon sent up with self-registering 

 instruments for pressure, temperature and 

 humidity, it is therefore possible to calculate 

 the pressure and density at different heights. 

 For facility of calculation the authors divide 

 the atmosphere into sheets each about 1,000 

 meters thick, beginning at sea level, and find 

 the average density and temperature of each 

 sheet. To allow for the humidity and still 

 use Boyle's law, as for dry air, a virtual tem- 

 perature is used that is derived from the 



