Febkuart 17, 1922] 



SCIENCE 



183 



tensive relations insects bear to many human 

 and plant diseases. The activities of insects 

 as parasites and as carriers of disease or- 

 ganisms are, however, noted here and there 

 throughout the text in. appropriate connection 

 with the species concerned. 



The remaining pages of the book are de- 

 voted to a discussion of the characteristics of 

 the dilferent orders of insects with an account 

 of the life histories, habits, and control of a 

 well-selected list of common, representative, 

 and mostly economic species of each order. 

 The author uses commendable and conservative 

 judgment in recognizing and discussing but 

 twenty-four orders with a brief mention of an 

 additional one, the Zoraptera. An economic 

 entomologist often wishes the author had been 

 a little more siaecifie regarding control 

 measures. For example, paradichlorobenzene 

 is briefly mentioned as having "given fair suc- 

 cess recently" in the control of the peach-tree 

 borer. This seems hardly an adequate state- 

 ment in view of the widely successful vise of 

 this substance by the Federal Bureau of En- 

 tomology and by the New Jersey Experiment 

 Station. 



The book is fully illustrated with numerous 

 original photographs and many familiar illus- 

 trations. It is certainly preferable to use good 

 familiar figures in a text-book rather than poor 

 original ones but great pains shovild be taken 

 to reproduce the old figures with distinctness 

 and fidelity. For example, figures 130, 131, 

 135, and 242 have lost much of their original 

 clearness and detail. Moreover one is apt to be 

 momentarily a bit shocked to find an illustra- 

 tion in a dignified text-book with the legend 

 "Samples of Anoplura greatly enlarged" with- 

 out any attempt to give the reader an inkling 

 of the species figured. These, however, are 

 small matters. 



The book has few typographical eiTors and 

 closes with an excellent index of twelve pages. 

 Altogether the author has written a well bal- 

 anced, well arranged text of applied entomology 

 for the beginning student and many teachers 

 will find it very useful with their classes. 



Glenn W. Heerick 

 Cornell Univeksity 



SPECIAL ARTICLES 



HIGH SPEED HIGH VACUA MERCURY 



VAPOR PUMPS 



The writer has on several occasions^ 

 described two types of high speed mercury 

 vapor pumps capable of producing exceedingly 

 high vacua in reasonably short intervals of 

 time and j-et not demanding of the fore pumps 

 pressures less than .01 to .005 mm. of mercury. 

 These mercury vapor piunps were made of 

 pyrex glass and are still in use. 



Since then slight modifications have been 

 introduced which considerably reduce the time 

 required in glass blowing though not altering 

 the speed of either pump or the vacua obtain- 

 able. The two types in modified form are 

 shown in Figures 1 and 2, and are each drawn 

 approximately one sixth full size. In Figure 



DorfeJ Arrjivs /n^'cafe 

 /b//} o^ Mercury. 



High [/acuam 

 t^srcury l<:rpor Pu/Tjp 



1 we have the umbrella type in which the bulb 

 to be exhausted is attached to B, and the sup- 

 porting pump to E. The hot mercurj^ vapor 

 reaches the umbrella P through the large diam- 

 eter thin-walled central delivery tube O. The 

 throat at V is. large and annular (no central 

 dead space) and hence the issuing mercury 

 vapor comes into immediate contact with the 

 outer water cooled walls. This construction 



1 Vliys. 'Rev., II, 9, 311; 12, 492. 



