178 THE AMERICAN MONTHLY [Jun 



V depth of the thread bein<^ rounded off at the top of the 

 thread and one sixth of the thread being- rounded off at the 

 bottom of the thread. The pitch of the screw is, 36 to 

 the inch ; length of thread on object-glass, 0*125 inch; plain 

 fitting above thread of object-glass, 0*15 inch long, to be 

 about the size of the bottom of male thread ; length of 

 thread of nose-piece on the lower end of the microscope- 

 tube not less than 0"125 inch ; diameter the object-glass 

 screw at the bottom of the screw, 0.7626 inch ; diameter of 

 the nose-piece screw at the bottom of the thread, 0.8 inch. 

 See Jour. Roy. Mic. Soc, Aug., 1896; Proc. Amer. Mic. 

 Soc; 1884, 1886, 1893. It is remarkable that no description 

 of the Society Screw is to be found in "Carpenter on the 

 Microscope." 



Wanted. — Earth containg diatoms from Redondo Beach 

 for a European subscriber who offers cash, or, in exchange, 

 Hungarian diatomaceous material from St. Peter. C. W. S. 



New Publications. 



Acetylene is the title and subject of a profusely illus- 

 trated work of some five hundred pages which the Mac- 

 millan Company will publish at an early date. The history 

 of the origin, properties, and application of this gas is very 

 fully treated, anil the cuts, of which there are upwards of 

 one hundred and lifty, add greatly to the descriptive value 

 of the text. 



Plants, a Text Book of Botany, in two parts. Part I, 

 Plant Relations. Figures 206, pp, 264. Part II, Plant 

 Structures, Second Book of Botan}', Figures 289, pp. 384. 

 D. Appleton & Co., 1900. 



Prof. J. M. Coulter, Head Professor of Botany, Univer- 

 sity of Chicago, 111. is the author of an admirable text-book 

 of botany which is intended as an introduction to the 

 science. The two parts have been prepared as independ- 

 ent volumes for the reason that some schools cannot give 

 but a half-year to botany. The subject of each part cov- 

 ers one-half year. The volume is intended as introduction 

 to the study of botany. The author has certainly succeed- 



