1>«'.L' rill-: AMKKICAN .MONTH LV [Sopt., 



KDITOHI VL. 



Carborundum. — This new comiioiind is iiKuIr tVoin carlHUi, 

 sand :intl salt, but it is comj)OSC(l of siliron (iU prr ctiit, carbon 

 30, impuritios 1 por cent. Under the microscope it exhibits 

 crystals of :i blue color, but with some of a yellow-green color, 

 some black, and some white. The crysUils are sifted tliroui^h a 

 seive havinj; 2.')W or more meshes to the S(}uare inch but are 

 too large to pass through one having 4(),0(X) meshes to the square 

 inch. The three important characteristics of carborundum are 

 great hardness, infusibility and incombustibility. It will there- 

 fore be used much as an abrasive material and to some extent 

 replace emery. It can be used to cut diamonds. 



'i'hese cr\'stals are rhombohedral. both direct and inver.se. 

 Professor B. W. Frazier of Lehigh, who has examined some 

 crystals, says : "A Hat crystal examined under the microscope 

 in converging polarized light gave the interference figure of a 

 uniaxial mineral, thus confirming the determination of hexago- 

 nal symmetry made by measurements with the goniometer." 



The Secretary of the Carborundum Comjiany, Mr. C. M. 

 Hagen, has kindly favored us with .some specimens of crude 

 material. To a limited nunil)er of subscribers we can mail enough 

 to make a few mounts, and to all our contributors who so desire 

 we .shall take great i)leasure in sending samples. 



A New Illustrated Dictionary of Medicine, Biology, and 

 Collateral Sciences. — Dr. George M. Gould has now about 

 ready an unabridged, exhaustive work of the same class, in 

 which he has already earned a reputation, and upon which he 

 and a corps of able assistants have been iminterruptedly 

 engaged for several years. 



The fr-ature that will attract immediate attention is the large 

 number of fine illustrations that have been included, many of 

 which as, for inst^mce, the series ofover fifty of the bacteria-have 

 been drawn and engraved especially for the work. t]very scien- 

 tific-minded jthysician will also be glad to have defined several 

 thousand commonly used terms in biology, chemistry, etc. 



The chief point, however, upon which the editor relies for the 

 success of his book is the unique epitomization of old and new 



