160 BELL SYSTEM TECHNICAL JOURNAL 



sun. These facts lead to the conclusion that the direction of arrival 

 of these waves is fixed in space; i.e., that the waves come from some 

 source outside the solar system. Although the right ascension of this 

 source can be determined from the data with considerable accuracy, 

 the error not being greater than ± 7.5 degrees, the limitations of the 

 apparatus and the errors that might be caused by the ionized layers 

 of the earth's atmosphere and by attenuation of the waves in passing 

 over the surface of the earth are such that the declination of the 

 source can be determined only approximately. Thus the value 

 obtained might be in error by as much as ± 30 degrees. 



The data give for the coordinates of the region from which the 

 waves seem to come a right ascension of 18 hours and a declination of 

 — 10 degrees. 



A Precision, High Power Metallo graphic Apparatus.'^ Francis F. 

 Lucas. In 1927 the design of an advanced type of metallographic 

 apparatus became of interest. Preliminary designs were prepared and 

 discussed at a conference in Jena, Germany, with the scientific staff 

 of Carl Zeiss. The Zeiss works was commissioned to construct the 

 apparatus. The work was directed by Professor A. Kohler, an out- 

 standing authority on the optics of the microscope, head of the mikro- 

 department of the Zeiss works, and Professor Walter Bauersfeld, a 

 director of the Zeiss Foundation and inventor of the Planetarium. 



In this paper the author discusses the considerations which led to 

 the design and describes the construction of the apparatus. It is the 

 largest and the most powerful metallurgical microscope ever con- 

 structed. Capable of yielding crisp, brilliant images at magnifications 

 of 4000 to 6000 diameters, the design required great mechanical 

 stability, freedom from creep, absolute freedom from outside dis- 

 turbances, the means to illuminate the specimen with light of any 

 selected wave-length or group of wave-lengths within the visible 

 spectrum and the highest order of achievement in optical equipment. 



^ Published in abridged form in Melal Progress, October, 1933. 



