174 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1964 



Cerenkov light resulting from charged-p article showers in the atmos- 

 phere. One possible origin of these showers is extraterrestrial gamma 

 radiation. In the experiment an increase in the number of showers as 

 a source transits the sensitive cone of the mirror would indicate the 

 emission of gamma radiation by the source. In preliminary trials 

 Oerenkov light was detected, and results indicate that this device 

 should provide the most sensitive detector thus far in the search for 

 gamma radiation. The mirror system is part of the solar furnace at 

 the U.S. Army Laboratories, Natick, Mass. The Army has provided 

 use of the instrument and technicians during these experiments. 



The feasibility of using a spark chamber in conjunction with a tele- 

 vision recording system to detect primary gamma rays was exhibited 

 in the laboratory, and a high-altitude balloon experiment using this 

 detector is in preparation. A series of spark chambers was con- 

 structed and evaluated, and a final design was chosen. A television 

 camera (vidicon) was used to observe spark patterns of cosmic-ray 

 particles in the chambers. The vidicon picture was recorded on 

 16 mm film by a kinescope recorder and also transmitted by radio 

 and recorded. In its ultimate form, this instrumentation can be 

 adapted for satellite use to measure the flux of primary gamma rays 

 and to determine their arrival direction and energy. 



Dr. Comerf ord and Dr. Fazio are using laboratory X-ray apparatus 

 to evaluate techniques such as reflection and scattering for the collec- 

 tion and detection of radiation from distant sources and to aid in the 

 design and construction of devices to implement these techniques. 

 Currently, the aim is not to map the sky, but to look carefully at dis- 

 crete sources in the hope of resolving some of the uncertainties about 

 their nature. 



Returning to the less exotic but ever- important visible portion of 

 the spectrum, Drs. Wright and Hodge have completed the Atlas of 

 the Large Magellanic Cloud. Heretofore it has been the custom for 

 scientists who have identified and studied certain objects in the Large 

 Magellanic Clouds to publish identifications in the form of coordi- 

 nates on one of three different coordinate systems. The experience 

 of most scientists with this method of identification has been very 

 unsatisfactory, as the coordinates are inadequate, especially for stellar 

 objects. Ambiguity arises because of the crowded nature of the star 

 fields and the difficulty of establishing the coordinate systems on dif- 

 ferent plates with different scales and distortions. A further hin- 

 drance to progress in the study of the Magellanic Clouds is the lack 

 of any central source of information on objects that have been iden- 

 tified and studied. There have been much confusion and duplication 

 in identification of variable stars, star clusters, and emission regions. 



See footnotes, p. 177. 



