16 



SCIENCE 



[N. S. Vol. XLVII. No. 1201 



their absorption and secondary emission by solid 

 substances. He showed that secondary emission of 

 X-rays was of two varieties. In one of these the 

 X-rays are scattered, without change of quality. 

 The scattered rays were shown by examining ter- 

 tiary emission to be polarized, and this was a 

 fundamental result for the classification of X-rays 

 with ordinary radiation, at that time doubtful. 

 Professor Barkla's other kind of secondary emis- 

 sion is characteristic of the secondary radiator, 

 and is accompanied by selective absorption of the 

 primary rays. He showed that each chemical ele- 

 ment emitted more than one definite kind of sec- 

 ondary fluorescent radiation. Concentrating at- 

 tention on, say, the less penetrating kind, it was 

 found to vary in quality by definite steps with 

 the atomic weight of the secondary radiator. 



REPORT OF THE YEAR'S WORK AT THE U. S. 

 NAVAL OBSERVATORY 



In his annual report to the Bureau of Navi- 

 gation, Eear Admiral Howard, United States 

 Navy, retired, superintendent of the Naval 

 Observatory, says in part: 



The time signals were sent out twice daily dur- 

 ing the year, at noon and 10 p.m., seventy-fifth 

 meridian time, both by land lines and by radio, 

 through the operating relay at Eadio, Va. The 

 improvements mentioned in the last annual report 

 have been completed and put in operation. The 

 accuracy of the radio time signals, which can be 

 picked up anywhere in the north Atlantic, has 

 made it possible to reduce to one the allowance of 

 chronometers for vessels of the Navy operating 

 along the Atlantic coast. 



The Naval Observatory has continued the policy 

 of encouraging suggestions and developments of 

 methods and instruments for navigation, partic- 

 ularly for submarines and aircraft. 



The nautical-instrument repair shop has con- 

 tinued to prove economical in time and expense as 

 compared with the previous system of having this 

 work done by contract. 



Owing to the great increase in ships of the Navy 

 and the lack of receipt of materials and nautical 

 instruments from abroad and the shortage of 

 skilled labor in this country, especially in the 

 manufacture of instruments and chronometers, the 

 question of supply of instruments for navigation, 

 especially chronometers, is becoming a matter of 

 very serious proportions. The increased demand 

 for the gyro-compass and the instruments attached 

 to it is taxing the capacity of the only factory in 



this country which is able to manufacture this in- 

 strument. 



Congress did not provide any addition to the 

 clerical force, and it is earnestly recommended 

 that the additional clerks which will be requested 

 in the estimates to be submitted by the superin- 

 tendent for the next fiscal year be approved and 

 Congress urged to allow the same. 



The scientific personnel has met twice each 

 month, except during the summer, for the discus- 

 sion of current astronomical topics and reading of 

 papers by its members and scientists. 



The astronomical work of this institution is now 

 even more important than usual, owing to the Euro- 

 pean observatories losing many skilled observers 

 due to the war. 



Under the head of Aviation instruments and 

 equipment, the report says : 



As noted in the last annual report, the year 

 started without any instruments or equipment for 

 aviation, under the cognizance of the Bureau of 

 Navigation, having been standardized. 



Sets of clothing as used in the British and 

 Prench aviation services were inspected at the ob- 

 servatory and at the aeronautic station at Pensa- 

 eola, as well as sets manufactured by American 

 firms. A board was appointed at Pensacola to 

 specify a standard equipment and their report has 

 been approved. The Bureau of Supplies and Ac- 

 counts now has specifications for standard articles 

 of clothing and personal equipment. 



THE ENLISTMENT IN ENGINEER RESERVE 



CORPS OF TECHNICAL STUDENTS 



PENDING COMPLETION OF 



STUDIES 



With the approval of the Secretary of War, 

 Major General W. M. Black, chief of engi- 

 neers, has promulgated regulations governing 

 the creation of an Engineer Enlisted Eeserve 

 Corps, in which may be enrolled, pending com- 

 pletion of their studies, students of recognized 

 technical schools. The announcement reads : 



Under such regulations as the Chief of Engineers 

 may prescribe a proportion of the students, as 

 named by the school faculty, pursuing an engineer- 

 ing course in one of the approved technical engi- 

 neering schools listed in the War Department, may 

 enlist in the Enlisted Reserve Corps of the Engi- 

 neer Department, and thereafter, upon presenta- 

 tion by the registrant to his local board of a cer- 

 tificate of enlistment, such certificate shall be filed 

 with the questionnaire and the registrant shall be 



