abstracts: meteorology and electricity 153 



from the first arrangement of the temperatures. In connection with 

 the second arrangement of temperatures and the wind directions, are 

 some remarks upon the dynamics of the lower strata of the atmosphere 

 over high and low pressure areas. \\\ R, B. 



METEOROLOGY.— Free air data at Mmrnt Weather for January, 

 February and March, 1911. Wm. R. Blair. Bulletin Mount 

 Weather Observatory, 4:65-102. 1911. 



Eighty-six ascensions were made at Mount Weather in these three 

 months, 83 by means of kites and 3 by means of captive balloons. The 

 average altitude reached was 2840 meters above sea level. Obervations 

 were made of air pressure, air temperature and wind direction. The 

 data in detail are published in tabular form. The temperature and wind 

 direction aloft are graphically summarized in six Charts, and the surface 

 temperatures at Mount Weather and at the two valley stations, Trapp 

 and Audle} T , in three figures. W. R. B. 



ELECTRICITY. — A comparison of American direct-current switch- 

 board voltmeters and ammeters. T. T. Fitch and C. J. Huber. 

 Bulletin Bureau of Standards 7:407-422. 1911. 



This paper is an analysis of the various factors of performance and 

 details of construction of direct-current switchboard voltmeters and 

 ammeters. All American makers of standard sizes of such instruments 

 were given an opportunity to submit samples. 



The voltmeters all showed maximum errors of calibration less than one 

 per cent of full scale reading, while the ammeters showed maximum 

 errors of from two to six per cent. The ammeters are mere subject to 

 errors than are voltmeters owing to the necessity of working them on 

 the low electromotive force permissible at the terminals of the shunts. 

 The details of performance and the constants of construction are tabu- 

 lated. 



The general lines of design are very similar in all the instrument-, 

 which may be taken as typical not only of American, but also of Euro- 

 pean direct-current practice. The most decided departure from type 

 is in the use of the single air gap in the instruments of one maker. Fur- 

 ther improvements in direct-current switchboard instruments are to 

 be looked for mainly in the refinement of details of design and construc- 

 tion. T. T. F. 



