July 19, 1921 proceedings: philosophical society 313 



tration of acid in the solution in which the lead is placed. Practically all 

 the impurities which are found in lead are lodged between the grains. The 

 preferential attack by the corroding agent for these impurities and perhaps 

 also for the "amorphous intercrystalline cement" accounts for the brittleness 

 produced. Investigation showed that specimens of exceptionally pure lead 

 (99.993 per cent), when immersed for 24 days in a neutral solution of lead 

 acetate, became appreciably embrittled by the formation of minute inter- 

 crystalline fissures. No evidence of the existence of an allotropic form of 

 lead similar to gray tin could be obtained. H. S. R. 



CHEMICAL TECHNOLOGY. — Inks — their composition, manufacture, and 

 methods of testing. Bur. Standards Circular 95. Pp. 24. 1920. 



The composition and manufacture are discussed only briefly, but the 

 methods of testing which are in use at the Bureau of Standards are given in 

 sufficient detail to enable any chemist to use them. After a brief introduction 

 on the history of ink, there are discussions of writing and copying inks, ink 

 tablets and powders, marking, cancelling, stamping, duplicating, and sym- 

 pathetic inks. The methods used for the laboratory examination of all but 

 the last of these kinds of ink are next taken up. The circular closes with a 

 short bibliography. 



RADIOTELEGRAPHY. — Principles of radio transmission and reception 

 with antenna and coil aerials. J. H. Bellinger. Bur. Standards Sci. 

 Paper 354. Pp. 63, figs. 17. 1919. 



Coil aerials are coming to replace the large antennas in radio work. It is 

 found that the coil aerial is particularly desirable for communication on short 

 wave-lengths. A coil aerial is as powerful as an antenna only when its di- 

 mensions approach those of the antenna. For other reasons, however, a 

 small coil aerial is in many cases as effective as a large antenna. An advan- 

 tageous type of radio aerial is a condenser consisting of two large metal plates. 

 This type of aerial has many of the advantages of the coil aerial. The funda- 

 mental principles of design of aerials are given in this paper. On the basis 

 of this work the actual functioning of any type of radio aerial can be deter- 

 mined either from measurements made upon the aerials or from actual trans- 

 mission experiments. J. H. D. 



PROCEEDINGS OF THE ACADEMY AND AFFILIATED 



SOCIETIES 



PHILOSOPHICAL SOCIETY 



848th meeting 



The 848th meeting was held in the Assembly Hall of the Cosmos Club on 

 March 12, 1921. It was called to order by President Faris, with 43 persons 

 present. The program was as follows : 



T. S. Sligh, Jr: Recent modifications in resistance thermometer construction. 

 (illustrated.) 



A resume of some of the more important phases of resistance thermometry 

 led up to a brief discussion of present practice at the Bureau of Standards 

 regarding the construction of resistance thermometers. 



The most important points regarding present practice including recent 

 modifications are: (1) The use of the potential terminal type of thermometer 

 with Wheatstone bridge. (2) Thermometer leads made of 12 strands of 

 No. 28 copper wire instead of the fine flexible strand previously used. (3) 



