236 Scientific Intelligence. 



With the second form of apparatus extremely interesting 

 phenomena were obtained with nitrogen, when the pressures 



inside ami outside the silica tube were 155' mm. and 7 mm., 

 respectively. In this case, however, the simple induct ion coil 

 discharge without a condenser gave the best results. P.olh the 

 jet and spark had a reddish-orange color and the jet could be 

 traced for a distance of 5 cm. from the orifice. "The most 

 striking features of this jet, both visually and photographically, 

 are the alternations of light anil comparative darkness which may 

 be seen along its length. Five or six of these can easily be 

 counted, but they become less distinct the farther out we go from 

 the orifice. They remain absolutely steady in position in spite 

 of any irregularity in the working of the induction coil." 

 Strutt shows that the variations in luminous intensity are of 

 purely hydrodynamic origin, changes in density giving rise to 

 corresponding alterations in intrinsic brightness. By using 

 Emden's empirical formula for the wave-length of the periodic 

 structure and extrapolating, a length of 2 mm. is obtained. 

 Strutt 's photographs show that the wave-length is 1.8 mm. 

 Under the circumstances, the agreement may be considered quite 

 satisfactory. The last part of the paper deals with the spectrum 

 of the nitrogen jet. The spectrum consists of the bands known 

 as the first, second, and third positive nitrogen groups. This 

 spectrum is entirely different from that of the "active modifi- 

 cation" of nitrogen. The luminosity of the jet lasts for about 

 1/6000 of a second whereas that of the active modification often 

 persists for several seconds, or even minutes. — Proc. Boy. Soc, 

 94 A, 88, 1917. h. s. u. 



7. Magnetic Tables and Magnetic Charts for 1915; by 

 Daniel L. Hazard. Pp. 256 ; numerous tables, 5 charts. 

 Special Publication No. 44. U. S. Coast and Geodetic Survey. 

 E. Lester Jones, Superintendent. — The introductory chapter 

 (pages 5 to 15) is historical and explanatory. Pages 16 to 

 94 give, in tabular form, the secular change data derived from 

 observations at repeat stations. Secular change tables, that is. 

 tables for reducing the values of the declination, inclination, and 

 horizontal intensity to Jan. 1, 1915, occupy pages 95 to 99. The 

 observed magnetic elements (D, I, H) and the corresponding 

 values reduced to 19150 are tabulated on pages 100 to 226. 

 These tables refer not only to the United States but also to 

 Canada, Mexico, the West Indies, Central America, Colombia, 

 Guiana, Venezuela, the Gulf of Mexico,, the Caribbean Sea, and 

 certain portions of the Atlantic and Pacific Oceans. The rest of 

 the volume comprises tables of the magnetic elements and mag 

 netic components for each degree of latitude and longitude. 

 Five loose charts, each on a scale of 0-9 inch to 100 statute miles, 

 are contained in a pocket attached to the back cover. These 

 give respectively, lines of equal declination and equal annual 



