518 Scientific Intelligence, 



the spring and placed on the guard-plate wires. On the top of 

 the disc is a tube, in electrical connection with the disc, and 

 containing mercury. The earth-plate is at the position it has 

 when we are measuring potential. The spring is so stretched 

 by a weight that the straight end of its wire dips into the 

 mercury in the tube on the mica-disc, and the apparatus is 

 charged to the same potential it has when we are making a 

 measure of that potential. We now ascertain the weight 

 required to stretch the spring to the same extent it was stretched 

 in the previous experiment. The difference in weight required 

 in the two experiments gives the repulsive action of the elec- 

 tricity on the spring. This correction, however, is not precise, 

 for the wire at the end of spring is slightly pushed upward by. 

 the mutual action of the electrified wire and mercury. 

 Stevens Institute of Technology, Hohoken, N. J. 



SCIENTIFIC INTELLIGENCE. 



I. Chemistry and Physics. 



1. On the Emission- spectrum of Ammonia. — Magnanini has 

 examined the spectrum given by the flame of ammonia when 

 burning in oxygen gas, and has given in a table the wave-lengths, 

 intensities and peculiarities of the lines and bands existing in the 

 region from wave-length 6666 to 4492. The spectrum of am- 

 monia obtained in this way, is much richer and more complex 

 than that obtained by means of the electric spark. On compar- 

 ing the spectrum of burning ammonia with the spectra of ethyl- 

 amine and trimethylamine obtained in the same way with suita- 

 ble access of oxygen, it is easy to recognize in the latter besides 

 Swan's spectrum of the burning gaseous organic compounds, the 

 ammonia spectrum also, though its intensity is feeble. A com- 

 parison of the ammonia spectrum with the spectrum of hydrogen 

 of the second order, shows that a large number of lines in both 

 spectra coincide exactly so far as position goes, but do not agree 

 either in intensity or in appearance otherwise. Whether this 

 coincidence is real or only apparent, resulting from insufficient 

 dispersion, must be determined by further observations. — Zeitschr. 

 Phys. Chem., iv, 435; Ber. JSerl. Chem. Ges., xxiii, (Ref.) 171, 

 March, 1890. g. f. r 



2. On the Absorption-spectrum of Nitrosyl Chloride. — The 

 absorption- spectrum of gaseous nitrosyl chloride, prepared by 

 acting on sodium nitrite with phosphoric chloride in excess, has 

 also been examined by Magna nini. The chloride was contained 

 in a glass tube 49 cm long, so blown at the ends as to give nearly 

 plane and parallel surfaces. The spectrum resembles closely that 

 of the liquid chloride, being a band spectrum, not broken up into 

 lines. It consists of three bands in the red, of which the middle 



