316 



SCIENCE. 



[N. S. Vol. V. No. 112. 



reflection and absorption. The results indicate 

 distinctly the presence of anomalous dispersion, 

 the critical wave-length being that where the 

 absorption of the quartz becomes complete. 

 The article is an important one in its bearing 

 upon the theories of dispersion and absorption. 



Heat Bays of Great Wave-Length : By H. Ru- 

 bens and E. F. Nichols. Experiments are de- 

 scribed in this paper by which infra-red rays 

 were detected of greater wave-length than any 

 heretofore observed. The longest wave-lengths 

 in the infra-red which had previously been 

 measured were those studied by Paschen in 

 connection with the dispersion of fluorite. 

 These rays had a wave-length of a little less 

 than 10 /i. Messrs. Rubens and Nichols have suc- 

 ceeded in obtaining and measuring rays whose 

 length is 25/;, these rays being obtained by 

 successive reflection from fluorite. It appears 

 that this substance possesses an absorption band 

 in the neighborhood of 25 ,«, which is so intense 

 as to suggest metallic absorption. There re- 

 sults a great increase in the reflecting power of 

 the material in the neighborhood of this wave- 

 length, so that after successive reflection from 

 three surfaces of fluorite the rays that remain 

 are found to consist almost wholly of waves 

 corresponding to this absorption band. The 

 wave-length was determined by means of a 

 wire grating. Similar experiments with quartz 

 led to the detection of waves of about 6.5 /i. 

 Experiments were also tried with rock salt, but 

 the bolometer was not sufficiently sensitive to 

 enable the resulting waves to be measured. 

 The authors intend to continue this work, us- 

 ing the improved radiometer described by Pro- 

 fessor Nichols in the previous paper. 



On the Formation of Lead Sulphate in Alterna- 

 ting Current Electrolysis with Lead Electrodes: 

 By S. Sheldon and M. B. Waterman. The 

 work described in this paper is in part a con- 

 tinuation of the authors' experiments on the 

 capacity of electrolytic condensers {Physical 

 Review, II., p. 401). Attempts to find con- 

 densers of this type which should be eflBcient 

 and free from ' hysteresis' led to the trial of 

 lead electrodes in sulphuric acid. As a con- 

 denser this form of cell was ho improvement 

 over those first used. But when placed in an 

 alternating current circuit a curious instance of 



alternating current electrolysis was observed, 

 namely, the development of insoluble lead sul- 

 phate at both electrodes. Experiments were 

 then made to determine the dependence of the 

 amount of electrolytic action upon current 

 density, frequency of alternation, temperature, 

 etc. The results, both in tabular and graphic 

 form, are contained in the present article. 



Polarization and Internal Resistance of a Gal- 

 vanic Cell: By B. E. Moobe and H. V. Car- 

 PBNTER. This article is devoted to an experi- 

 mental study of the ' diamond ' carbon cell, the 

 object of the authors being to localize the 

 changes in polarization and resistance which 

 occur on opening and closing the circuit. 

 Their chief conclusions are: (1) that polarization 

 occurs at both electrodes, but is more marked 

 at the carbon electrode ; (2) on closing the cir- 

 cuit the rapid fall of E. M. F. is due prin- 

 cipally to the polarization at the carbon elec- 

 trode ; (3) the rapid rise in E. M. F. , when a 

 cell is first thrown upon open circuit, is largely 

 due to recovery from polarization at the zinc 

 electrode. 



The Trace of the Gyroscopic Pendulum : By 

 Ernest Mebritt. In this article the motion of 

 the gyroscopic pendulum is first briefly discussed 

 from a theoretical standpoint. A number of 

 photographic traces are then shown, which 

 were made by reflecting a beam of light from 

 a mirror attached to the lower end of the 

 pendulum. Several different types of curves 

 are represented corresponding to different start- 

 ing conditions and to different lengths of pen- 

 dulum. These curves are of interest in afford- 

 ing a concrete illustration and confirmation of 

 the theory of gyroscopic motion. They also 

 bring out a curious effect due to friction, which 

 is exactly opposite in its result to what would 

 be at first expected. 



Note on Different Forms of the Entropy 

 Function: By W. F. Durand. Professor 

 Durand discusses, in this article, the general 

 form of the integrating factor which must 

 be used in order that the integral of dQ 

 shall vanish for any reversible cycle. It 

 has generally been recognized for some time 

 that the absolute temperature represents only 

 one of the infinite number of possible integra- 

 ting factors. If some other . of these factors 



