234 Scientific Intelligence. 



ular formulas and structure are explained and illustrated by 

 a careful study of derivatives of methyl and ethyl alcohols. In 

 the second part the aliphatic compounds are described more 

 systematically, while the third part is devoted to a brief treat- 

 ment of the more important members of the aromatic series. 



The book appears to be an excellent one for the purpose in 

 view. The explanations are clear, the laboratory experiments 

 are well selected, and each chapter, of which there are twenty-six, 

 is supplied with a list of questions, while there are, at the end 

 of the book, some general questions, as well as some very instruc- 

 tive problems upon the calculation of formulas from such data as 

 are usually obtained in practical research. h. l. w. 



6. Electric Discharge in Gases and Vapors. — The facts 

 recorded below are derived from a recent paper by R. J. Strutt. 

 The first part of the investigation relates to the phenomena pre- 

 sented by luminous jets at low pressures in a transverse electric 

 field. The gas was excited to luminosity during its passage 

 through a glass bulb of about 16 cm. diameter. The anode con- 

 sisted of an iron disc which was soldered into the end of a brass 

 tube. The disc was perforated at the center by a hole 1 mm. in 

 diameter. The brass tube formed the prolongation of a small 

 lateral glass tube which was blown on the wall of the spherical 

 bulb. This outlet tube was diametrically opposite to, and 

 coaxial with, the inlet tube. The cathode was fixed close to the 

 inner wall of the bulb at 90° from the openings of the coaxial 

 glass tubes. The current was produced by three high-tension 

 magneto generators arranged in series and direct driven by a 

 motor. The maximum output of this system was 10 milliam- 

 peres at 5000 volts. The variation of the current from a con- 

 stant value did not exceed ±0-22 per cent. After passing 

 through the hole in the anode the gas escaped as a jet into a 

 large cylindrical glass tube the axis of which was perpendicular 

 to the common axis of the brass and glass tubes mentioned above. 

 The transverse glass tube contained two condenser plates the 

 planes of which were parallel to the axis of the jet. This tube 

 was closed at one end by a plate glass window through which 

 the light from the jet passed to the camera lens. The gas 

 finally escaped through a lateral tube to a molecular pump. 

 The condenser plates were 13 mm. apart and they usually had 

 a difference of potential of 160 volts. The luminosity of the 

 jets was too low for visual observation so that the photographic 

 method could not be avoided. The pressures were not measured 

 directly but were controlled by the length of the negative 

 dark space. 



The gases investigated with this apparatus were hydrogen, 

 oxygen, nitrogen, carbon dioxide, and mercury vapor. With 

 hydrogen at a pressure corresponding to a dark space of 6 mm. 

 the bulk of the luminous particles were attracted to the positive 



