B. TERRESTRIAL PHYSICS AND METEOROLOGY. 113 



ATMOSPHERIC ELECTRICITY. 



The last number of the Transactions of the Academy of Sci- 

 ences of St. Louis contain the result of the observations on 

 atmospheric electricity made by Dr. Wislizenus during the 

 twelve years from 1861 to 1872. Throughout this series of 

 observations the same apparatus has been used, being con- 

 structed on a method adopted by Dellmann; the observations 

 are therefore strictly comparable among themselves, and 

 seem to Dr. Wislizenus to justify certain conclusions, which 

 he announces as follows : 



"As an important addition to our knowledge of atmos- 

 pheric electricity, I consider the discovery of its threefold 

 periodicity the daily, annual, and secular periods ; the daily 

 periods are not so constant that they show themselves every 

 day, but are distinctly perceived when we take the average 

 of a week, a month, or a year. The annual period exhibits 

 itself in a regular increase in the quantity or intensity of elec- 

 tricity during the six colder months of the year, and of a de- 

 crease during the warmer months, the extremes being in 

 January and July. The yearly means for the twelve years 

 show that tliere was a gradual increase from 1861 to 1863; 

 then a decrease for five years, and again an increase for four 

 years up to 1872, seeming thus to establish a cycle of about 

 ten years, similar to that of the magnetic phenomena of the 

 sun's spots." Wislizenus believes in the practical usefulness 

 of electric observations for meteorological predictions, and 

 suggests that the Army Signal Bureau, by means of a dozen 

 stations well selected throughout the United States, might 

 materially improve the accuracy of its storm predictions. 

 Trans. St. Louis Acad., 172. 



ox THE CAUSES WHICH PROVOKE STROKES OF LIGHTNING. 



De Fonvielle has presented to the Paris Academy of Sci- 

 ences a short study on the subject of lightning strokes, in 

 Avhich he maintains that two neici-hborino: conducting^ bodies 

 react forcibly upon each other Avhen they are found under 

 the influence of a thunder-cloud, and that this reciprocal in- 

 fl.uence is not the same when the conductors are isolated as 

 it is when they are placed in communication with a common 

 reservoir such as the earth. The author endeavors to ex- 



