xxxviii GENERAL SUMMARY OF SCIENTIFIC AND 



certain fine telluric lines in the solar spectrum "become dark 

 smoky bands when the quantity of moisture is abnormally 

 great. 



Scheme has given some careful measurements showing the 

 presence in minute quantities of the hyperoxide of hydrogen 

 in the atmosphere ; and Dr. Ecke has published an extensive 

 investigation into the relative quantities of oxygen in the air, 

 and in the different climates and at different seasons. His 

 studies have special reference to the sanitary advantages of 

 certain localities. 



Temperature of the Air. Dove contributes to the Berlin 

 Academy a valuable paper on the climatology of Germany, 

 based on observations of temperature made during twenty- 

 five years, from 1848 to 1872, at two hundred and six stations. 



Celoria elucidates the general laws of variations of temper- 

 ature, both annually and daily, by one hundred and ten years 

 of observations at Milan. 



From the examination of forty years of observations of the 

 temperature at Brussels, Quetelet finds that the so-called 

 cold days of May actually exist for that place, giving rise 

 to a well-marked depression, amounting on the average of 

 the whole period to three degrees of temperature. 



Silbermann has observed the temperature of a small mass 

 of black powder exposed to the sun's rays, and has applied 

 his results to explain the cases in which the northern sides 

 of mountain chains are more fertile than the eastern sides. 



In reference to the production of frost, Ley states that a 

 study of the upper currents of the clouds has shown him that, 

 at least in England, frosts are preceded by a slight backing 

 of the upper southwest and northwest currents. 



Barometric Pressure. The relations between the baromet- 

 ric pressure and the velocity of the wind have formed the 

 subject of valuable contributions to the Journal of the Aus- 

 trian Meteorological Association, where Hann has developed 

 the mechanical formula of Ferrel, and given a translation of 

 the work of Colding, of Copenhagen ; the latter shows the 

 perfect agreement of his formula with observations made 

 during certain hurricanes in 1837 and 1871. Mr. Fen-el's 

 formula) are, however, preferable to Colding's. 



A very complete review of the state of our knowledge with 

 respect to the connection between barometric pressure and 



