CG ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



etc., show that there is a considerable independent activity 

 in weather observation. 



INSTRUMENTS AND METHODS. 



The application of the thermo-electric pile to the study of 

 terrestrial radiation has been treated of by Frolich in Wild's 

 Hepertorium. He employed a blackened surface as his nor- 

 mal standard ; this was heated to known temperatures, and 

 its effect upon the pile observed. An empirical formula was 

 thus obtained, which gave the temperature of the surface as 

 a function of the movements of the galvanometer needle. 

 The instrumental constants being thus known, the face of the 

 pile is to be turned towards the sky, and the temperature 

 then observed becomes the basis of further computations, 

 whence the mean temperature of the atmosphere and eventu- 

 ally the mean temperature of exterior space may be deduced. 

 As illustrating his results, Frolich deduces for the mean 

 temperature of the atmosphere 17 C. on August 17 and 

 36 C. on October 23, 1876. 



Dr. Buff, of Giessen, describes a method by which he at- 

 tempts to make the thermo-electric pile an important mete- 

 orological instrument. He claims that it enables us to meas- 

 ure the greater part of that portion of the sun's rays which 

 lias not yet been converted into sensible heat. Dr. Buff's 

 method of operating consists in exposing both ends of the 

 pile to the temperature of the air when the needle assumes 

 its zero position. The upper end is then exposed to any por- 

 tion of the sky, when, of course, the needle indicates heat or 

 cold, according to the position of the sun and condition of 

 the sky. If, now, a plate of glass is held as a screen to this 

 exposed end, it cuts off all rays of low refrangibility, and the 

 needle returns partially, but never during the daytime en- 

 tirely, to its zero. With a perfectly clear sky, and without 

 the glass screen, the radiation of the exposed end caused, for 

 instance, an indication of 50, but protected by the glass 

 screen an indication of +10. On another day the blue 

 heavens gave 30, the glass screen +20, and the clouds 

 + 50. The ends of the pile are covered with lamp-black, 

 whose radiation is nearly the same as that of the green 

 haves, and the instrument, therefore, gives a just idea of the 

 range of temperatures to which leaves arc subject. It is a 



