New York Weather Bureau. 



453 



The effect of the elevated position and open exposure of the 

 hill tops in decreasing the daily range is here apparent. 



For comparison with the above the following mean daily ranges 

 at stations of the National Service are given, the means embrac- 

 ing the five-year period, 1881-1885. 



It will be seen that at Block Island the mean daily range 

 owes its principal component to the irregular temperature 

 changes which takes place from day to day, since the range is 

 at its maximum during the months of greatest temperature vari- 

 ability, when, ooa the other hand, the small amplitude proper is 

 at its minimum. 



The fact that the instrument shelters at National Weather 

 Bureau stations are loeated at a considerable distance from the 

 gpoiund (the average height in this State being over 100 feet) may 

 in part explain the lesser range at these stations as compared 

 with some of the values obtained by the State Bureau. 



Valley Winds and Inversions of Temperature. 



During clear nights, both in winter and summer, the ground 

 loses heat rapidly by radiation, and the air, in contact with it, 

 becoming cool and dense, flows down the slopes towards the 

 lower levels of the valleys. In central Europe this phenomenon 

 appears to be most noticeable in winter, being greatly strength- 

 ened by the intense anticyclonic conditions which often occur 

 during that season; while in New York the rapid radiation which 

 is necessary to the process is usually checked by clouded skies 

 during the colder part of the year. 



