chap. in. TABLES OF TEMPERATURE. — HEBERDEN. 



39 



Dr. Heberden's account of monthly maxima and minima 

 of temperature in Madeira, as observed a century ago, shows 

 an amount of variation similarly small. 



Dr. Heberden's Tables. Phil. Trans., x. abr., 1751, 232. 



" Dr. Heberden goes on to give the mean height of the 

 barometer and thermometer at Funchal for each month of 

 the years 1751, 1752, 1753, which have but very small 

 differences and changes. 



" By collecting the respective sums of the daily heights of 

 the instruments throughout the year, and extracting the mean 

 altitude, it is found that the mean altitude of the barometer 

 for each day is 29-915 inches, and of the thermometer 

 68°-918. The greatest thermometrical variation during the 

 said time has been 20°, viz., from 60° to 80°; but it may be 

 observed that it never rose so high but once, occasioned by a 

 very strong L'Este, or Levant wind, the extreme height, 

 without such an accident, being never more than 78°." 



