20 



INTENSITY OF SUN'S HEAT AND LIGHT. 



Let it also be observed, that the Menclon values are the monthly means, which do 



not always fall on the 15th day, but nearly at that time. 



Rate per Hour of the Sun's Intensity. — To glance at the subject from another 



point of view, let us consider the Rate, or the relative number of heating rays per 



hour. For any day, if we divide the computed Intensity by the length of the day, 



the quotient will express the average Hourly Intensity, denoted by R ; thus, 



n — tan H , , 



R = jg - i [5.94210] A 2 sin L sin D {—jf~ ± 1). (19.) 



In the accompanying table, the values of the rate R are exhibited at intervals of 

 fifteen days, and for every ten degrees of latitude. From this, Plate II is con- 

 structed ; and for comparison with the Daily Eate of Intensity, the Daily Kange of 

 the Thermometer is also delineated for Trinconomalee, on the coast of Ceylon (lat. 

 9° N.) — taking 5°. 72 Fahr. plus ith of the mean daily ranges, as ordinates; also 

 for Philadelphia (lat. 39° 57'), taking here 7° plus ird of the daily ranges; for 

 Gottingen (lat. 51° 32'), taking Jrd of the daily ranges; and for Boothia Felix (lat. 

 70° N.), taking f^ths of the daily ranges in degrees Fahrenheit as ordinates. These 

 changes are arbitrary, but are analogous to the conversion of thermometric scales, 

 and still preserve the original law of the curves. The peculiar inflexion at the 

 vertex of the curve of Hourly Intensity for latitude 70°, evidently arises from the 

 change to constant day. And apparently the hourly rates of Plate II, coincide 

 more nearly with the temperatures of Plate I, than do the Diurnal Intensities, or 

 absolute amounts. 



Average Rate of the Sun's Hourly Intensity, or Relative Number of Vertical Rays per Hour. 



(Plate II.) 



A. D. 1853. 



Lat. 0°. 



Lat. 10°. 



Lat. 20°. 



Lat. 30°. 



Lat. 40°. 



Lat. 50°. 



Lat. 60°. 



Lat. 70°. 



Lat. 80°. 



Lat. 90°. 



Jan. 1 . . . 



C.43 



5.89 



5.16 



4.24 



3.26 



2.08 



0.88 









" 16 







6.51 



5.99 



5.32 



4.44 



3.44 



2.32 



1.12 









" 31 







6.63 



6.20 



5.56 



4.66 



3.86 



2.75 



1.56 



0.34 







Feb. 15 







6.75 



6.38 



5.85 



5.05 



4.27 



3.22 



2.11 



0.92 







Mar. 2 







6.80 



6.59 



6.11 



5.50 



4.71 



3.78 



2.70 



1.56 



0.35 





" 17 







6.83 



6.70 



6.38 



5.85 



5.15 



4.25 



3.17 



2.21 



1.03 





April 1 







6.73 



6.71 



6.50 



6.09 



5.51 



4.73 



3.82 



2.76 



1.64 



<X86 



" 16 







6.58 



6.67 



6.56 



6.21 



5.70 



5.02 



4.24 



3.22 



L83 



1.86 



May 1 







6.40 



6.59 



6.57 



6.33 



5.86 



5.32 



4.50 



3.52 



2.68 



2.72 



" 16 







6.23 



6.48 



6.53 



6.40 



6.01 



5.46 



4.71 



3.55 



3.35 



3.40 



" 31 







6.08 



6.39 



6.49 



6.36 



6.07 



5.54 



4.78 



3J52 



3.79 



3.85 



June 15 







6.00 



6.33 



6.45 



6.34 



6.07 



5.57 



4.81 



3.82 



4.00 



4.07 



July 1 







6.01 



6.32 



6.44 



6.36 



6.12 



5.58 



4.83 



3.78 



3.96 



4.03 



" 16 







6.08 



6.38 



6.46 



6.37 



6.01 



5.51 



4.75 



3.51 



3.68 



3.74 



" 31 







6.22 



6.46 



6.50 



6.32 



5.98 



5.42 



4.65 



3^55 



3.18 



3.22 



Aug. 15 







6.39 



6.56 



6.50 



6.30 



5.S7 



5.23 



4.3S 



3.43 



2.47 



2.50 



" 30 







6.54 



6.60 



6.48 



6.12 



5.53 



4.87 



4.05 



3.10 



L90 



1.62 



Sept. 14 







6.64 



6.60 



6.37 



5.92 



5.45 



4.70 



3.08 



2.61 



1.50 



0.61 



" 29 







6.70 



6.57 



6.21 



5.68 



4-93 



4.05 



3.16 



2.04 



0.89 





Oct. 14 







6.73 



6.47 



6.01 



5.36 



4.53 



3.58 



2.56 



1.42 



0.22 





" 29 







6.66 



6.29 



5.74 



5.00 



4.08 



3.09 



2.00 



0.80 





'. '.'. 



Nov. 13 







6.56 



6.12 



5.48 



4.72 



3.75 



2.66 



1.48 



0.25 







" 28 







6.46 



5.95 



5.26 



4.42 



3.36 



2.28 



1.08 









Dec. 13 







6.40 



5.86 



5.13 



4.25 



3.28 



2.06 



0.87 









