102 
one may multiply the duration of sunshine by the percentage of 
observed clearness and obtain the duration of sunshine for a special 
station. But this will give us a value that is greater or less than the 
value of the true intensity of sunshine according as the cloudiness 
occurs mostly in the morning and evening or in the midday hours. 
The only method for obtaining a satisfactory value of the intensity 
of radiation as coming direct from the sun or as reflected from the 
sky, the clouds, and the earth, is to maintain a self-registering acti- 
nometer or, in place of that, frequent daily observations. 
Tn these tables I have adopted the division of each month into three 
parts, as done by Libbey and occasionally used by meteorologists, but 
the system of pentades, used by Dove, is often preferable; however, 
this present system is convenient for monthly summations, and is also 
used in the climatic table of Section IT." 
Sums total of possible duration of sunshine, in hours, from January 1 up to any 
day of the year. 
Num- | Latitude. 
Interval. ber of | 
days. | 24°. 26°. 28°. 30°. 82°. 34°. 4) 36°. 
| Hours. | Hours. | Hours. | Hours. | Hours. | Hours. | Hours. 
Tanuary 110.000 10} 106.7] 105.4] 104.0} 1025] 101.0) 99.4] 97.7 
Senusyall =A) eee eee 10 | 214.5 212.0 | 209.3 206. 4 203.5 200. 4 197.2 
Januaryeol_3 lees =a 11 | 334.7 331.0 327.1 322.9 318.7 314.2) 309.5 
February 1-10.....-..-------- | 10) 446.0] 441.4) 486.6] 431.4] 426.2] 4206) 414.9 
RMehnruaiysll 20s 2. -e = aces | 10 | 559. 4 54. 1 548. 6 542.6 536. 7 530. % | 523.7 
Mebmuanry, 21-282... ee | 8 | 649.9 645.2 640.3 633.9 627.6 €20.6 | 613.6 
Marche! =| pee See | 10| 767.4 762.4 | 57.2 750.5 743.8 736.4 729.0 
Marchild =) ae nem eae nee 10 | ~- 887.2 882.1 876.8 870.0 863. 2 855.7 848.2 
Manehizia sist. sess sees ee 11 | 1,021.7 | 1,016.8 | 1,011.7 | 1,005.0 998. 4 991.1 983.7 
eA Orsi G1=i (ue eee ee oot ee | 10 | 1,146.4 | 1,141.9,| 1,187.2 | 1,180:9 | 1,124.7 | 1,117.9 | 1,110.9 
PA nil Gil 0 Reese one cone ke ee 10 | 1,273.8 | 1,269.4 | 1,265.3 | 1,259.7 | 1,254.2 | 1,248.1 | 1,241.8 
IS WeAS eae 10 | 1,402.3 | 1,399.2 | 1,396.0 | 1,391.3 | 1,386.7 | 1,381.5 | 1,376.2 
Mayal=1 0 eses- 2 een. See opeees 10 | 1,583.3 | 1,581.2 | 1,529.0 | 1,525.4 | 1,521.9 | 1,517.9 | 1,518.8 
Ma yell 20 tae a ea ee 10 | 1,666.0 | 1,665.1 | 1,664.1 | 1,661.8 | 1,659.6 | 1,657.0 | 1,654.3 
Maye 21 3)e a2 aaa os oe 5 Sats 11 | 1,813.6 | 1,814.1 | 1,814.6 | 1,818.8 | 1,813.2 | 1,812.4 | 1,811.4 
SIUM =) One ween eee 10 | 1,948.8 | 1,950.7 | 1,952.7 | 1,958.4 | 1,954.4 | 1,955.3 | 1,956.0 
JUNE w= COP ese eee 10 | 2,084.5 | 2,087.9 | 2,091.4 | 2,093.7 | 2,096.3 | 2,099.0 | 2,101.5 
UNC 21 OO ee eae eee ee | 10 | 2,220.2 | 2,225.1 | 2,230.1 | 2,234.0 | 2,288.2 | 2,242.7 | 2,247.0 
spitiliyilh 10 ee ees So ten 10 | 2,355.4 | 2,361.7 | 2,368.2 | 2,373.6 | 2,379.4 | 2,385.6 | 2,391.6 
Anebh: UO) ak Re ee eee 10 | 2,489.7 | 2,497.3 | 2,505.2 | 2,512.0 | 2,519.3 | 2,527.1 | 2,534.7 
SLyAeasl ess es ee eee 1] | 2,636.0 | 2,644.9 | 2,654.1 | 2,662.3 | 2,671.0 | 2,680.4 | 2,689.6 
JNU WEN) 2s oe eee 10 | 2,767.1 | 2,777.1 | 2,787.3 | 2,796.6 | 2,806.4 | 2,817.0 | 2,827.5 
PANTS TIS tll 20 eens ee ee 10 | 2,896.3 | 2,907.1 | 2,918.1 | 2,928.3 | 2,939.0 | 2,950.6 | 2,962.1 
PRU AVAL BIL Se os ae so 11 | 3,036.1 | 3,047.5 | 3,059.2 | 3,070.2 | 3,081.7 | 3,094.1 | 3,106.4 
September 1-10 -_____-_------ 10 | 3,160.8 | 3,172.6 | 3,184.7 | 3,196.1 | 3,208.0 | 3,220.9 | 3,233.6 
September 11-20 _._..__.__--. 10 | 3,283.2 | 3,295.2 | 3,307.4 | 3,319.0 | 3,331.1 | 3,344.2 | 3,357.1 
September 21-30 __.-._.___--- 10 | 8,403.3 | 3,415.2 | 3,427.4 | 3,489.0 | 3,451.0 | 3,464.0 | 3,476.9 
Octoberpl=l02 essa ea a eee 10 | 3,521.1 | 3,582.7 | 3,544.6 | 3,555.9 | 3,567.6 | 3,580.2 | 3,592.8 
Octobersili20 yeas ae eee 10 | 3,636.6 | 3,647.7 | 8,659.1 | 3,669.9 | 3,681.0 | 3,693.0 | 3,705.0 
Octopers2i—o Meas eae eee 11 | 3,761.2 | 3,771.5 | 3,782.1 | 3,792.1 | 3,802.3 | 3,813.4 | 3,824.5 
November 1-10. -.-.-.-.------ 10 | 3,872.3 | 8,881.7 | 8,891.3 | 3,900.3 | 3,909.4 | 3,919.4 | 3,929.4 
@ Omitted. 
