Actinometrical observations from Greenland. 367 
are considered here I have compared them in Table II, where 
consequently every difference lying between 1 and 79 of the rela- 
tive intensity-value belonging to the numbers may be obtained 
directly. 
For instance if the number 40 has been read one day and 50 
the following day, the intensities in question are not as 4 to 5, but, 
as shown in the table, as 1 to 3'8: it may perhaps be noted as ап 
example that with regard to the differences of the actinometer 
numbers, a difference of 5 or 12 or 17 means an intensity relatively 
larger or smaller by 2, 5, or 10 times. 
A glance at Table II will show that the relative values increase 
logarithmically; also that in cases where high differences occur, the 
comparison of the intensities becomes very inaccurate, as an егго- 
neous reading of a single degree will occasion a very considerable 
error, while in case of low differences a similar error is insignificant 
or of no importance at all. 
Total light from day to day. 
On considering more closely the numbers in Table I we observe 
that the difference of light from day to day amounts to a maximum 
of as much аз 12—14 degrees, i. e., at almost the same altitude 
of sun and length of day, cloudy weather can reduce 
the intensity of the chemical light to about "7. But usu- 
ally the differences are far slighter, only one or two degrees as a 
rule, i. e. they do not exceed the accuracy of the reading. Similar 
numbers are to be found in the two Danish series published by 
STEENSTRUP. Moreover it will be seen that it is especially in the 
Arctic regions that the differences are greatest during sum- 
mer, while they sink toa minimum during winter. We 
will return later on to this subject. 
The Influence of the Altitude of the Sun. The regular changes 
during the year in the Light-totals. 
Table III., Monthly and yearly Mean of the Actinometer Numbers. 
Jan. | Feb. March April May June | July| Aug.| Sept. | Oct. | Nov.| Dec.| Year 
Disco 1907 ...... | AR TN | Gob os SN A NE RE RS CA Цао 
War... 21 136) 02 | 67 70 Ka 16 p47 4 | 98 | 13 
= 17 | 39°| oa eee Ml 
Anholt \ Bere | = | 4 | er 
1903. VIL_1904.VI. F- 42 | 51 | 56 | 63 | 69 | 69 | 65 | 63 | 60 | 49 | 44 40 | 56 
Copenhagen 5 | 42 5 | | 33 |5 
qe Ат 35 в. 50 | 54 | 59 | 62 | 61 | 59 | 54 | 48 | 43 | 33 | 50 
