374 Мовтем Р. Ровзио. Actinometrical observations from Greenland. 
once or twice a year. Moreover, it is of course equally necessary 
to have an exact understanding of the arrangement of the apparatus. 
If the results are to be of value for comparison the same glass- 
tubes and rulers, the same tracing- paper, etc. should be used, and 
the same method of work must be followed. All the apparatus 
which is employed should, at some time, be compared with a 
standard apparatus. 
The photometrical investigations of WIESNER and his school 
have already obtained important results in plant-physiology. Although 
these investigations have been carried out in almost all climates 
they are yet new and in an embryonic condition; probably in the 
future they will be introduced everywhere in the service of climat- 
ological investigations. The chief advantage of the STEENSTRUP- 
method lies in the fact of its being extremely convenient to mani- 
pulate, an advantage which should not be underrated in cases where 
daily investigations are wanted year by year. Therefore it appears 
to me very desirable that this method should be thoroughly com- 
pared with that of WIESNER so that the measurements obtained 
by the one method may be readily converted into the units of the 
other. Both methods will probably supplement each other very 
successfully, according as to whether it is deSired. to register the 
chemical light-intensity at any one particular minute, or the intensity 
for the whole day. 
Literature. 
Dr. К. J. V. STEEnSTRuP’s apparatus was described by the inventor in 1901, in 
Danish and in French, in “Meddelelser om Grønland”, XXV; the description was 
repeated in 1902, in "Fysisk Tidsskrift”, No. 2. In the succeeding numbers of the 
latter journal K. Pryrz published a physical investigation of the apparatus; further, 
a discussion was there carried on between the latter investigator and A. PAULSEN. 
Also, in “Ugeskrift for Leger”, 1903, there is published a debate between A. PAULSEN 
and J. MyGGE. Lastly, STEENSTRUP published in "Fysisk Tidsskrift” (III, 2) a paper 
on “De daglige Lysmængder 1 et Aar, etc.” 
J. WIESNER: “Der Lichtgenuss der Pflanzen,’ Leipzig, 1907, contains the prin- 
cipal results arrived at by that investigator, and the numerous investigations initi- 
ated by him; also an exhaustive list of literature. The results obtained from 
experiments made under Arctic conditions are found in: — 
J. WIESNER: Beitr. z. Kenntn. des photochem. Klimas im arktischen Gebiet 
(Denksch. math. nat. Cl. Kaiserl. Ak. Wien, LXVII.), Wien, 1908. 
J. WIESNER: “Beitr. 2. Kenntniss des Lichtklimas von Troms6,” etc. Tromsö 
Museums Aarshefter, 24, Tromso, 1901. 
29.—3.—1911. 
