METEOROLOGY. 511 



We must abaudoii tbe couception that the summation of heat, which 

 has been ascertained for a certain vegetal phase at any one locality, 

 is a measure of the amount of lieat which that phase requires; but it 

 must be considered as a measure of the amount of heat which that 

 locality affords to the phase and to which the latter has accommodated 

 itself. Jt is, therefore, not a relation of cause and effect, but one of 

 accommodation that exists between sums total of heat and vegetal 

 l)liases; and it remains now to determine whether of our thernionietric 

 measurements these sums furnish the suitable measure in which this 

 accommodation is reflected. 



In the further prosecutions of these investigations the following 

 points should be kept in view: 



An instrument as nearly perfect as possible should be contrived for 

 the simultaneous measurement of light and heat, and the same style 

 of instrument should be used at all stations of observations. 



The starting point of the reckoning must be the same at all stations. 



As a fundamental condition the values obtained at any one station 

 must be constant from year to year for the vegetal stages in question, 

 which should always be observed on the same specimens. When this 

 has been demonstrated for sev^eral localities the values obtained at the 

 different stations for the same species can be compared one with another. 

 It will most certainly be found that these values are not equal one to 

 another; and it is probable that legitimate relations will be obtained 

 concerning the capacity of different plants to accommodate themselves 

 to the same climate, and the capacity of the same plant to accommodate 

 itself to different climates, i. e., the same relations which Linsser, as 

 early as 18G7, made a subject of investigations. 



Annual phenologic observations are now made in all European coun- 

 tries, excepting oidy the Balkan Peninsula, southern Italy, and Spain. 

 The reports are usually published once a year. The time of the first 

 blossoming of the most widely distributed woody plants is noted with 

 particular frequency; next in consideration comes the beginning of 

 foliation, the ripening of fruits, and the time when leaves change color 

 everywhere. The beginning of the blossoming time (first blossoms) is 

 the most readily observed phase. 



In order to obtain uniformly comparable results it is necessary that 

 the observations be made under normal conditions, i. e., on average 

 standard specimens, under normal (not extreme) exposure, otherwise 

 there is danger of noting an exceptionally early or exceptionally late 

 specimen. It lies in the nature of the matter that in noting the phases 

 it is not absolutely necessary to observe the same specimens in each 

 year. — o. l. fassig. 



Bibliography of the meteorology of the fifteenth, sixteenth, 

 and seventeenth centuries, (1. IIellmann ( U. 8. Dept. A(fr., Weather 

 Bureau Bui. 11, pt. ;2, h'pt. Tnteruat. MeteorouKj. Cniujress, isDS^pi. 2, pp. 

 352-3!H). — A list of about 250 books relating to meteorology and ter- 



