METEOROLOGY AND ALLIED SUBJECTS. 



331 



the occurrence of the respective botanical phases. He finds the obser- 

 vations of plants that blossom in early sprinjjf very irregularly affected 

 by early frosts, but gives the following table for plants that flourish in 

 summer and autumn. Three thermometers have been used exposed 

 under very similar circumstances — Kos. I and II, during 1880, No. Ill, 

 during the earlier period, 186G to 18G9. 

 The results seem very closely comparable among themselves. 



PlaDt. 



Date of first 

 blossom, 

 1880. 



Thermal constant for the years. 



I.— 1880. II.— 1880. m.— 1866-'69 



Acaculas raacrostachya. . . 



Catalpa syiinj^aifolia 



Linosyris^ vulgaris 



Mirabilis Jalapa 



Plnmbafro ouiopaia 



Pulicaria dyseuterica 



Valoradia plurabaginoidea 



Vites vinifera 



Lilium candidum 



Aster AmeUus 



vn,2i 



VII, 23 



VIII, 14 



VII, 31 



X,5 



VII, 25 



IX, 2 



VI, 22 



VI, 29 



VIII. 14 



3,504 

 3,557 

 4,091 

 3,776 

 5,495 

 3,618 

 4,767 

 2,697 

 2, 872 

 4,091 



3,191 

 3,229 

 3,753 

 3,441 

 5,954 

 3,292 

 4,352 

 2,603 

 2,603 

 3.753 



3,353 

 3,318 

 4,033 

 3, t43 

 5,318 

 5,381 

 .5, 177 

 2,606 

 2,710 

 3,930 



Hoffman finds evidence that this law also holds good for plants pro- 

 tected in greenhouses, and further, that the mean temperatures in the 

 shade cannot have such a connection with the development of the plant 

 as have those shown by the insolation thermometer. {Z. 0. G. j\L, XVI, 

 1881, pp. 331-334.) 



{(1) Meteors. — Br. J. H. L. Flogel communicates observations by him- 

 self on particles of iron dust found in snow, and gives a summary ot 

 previous researches on this subject, beginning with Ehrenberg in 1849. 



The first snowfall examined by Flogel gave in the purest melted snow 

 water nine forms of diatoms, confervas, spores, alive or apparently alive; 

 fourteen forms of pollen or other parts of animals and plants ; and five 

 forms of mineral substances. The subsequent snowfall, however, be- 

 side these forms of dust, invariably gave iron, and the total amount of 

 the latter was in one case about ? 3ooooooo of the volume of fresh- 

 fallen snow. 



Flogel admits that- the cosmic origin of this iron dust (and Grone- 

 man's theory of the dependence of auroras upon its presence) is very 

 plausible, but that it still needs to be proven to be of local terrestrial 

 origin, and be specially confined to certain regions of the globe. The 

 question will probably be best settled by investigating the presence of 

 nickel, as, if present, it would argue irresistibly for the cosmic origin of 

 this iron dust. {Z. 0. G. ilL, XVI, 1881, p. 321.) 



