ae ea 
~ since May, 1844, and notices of some of his results have appear- 
ed in this Journal. A recent publication, whose title is given be- 
served in each case, but a sketch of a portion of the dust as it 
vom 23. Mai 1844 bis 1849. Abhandlungen der Akad., 1847. 192 pp. 4to' 7 
372 On Infusoria in Dust-showers and Blood-rain. 
These calculations, however, are liable to error from many 
sources. Very different results might generally be obtained from 
different sides of the sgme island; and the same group often con- 
tains islands without reefs, and others with reefs one or even sev- 
eral miles from the shores. But since we may show that the 
absence of a reef or its limited extent may be traced to some 
causes restricting or modifying its formation, it is obvious that 
the error would probably be on the side of too low an estimate. 
Adjacent to the larger islands, such as those of Vanua Levu an 
ew Holland, the error might be of the opposite kind; for the 
slopes of the land are of a more complex or irregular character 
than on the smaller islands. In the latter, they may be shown to 
belong generally to a single elevation of igneous origin, or at.the 
most to two or three combined; while in the former, they may 
pertain to different ranges of hills or mountains. For correct re- 
sults in any instance, the land and its declivities should be care- 
fully studied beforehand, and the system in its inclinations deter- 
mined by observation. With regard to Tahiti and Upolu, in- 
formation bearing upon this point was obtained, and the above 
conclusions may be received with much confidence. Many of 
the Feejee reefs, on the same principle, cannot be less than 2000 
feet in thickness. 
Arr. XLIT.—On the Infusoria and other Microscopie forms 
in Dust-showers and Blood-rain ; by Dr. C. G. Eurensere.* 
Tue infusorial character of the dust occasionally transported 
by winds, is one of the most wonderful of Ehrenberg’s discove- 
ries. His investigations have been reported from time to time, 
low, contains the details of his various researches, with full illus- 
trations. ‘The plates contain not only figures of all the forms ob- 
® Passat-Staub und Blut-Regen, ein grosses organisches 
und Leben in der Atmosphiire ; Mehrere Vortrii 
outs i J } i ey r 
Wiss. zu Berlin, &c. Vorgetragen in der Kénigl. Preuss. Akad. der Wiss. zu 
