44. ©. Barrois— Review of Professor Halls recent volume 
This interpretation is perhaps most readily imparted by a 
comparison of the hot convection currents in the two cases. 
When the convection current is rising vertically, the medium 
is cooled by expansion until the precipitation temperature is 
reached, when all the condensible material appears suddenly, 
save as it is somewhat retarded by the heat liberated in the 
act. Immediately afterward the particles become relatively 
dark by radiation. In the horizontal current a very different 
condition of things obtains. Here the medium does not cool 
dynamically by expansion, but only by radiation ; hence, since 
the radiation of the solid particles i is enormously greater than 
that of bie supporting gas, pane by that of = particles 
f b 
themselve us after the first particle appears, it must 
remain at its brightest incandescence until all ihe: Ree of 
which it is composed is precipitated. From this we see that 
such a horizontal current must increase gradually in Dabinse 
to its maximum, and then suddenly diminish, an exact accor 
ance with the facts as observe 
Johns Hopkins Univ., Baltimore, Sopitnbin. 1880. 
Art. IV.— Review of Professor aed recently published volume 
on, the Devonian fossils of New York (constituting Part Pie 
vol. v, of his hoes series on the Palesotalosy of the State) ; 
by Dr. Cu. BARROI 
TuE State of New York has recently published the second 
part of vol. v, of the elie 2) of New York, by Professor 
Before presenting to the readers of the Revue the scientific 
results acquired in this important work, it is proper to refer to 
the volumes which preceded it, and to speak of the immense 
charge which the State has confided to Professor Hall, a charge 
which has given to science the geology, and then the Paleon- 
tology, of New 
The first eacarelies of Professor Hall were made in the 
State of New York in 1837. He was appointed by the Gov- 
ernment, with Mather, Vanuxem and Emmons, to collect - 
materials for a geological desaviption of that region. Durin, 
tie ged which followed, the annual reports of these cei 
* This w appeared in the number of the Revue piego rms (Paris) for 
September, 1880. and has been translated from the French for this Journal. € 
ars the date December 15, 1879, Albany, New York. 
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