■REVIEWS. 
77 
of the science — have never been put clearly before the general reading public. 
We are glad, however, that an effort has now been made to place the history of 
aerial science before the reader of popular works. And we may sav at the 
outset that we consider that in discharging his task Dr. Hartwig has infi- 
nitely surpassed his former efforts in similar directions. Of the many 
popular works which this gentleman has given us we know of none that 
will compare, either for clearness of style or excellence of matter, with the 
present volume. 
He tells us in his preface that he has avoided giving such a character to 
the book as “would be required in a handbook of meteorology.” We think 
that in doing so he was actuated by most discreet motives ; for assuredly a 
book which would have been simply a meteorological text-book would have 
been excessively dry in reading, while such a subject as that he has chosen 
forni 3 , when properly discussed, a work which, once taken up, is very diffi- 
cult to lay down. Indeed, we should like to give a full notice of this 
highly interesting work, for throughout its pages we find that facts are most 
carefully stated, and are invariably surrounded with a valuable discussion, 
which takes away the dryness which would otherwise have surrounded 
them. However, as we cannot do this, we may at least give the headings 
of the several chapters, as that will help the reader to form a somewhat 
independent judgment. First, then, is a chapter on the magnitude and 
pressure of the atmosphere, and then follow others, for nearly 550 pages, on 
the ingredients of the atmosphere ; the propagation of sound through the 
air; echo; the colours of the sky; dawn and twilight; the temperature of 
the atmosphere; the winds; waterspouts, landspouts, tornadoes; fogs ; dew; 
clouds; rain; the rainbow; the mirage, spectre of the Brocken, halos, 
mock suns and moons ; snow ; the thunderstorm ; the means of preventing 
accidents by lightning ; the cyclone; St. Elmo’s fire; the ignis fatuus ; 
hail ; aerolites and shooting stars ; the aurora borealis and australis ; the 
primeval atmosphere; weather prognostics; the atmosphere and solid 
earth-rind ; the atmosphere and ocean ; the atmosphere and vegetable 
world; the aerial life of insects, birds, bats, and flying-fishes; influence of 
climate on man; flying machines; the balloon; the pleasures and perils of 
aerial navigation ; the great Nassau balloon ; scientific aerial voyages ; 
and lastly, the balloon in war. Out of this vast selection of interest- 
ing chapters there is but one passage which we will quote. And this 
refers to those comparatively recent researches in geology that prove 
beyond the possibility of doubt that the temperature of Greenland must 
have been once even warmer than our own. Dr. Hartwig says, page 365 : 
“At Anakerdluk, in North Greenland, in 70° N. lat., a large forest lies 
buried on a mountain, surrounded by glaciers 1,080 feet above the level of 
the sea. Not only the trunks and branches but even the leaves, fruit, 
cones, and seeds have been preserved in the soil, and enable the botanist to 
determine the species of the plant to which they belong. They show that, 
besides firs and sequoias, oaks and plantains, magnolias, elms, and even 
laurels, indicating a climate such as that of Lausanne or Geneva, flourished 
during the miocene period, in a country where now an almost perpetual 
winter compels even the hardy willow to'creep along the ground. During 
the same epoch of the earth’s history Spitzbergen was likewise covered with 
