The sun. [volume] (New York [N.Y.]) 1833-1916, 1891-12-06


comparatively near The sun. Tho formstio
OF Zoe and snow during winter must have bee
carried on upon very restricted scale. II mo-
indeed wholly prevented. On the other hand
the summer in this delightful climate woul
contain a. great number OF days as IL 10 pos
| sible for that season to possess but the herc
heat Of the sun would be abated from It's aver
age amount because the sun during all tina
season would DO placed at the greatest dis
tance from the Garth which It is possible for I
to attain. 30 definite are tho Astronomical
| elements OF the problem. and 90 obvious ar,
| the climatic changes involved. that Sir Rober
Ball considers that we are justified In assert
ing that tho earth must have passed through
many repetition OF great eli mstio changes.
Evidently. however,. It would be mistake X
suppose that extreme cold is the sole reoui
| site for the formation OF an Ice age That Il
| certainly not tho case. for Q largo supply ol
| heat somewhere or other is also necessary
| element In the production Of an ice sheet Fol
| what is an Ice sheet but an accumulation oil
the snow which has fallen7 That snow has. oil
course. como from the clouds In which The
moisture which forms the snow was SUSPENDED
as vapor. This moisture had. OF course. to be
derived from the seas covering tho globe. Az
the sunbeams pour down on the wastes OF sea
they evaporate tho water which In the form Of
invisible vapor ascends Before . pound
weight Of ice can DO manufactured for .
fallen: to produce that pound weight OF snow
the sun must have raised . pound Of water in
the form OF vapor from the surface Of the
sea. Thus We see how important . factor
heat must have been even In the formation
OF tho Ice sheet Tho astronomical theory OF
tho ice age shows MS at once whore to look for
tho heat 80 indispensable TO the accomplish
mont OF glaclation. Even when the esrth's
orbit hos It's highest degree Of eocentricity.
and when the severity OF an ice age 10 at .
maximum. tho total quantity OF heat which
the earth receives during the year 10 not les
sened. H. therefore. the glaciated hemisphere
receives during its winter deficient supply OF
heat, to which deficiency the glaciation owes
its origin. the defect Of heat upon this hemi-
sphere 10 compensated BY q superabundance
elsewhere More favored regions Of the globe
enjoy Q more copious supply Of sunbeams.
and thus arc provided the volumes Of aqueous
vapor which. put In circulation BY the wind.
are deposited In the form Of snow where the
ice sheets are grown.
In word. the explanation here offered Of
the Zoe age depends upon tho consequences
Of an irregularity In the supply Of heat from
season to season. Notwithstanding that the
total amount received in q year remains un-
altered. Nor is It likely to be denied that such
great irregularities In the supply. as Sir Rob-
ert Ball has shown to be the outcome Of suit
able combination OF astronomical conditions.
must correspond to great climatic changes.
Nv.
Tho error IN the astronomical theory Of the
Ice age. which has been corrected By the au-
thor Of this treatise. first pointed out By him
In lectures delivered at tho Royal Institution
and before the Royal Dublin Society. Sir John
Herschel. and following him apparently. DR..
Croll and other expounders Of glacial phe-
nomena. asserted that under glacial conditions.
half the annual supply Of heat received by
given hemisphere was oonoen trated In q sum-
mer OF very short duratio n. while the other
half was spread over q long and dreary winter.
1t was reserved for Sir Robert Ball to discover
the law that under all circumstances. and on
either hemisphere. SO per cent OF the total heat
Of the year Is received during summer. 90 that
only the remaining 81 per cent Is left for
winter. It is manifest that the discovery OF
this law. far from shaking. signally fortines
the conclusions regarding the cause Of glacia-
mental assertion. modified by Sir Robert Balls
correction Of his error. will now appear In the
following much more emphatic form. viz. that
glacial conditions are those under which 90
Der cent OF the supply Of heat annually re-
cetved By . given hemisphere Is concentrated
into summer OF very short duration. while
the remaining 81 per cent Is spread over q
long and dreary winter Sir Robert Ball has
written this little book for the express purpose
Of bringing to general attention the great
Of the astronomical theory OF
glaciation BY his discovery OF the true law Of
the distribution OF heat