Rodolfo Amedeo Lanciani.

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hemisphere occurs in periheho; then

the Northern hemisphere will have a mild winter and cool summery
the SoiUhem hemisphere will have a cold winter and hot summer.

So far (granting Mr. Croll's astronomical data, for which he cites
Leverrier, and which I believe are indisputable) there is no room
for doubt. I have now to discuss the question, what effect these
diversities of climate will have in producing glaciation.

Mr. Croll thinks the hemisphere of ooldtointer will be the gla-
ciated one. I think, on the contrary, the hemisphere of cool summer^
will be the glaciated one.

On this subject it is needless to attempt to make any deduction
from theory. We have plenty of observed data ; and I think I can
show that they all go to prove a cool summer to be what most pro-
motes glaciation, while a cold winter has, usually, no effect on it
whatever.

Forbes, in his work on Norway and its Glaciers, p. 206, quotes
^the excellent generalization of von Buch, that it is the tempera-
ture of the summer months which determines the plane of perpetual
snow." This indeed is almost an identical proposition ; for per-
petual snow is snow that lies through the heats of summer ; and



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116



Scientific Intelligence,



it would appear obvious enough, had it not been frequently over-
looked, that it must be the temperature of summer which, other
things being equal, determines the level of summer snow.

But, according to the same authoritv (Forbes's * Norway and its
Glaciers,' p. 206), " another cause affecting exceedingly the level
of the snow-line is the amount of snow which falls.'*

These laws are illustrated in detail by the following table. In
constructing it I have assumed, what is tolerably near the truth,
that the temperature of the hottest month of the. year decreases in
ascending at the rate of 1** F. for every 300 feet. The tempera-
tures are taken, as accurately as I have been able to do it, from
Dove's map. My authorities for the heights of the snow-line are,
for the first four, Durocher as quoted by Mr. Hopkins in the
* Proceedings of the Geological Society' for Dec. 17, 1861, f<>r the
rest, Mrs. Somerville's ' Physical Geography,' p. 314. The tem-
peratures are in degrees of Fahrenheit. The heights are in feet.

Temperature of Height of 82> "amxa^xtnt

liot6ett month F. In hottest J^Sl^hSr

at sea level. month. inow-llne.

Pyrenees 74 6 12750 9300

Caucasus 77 13500 10300

Mont Blanc 72-5 12150 9000

Bernese Alps 72-5 12150 8800

Scandinavian Fjelde, 61^ 43' N 59 8100 5600

Mageroe, Norway, extreme north 45 '5 4050 2160

Himalaya, about 31° N., north side 83-76 15525 16620

The same, " south side 83*75 15525 12980

Andes, near Quito 7926 14176 15796

. " 18° N 81-5 14850 14772

" near Valparaiso 68 10800 12780

" 37° 40*8 63-5 9450 7960

Straits of Magellan 46*5 4050 3390

It is evident by this table that the snow-line rises above the line
of 32° for the hottest month of the year where the snow-fall is small,
and sinks below it where the snow-fall is great. In the Caucasus,
the Alps, and the Pyrenees, the snow-line is about three-fourths of
the height of the line of 32° for the hottest month of the year ; in
the Fjelde of Norway, about two-thirds; in the Peruvian and
Chilian Andes above, but in Patagonia and Tierra del Fuego below ;
above, on the north side of the Himalaya, but below on the south
side. These contrasts are all to be explained by the difference in
the amount of snow-fall, which is greater on the south than on the
north side of the Himalaya, greater in Patagonia and Tierra del
Fuego than in Chil6 and Peru, and probably greater, at least in
winter, in Norway than in Central, Southern, or Eastern Europe,

The dependence of the height of the snow-line on summer tem-
perature and on amount of snow-fall, to the exclusion of winter
temperature, may be best shown, perhaps, by two extreme cases.
The mean temperature of the Altai mountains (according to Mr.
Hopkin's paper cited above) is below freezing ; yet in consequence
of the comparatively warm summer, and the small snow-fall, the



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Mineralogy and Geology, 117

height of the snow-line (Mrs. Somerville's * Physical Geography,'
p. 61) is about 6000 feet. On the Straits of Magellan, on the con-
trary, though the mean temperature is several degrees above
freezing, the height of the snow-line (see table) is little more than
half as much.

It is well known that, other things being equal, the magnitude
of glaciers depends on that of the snow-fields in which they rise ;
and a-s of course any depression of the snow-line will enlarge the
snow-field, it follows that the lower the snow-line the further will
the glaciers descend below it. As a decrease of about 3o F. is due
to every 1000 feet of ascent in the hottest month, it follows that a
fall of temperature to that extent in the hottest month would '
lower the snow-line by about 1000 feet; and in many cases it is
likely that the glaciers in such a case would descend 1000 feet fur-
ther below the snow-line than atpresent, thus gaining a total
increase of 2000 feet of descent. This might not have much effect
on the climate of Central Europe, but it would have a very great
effect in those high latitudes where the glaciers would reach the
sea and give origin to icebergs ; for we know that icebergs have
great influence as transporters of cold.

In particular cases the effect of a comparatively slight fall of
summer temperature would be very great. I quote from Forbes'
* Norway and its Glaciers,' p. 216 : —

** Though the surface actually covered by perpetual snow in Nor-
way be small, yet the mountainous districts and tablelands every-
where approach it so nearly that the snow-plane may be said to
hover over the peninsula, and any cause which should lower it even
a little would plunge a great part of the country under a mantle
of frost."

And again, p. 243 : —

" It is exceeaingly probable that a diminution of the temperature
of the summer months by 4° only would at once place one-fowrth
of the surface of Norway within the snow-line; and so vast amass
of snow would refrigerate the climate, especially the summer tem-
perature, to such a degree as would unquestionably pour glaciers
mto the head of every fiord in western Norway. . . , The
lowering of the snow-hne over so large a surface would deteriorate
the climate and lower the mean temperature, which would lower
the snow-line still further."

The change in the eccentricity of the earth's orbit is in all proba-
bility amply sufficient to account for this or a much greater change
in summer temperature.

I take the following data from Mr. CroU's paper. The recently
ascertained error in the old determinations of the sun's distance
affects both distances alike, and consequently does not affect their
ratio. Along with the maximum distances of the sun at present
and at greatest eccentricity, I state the proportionate quantities of
heat the earth will receive under those two mfferent conditions : —

Ban*B mftzimum Bfttio of heat

distance. received.

At present 96,473,206 miles .... 1 00

At greatest eccentricity. . 102,256,873 " .... 90



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118 Scientific Intelligence,

So that in the one case the earth receives about one-tenth less heat
than in the other.

The sun's maximum distance occurs at present a little after the
midsummer of the northern hemisphere. When it occurred at the
same time of the year during the period of greatest eccentricity,
the earth at our midsummer was receiving only nine-tenths of the
quantity of heat which it now receives at that time of the year. I
cannot calculate the effect on climate ; but it must have been very
great, not only directlv, by depressing the snow-line, but as Forbes
remarks in the place cited above, indirectly by chilling the air — and
I will add, by nlling the North Sea with the icebergs which must
have broken off from the glaciers that filled the Norwegian fiords,
as they do now from the glaciers of Greenland- We have plenty
of evidence of iceberg action during the glacial period.

I believe I have shown that glaciation depends chiefly on a cold
summer, but partly also on an abundant snow-fall. I have now
to show that a period of cold summers, caused as I have explained,
must be also one of snowy winters ; so that the two conditions
favorable to glaciation will occur together.

During the mild winter of the glaciated hemisphere, there is a
hot summer in the opposite one. Increase of temperature promotes
increase of evaporation in a much greater ratio than that of the
increase of temperature ; and increased evaporation in the summer
hemisphere will produce increased snow-fall in the winter one.
We know that at present the vapor raised in one hemisphere is
to a great extent precipitated in the other ; for, were it not so, the
southern hemisphere, by reason of its greater extent of ocean sur-
face, would have a rainier climate than the northern : and such does
not appear to be the case on the whole. Besides, during a glacial
period, the atmospheric circulation between the two hemispheres,
at the time of the earth's minimum distance from the sun (which
on my theory was in the winter of the glaciated hemisphere), must
be more active than ever it is now ; for when the earth, at either
solstice, was nearer the sun than is ever the case now, and the
difference of temperature between the two hemispheres conse-
quently at its greatest possible amount, this would produce a very
active circulation of atmospheric currents between the two hemi-
spheres, which would involve the deposition as rain or snow in
the winter hemisphere of a great part of the moisture evaporated
in the summer one.

[The author continues with remarks on fiords as results of the
Glacial era, a subject long since discussed in this Journal.]

3. Oeological tteport of the exploration of the Yellotostone and
Missouri Rivers ; by Pr. F. v . Haydbn, Assistant under the
direction of Captain (now Lieut. Col. and Brevet Brig, Gen.)
W. F. Reynolds, Corps of Engineers, 1859-60, with a colored
map. 174 pp. 8vo. 1869. — Several years have elapsed since the
explorations for this report were made, and many of its general
conclusions have appeared, through the author, in this JoumaL
The details here presented will be read with much interest. The



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Mineralogy and OeoJogy. 119

map is large and very instructive, showing, more accurately than
had been done before, the distribution of the Tertiary and Creta-
ceous formations, and the girt of Carboniferous and Potsdam rocks
around the high metamorphic ridges of the summit. Some fur-
ther explorations of the mountains are required to make certain
all the points in this distribution.

'ITie last thirty pages of the volume are occupied by a report on
the Cretaceous and Tertiary plants of the i-egion, by Dr. J. S. New-
berry, now Professor of Geology and Paleontology in the School
of Mines, Columbia College, New York. Dr. Newberry's exten-
sive knowledge of the fossil Botany of North America has enabled
him to ffive his memoir great value. Dr. Hay den's absence in the
mountains, during the past year, while his report was in press,
accounts for its many typographical errors.

In the exploration of last year here referred to. Dr. Hayden was
engaged in a new Government Survey under the direction of the
Department of the Interior ; and the first pages of the " Prelimin-
ary Field Report of the Survey " have been received by us. The
Report promises to be one of great value to the science, and a notice
of its results may be looked for in our next number. The Hon.
T. D. Cox, Secretary of the Interior, states in his annual Report for
the year 1869, that " Dr. Hayden entered on his labors in the field
the last of June, at Cheyenne, Wyoming Territory. His route was
through Denver, the silver and gold mining region of Georgetown
and Central City, the^ Middle Pane, Colorado City, and Fort Union
to Santa F6, returning through the San Luis Valley and South Park
to Denver. The exploration, though brief and rapid, was eminently
success^, and the collections in geology, mineralogy, botany, and
zoology were extensive. His preliminary report bears date Oct. 16.
It is accompanied by two other reports made to him by his assist-
ants—one on mines and raining, tne other on agriculture. These
papers are a valuable contribution to our knowledge of the subjects
which they embrace, and merit careful perusaL"

4. Mineralogy Ulustrated; by Dr. J. G. v. Kurr, Prof. Roy.
Polytechn. School at Stuttgart, etc. 22 large colored plates inter-
leaved with explanatory text. — The figures m this Atlas represent
in colors crystals or massive specimens of various minerals, espe-
cially the ornamental species, and is intended to aid the student in
their identification. The figures are in general well colored ; and
although the text is not wholly free from its German idiom, the
work may be of value in the study of the science.

6. Tableau Mineralogique ; by M. Adam, Commancfer de la
Legion d'Honneur, etc. 102 pp. 4to. Paris, 1869. — ^A classified cata-
logue of the minerals in the splendid collection of Mr. Adam, of
Paris, with a brief statement of the character and composition of
the species.



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120 Scientific Intelligence.

nL BOTANY AKD ZOOLOGY.

1. Botanical NotahUia. — Some annooncements of recent publica-
tions with cursory remarks, and items of intelligence are here
brought together m the expectation that they may be interesting
or useful to botanical readers of the Journal The only one of
the publications here mentioned which can be said to possess much
general interest is the first, viz :

An Address of George BerUham^ Esq.y Preside/nt of the lAnncean
Society^ London^ read at the Anniversary Meeting, May 24, 1869.
It is the latest one of that series of pertinent annual discourses by
which Mr. Bentham's presidency has oeen distinguished, and which
it is hoped he will continue. A preceding one was reprinted in
this Journal, and it would be well that this should be also. The
topic is Geographical Biology^ considered first for plants and then
more succinctly for animals. Although distribution is one of the
strongest points of derivative doctrine, yet it is wonderful to see,
in the light of this sober and impartial survey, how entirely the
whole aspect of philosophical natural history in this regard has
changed within two decades. " Centres of creation," and the like
are of the language of the past, here replaced by Bentham^s hap-
py term of " areas of preservation." And the conclusion, tardily
reached ^' that the present geographical distribution of plants was
in most instances a derivative one, altered from a very different
former distribution," has been followed by the conviction that the
present species themselves are equally derivative, and have a
changeful history, some steps in which may be dimly surmised by
the study of cognate forms, extant or fossil At the point now
reached, if not by general yet by lar^e consent, the problems we
are led to consider are such, that it is indispensable to have a
term of wider application than " species " technically means ; and
Mr. Bentham here appropriates to this use the word Race^ to de-
note either permanent variety (the old meaning of the word
when definitely restricted), or species, or groups of two or more
near and sooalled representative species, I e., for those collections
of individuals or resembling groups of individuals whose associa-
tion in the way of lineage is taken for granted by this class — or
rather by these classes — of naturalists. As the term was only be-
ginning to get fixity in its restricted sense, it will take the
wider sens e without confusion or difficulty, and with the advantage
of a vernacular instead of a new-coined purely technical word.

The Miscellaneous Botanical Works of JKobert Broton^ which
Mr. Bennett has edited for the Ray Society (2 vols. 8vo), are now
completed by the Atlas of Plates, in small folio, 38 plates. The
best thanks of Botanists, especially of the younger ones, are due
to Mr. Bennett and to the Council of the Ray Society.

Another publication hj the Ray Society for which botanists
will be grateful is the Vegetable Teratology^ an Account of the
principal Derivations from the itsual construction of Plants j by
Dr. Masters. It was published last autumn, and forms an 8vo
V olume of nearly 600 pages, illustrated by over 200 wood-cuts.



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Botany and Zoology, 121

The coliection of cases is ample, the arrangement clear and scien-
tific, and the general handling of morphological questions and the-
ories of structure shows a full acquaintance with the subject. One
cannot here well advert to points which invite discussion or further
remark. Indeed a treatise of this character and upon such topics
ought to be reviewed in extenso. It should be observed in pass-
ing that it may not be quite correct to speak of DeCandolle as " giv-
ing in his adhesion to the morphological hypothesis of Goethe (p.
xxii, also p. 476) : it is generally understood that when the Thiorie
JElhmintaire and the Organographie were written DeCandolle knew
nothing of Goethe's essay, and had never heard oi Wolff.

A memoir of the Life of the late Prof Wm, H. Harvey ^ prin-
cipally made up of his own inimitable letters, edited by a surviving
relative, has lately been published by Bell and Dalby, London. The
book was at first intended for private distribution ; but it was well
decided, as his many friends and admirers in this country will be
glad to know, that it should be issued through a publisher in the
usual way. It makes an octavo volume of goodly size. Such a
charming photograph of a lovely character will interest many to
whom Dr. Harvey was personally unknown.

The Genera of South African Plants was one of the late Dr.
Harvey's first undertakings when established, it was thought for
some years, at the Cape of Good Hope. It was published at Cape
Town, in 1838, and most useful it was in inspiring and developing
the Btudv of Botany in the Colony : nor is its usefulness superseded
by the elaborate P^^lora Capeneie^ which was carried on with re-
markable promptitude while Dr. Harvey Uved, but which remains
unfinished. He had prepared in a good degree the materiab for a
new edition of the Genera, which has i ow been edited by Dr.
Hooker, the succinct introduction to Botany originally prepared
by Mr. Bentham for his British Flora, and since added to all the
Colonial Floras, being prefixed.

As to these Colonial Floras, that of Australia is pushed forward
with Mr. Bentham's customary vigor, under the great advantage
of his unsuipassed knowledge and his enviable opportunity of be-
ing able to devote his whole time without distraction to Systematic
Botany. The fourth volume of the Flora Avstraliensis appeared
almost 2^ year ago: it contains most of the Monopetalous orders
after the Compositae^ excepting VerheruiceoB^ LoMatce^ ifec, which
are probably already in type for the fifth volume. Under Breweria
Mr. Bentham justly remarks that this genus ought not to have
been referred to Bonamia of Madagascar, as I had rashly done ;
yet he is wrong in the supposition that Thenars' ^ant^not Convol-
vulaceous, but allied to JEhretia and Cordia, On inspection it
proves to differ from Breweria^ and to agree with Cressa, in the
corolla, which not plaited in aestivation. There are probably two
species.

The Mora of Tropical Africa by Prof. Oliver, ** assisted by
other botanists," though not exactly a Colonial Flora, is upon the
same model It is founded upon the African collections which
have accumulated at Kew. Considerable as they are already, they



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122 Scientific Intelligence.

represent the vegetation only of the outskirts of a vast terra inr
cognita, of which we may hope to know something ere long, and
which may give to this work as it advances an exceeding inter-
est. This first volume, which was published in 1868, includes the
ordera antecedent to Leguminoece, The McUvaceoe and their allies
are by Dr. Masters, who has paid much attention to the structure
of the flowers of this group ; the AmpelidecBy Sapindaceoe and
ConnaracecB are by Mr. Baker.

Dr. Oliver has just published a neat little First Book of BicUan
Botany^ on the basis of his well-known elementary Lessons for
home use, only the illustrations of the natural orders, the exam-
ples, <fec., are from Indian plants, and considered in view of Indian
feotany.

The ninth part of Dr. Seemann's Flora Vitiensis^ nearly con-
cluding the Phanerogamia, has been for some time issued ; and
the lOtb, which will complete this laborious work, is in press.
The Ferns are by Dr. Oaruthers of the British Museum, so favora-
bly known for his researches in fossil botany.

Mr. Baker, the Assistant Curater of the Kew Herbarium, after
comjpleting the Synopsis Filicum which was barely conunenced by
Sir Wm. Hooker, has made the results of that work the basis of a
very interesting paper On the Geographical BistribtUion of Ferns,
in the last (26th) volume of the Transactions of the LinnaBan
Society.

The publication of Sir Wm. Hooker's Icones JPiantarum closed a
dozen years ago with the 10th volume, completing a thousand
plates. Dr. Hooker with the assistance of Mr. Bentham and Pro£
Oliver, has now commenced a third series, of which two parts are
issued, one in November, 1867, the other in June, 1868, and a
third part is in press. The plates are numbered on from volume 10
(which is a convenience in citation) yvz: 1001 to 1050. They are
taken from plants in the Kew Herbarium, and will serve to illus-
trate some of the work going on in that richest of botanical collec-
tions, and notably, as it proceeds, the Genera JPlantarum, Thus
far nearly all are from the southern hemisphere. Two plants, how-
ever, are Xorth American, viz : Arceuthooium brachypodtim of En-
gelmann, from New Mexico, in which Prof. Oliver directs attention
to some apparent peculiarity of the ovule, which needs investiga-
tion in the fresh plant ; and Zeitneria Floridana of Chapman,
which Prof Oliver describes as having a thin but evident layer of
albumen around the embryo, and he agrees with Chapman in refer-
ring the genus to Myric(zcece^ although with misgivings.

A whole volume of the Journal of the lAnnoean Society (the
twelfth, issued in advance of the eleventh), is occupied with an
enumeration and description of all known Mosses of South
America, by Mr. Mitten, rounded primarily on Sprufce's collections,
which have been distributed into sets and disposed of Mitten's
Mvsci Austro-Americani thus forms a substantial 8vo volume of
650 pages. A double number of the eleventh volume is equally
devoted to Mr. Spruce's South American collection^ and researches,
viz., to the PalmcB AmazoniccB, an account by himself of the



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Botany and Zoology. 12S

Pabns of the regions yisited by him, a paper rich in generally
interesting and readable as well as technical scientific matter.

Dr. Anderson has a paper on the Palms of Sikkin in the preced-
ing number of the same volume ; Dr. Kirk writes on the Copal of
Zanzibar, and makes out that the old or fossil copal is the produce
of the same tree, a species of TVac/iylobium from which recent
Zanzibar copal is at present yielded. The other articles most note-
worthy for us in the eleventh and the later numbers of the tenth
volumes, are one by A. W. Bennett of London on the Sti^ucture
cmd Affinities of Pama8$ia^ upon which there is somewhat to be
said whenever the present writer has opportunity to make re-
examinations in the view of correcting certain probable mis-
takes or oversight. On chemical reaction as a specific character
in Lichens^ by Dr. Lauder Lindsay, who comes to the conclusion
that these chemical tests introduced of late are of little value or
reliability. Notes on Jttssima by Charles Wright, a letter to Dr.
Hooker, showing what excellent characters, hitherto nearly over-
looked or in some cases misapprehended, are furnished by the seeds,
&c., in this genus: and finally Fungi Cubenses, Dy Messrs:
Berkeley and Curtis, founded on the very ample and largely novel
collections in this order made by Mr. Charles Wright It is to be
stated here that these Ftngi, accurately determined by the above
distingnished mycologists, have now been distributed into sets,
and placed on sale. Application for the few remaining sets may
be made by letter to Mr. Wright, at the Harvard University Hei^



Online LibraryRodolfo Amedeo LancianiThe American journal of science and arts → online text (page 15 of 109)