Rodolfo Amedeo Lanciani.

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The copper and iron wires in (8) were cut off fix>m the
lengths used in (2) ; but the wires used in (1) were taken from
parts of the coils removed fix)m the lengths (2) and (8). This
accounts for the close agreement of (2) and (8) and the higher
number obtained in (1).

My determination therefore appears to compare favorablv
with those made with different methods bv these experimental-
ists. I say *' appears," because although tne copper was of ex-
cellent quality and the iron the best procurable, yet they were
not chemically examined as to their purity.

Another series of determinations was ootained by comparing
the lengths of copper and of iron wires which would equal in
resistance one ana the same length of German silver wire, used
as a term of comparison. The result agreed with the above
determinations.

6. On a modification of the method.

As long ago as 1832 Faraday (Exp. Res. 170-180) first ob-
tained an electric current, direcfly inauced by the earth's mag-
netism, by rotating a closed wire circuit around an axis at right
angles '^ to the line of the dip ;" an experiment whose theoretic
beauty has ever been the admiration oi natural philosophers.

A len^h of 88 ft. of ^^ in. insulated copper wire was wound
into a coil of 8 ft. in diameter, containing 4 turns. The termi-
nals of this coil were connected by binding screws with the



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A. M, Mayer on measuring Electrical Conductivities. 317

wires leading to the galvanometer and the coil placed in a plane
at right angles to the line of the dipping needle. On quickly ro-
tating the coil through 180** the needles were deflected 26**, and
by making the rotations correspond in direction and time with
the oscillations of the needle, I found that six rotations brought
the deflection to over 46°. Faraday (Exp. Res. 202-218 and
8146 et seq.) has shown that the intensities of the magneto-elec-
tric currents induced in wires of diflferent metals are as their
electrical conductivities, therefore a coil of iron wire similar in
all respects to the above copper coil will give a deflection of
about 4** for the first rotation; but by increasing the number of
turns of the coil to 10 or more and by using a galvanometer
with a shorter and thicker wire coil, the angle of deflection can
no doubt be doubled.

The above &cts show that we can substitute for the steel
mamets, previously used, the magnetism of the earth, and can
replace the spirals by two similar coils made of the two speci-
mens of wire to be compared. The coils are placed on each
other so that their convolutions are in opposite airections ; and
having been firmly tied together their plane is made to coincide
with a direction at right angles to the dipping needle, while
their terminals are so connected with the galvanometer tiiat the
currents induced in the two coils tend to traverse it in opposite
directions.

Things being arranged as above, it is evident, — as the wire
coils are similar in all other respects, — that if the conductivities^
of the wires are the same, there will follow no deviation of th(^
galvanometer needle when the coils are quickly rotated through
180** ; but if the wire of one coil offers a greater or less resist-
ance than that of the other the needle will be deflected. B}'
ascertaining what differential actions correspond to known
differences of conductivity of coils of a certain diameter, num-
ber of turns and thickness of wire, we can, by always usin^^
similar coils in these relative measures, ascertain what difference
in relative conductivity corresponds to a certain angle of de-
flection ; the chords of these angles, or, the sines of half of the
angles, being te each other as the intensities of the currents.

Minute differences of resistance in the two coils may be made
to cause a deflection in the galvanometer needle by knowing
the time of its oscillation, and by reversing the motion of rota
tion of the coils so as to correspond to the swing of the needle ;
thus after several reversals a motion is given to the needle
which could not have been observed after a single rotation.

In point of ready application, — and especially in reference to
the determination of the resistances of lengthy conductors,— !
doubt whether this method will be generally adopted ; but afi;cr
the conception of the idea it appeared worth investigating ; this



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318 B. Broum en the supposed abaenoe of the

I have done, and have thus developed at least any yalue it may
possesa It certainly presented an interesting problem and the
pleasure afforded in its solution has repaid me for the consid-
erable labor which it required,
a Bethlehem, Pa., July 16, 1810.



Art. XXX. — On the supposed absence o/ffie Northern Drifi from
the Pacific Slope of the Bodcy Mountains; by Dr. BoBSBT
Brown, M.A., F.RG.S., etc, Edinburgh, Scotland.

Ik some interesting remarks addressed to the California
Academy of Sciences on the 4th of June, 1868, and published
in their * Proceedings * for that year (voL iii, pp. 271, 272), Pro-
fessor J. D. Whitney denies that there is any true Northern
Drift within the State of California. " Our detrital materials,"
the learned Professor remarks, " which often form deposits of
ffreat extent and thickness, are invariably found to have been
dependent for theu' origin and present position on causes simi-
lar to those now in action, and to have been deposited on the
flanks and at the bases of the nearest mountain ranges by cur-
rents of water rushing down their slopes. While we nave abun-
dant evidence of the former existence of extensive glaciers in
the Sierra Nevada, there is no reason to suppose that this ice
was to anv extent an effective agent in the transportation of
the superficial detritus now resting on the flanks of the moxm-
taina The glaciers were confined to the most elevated portions
of the mountains, and although the moraines which they have
left as evidences of their former extension are often large and
conspicuous, thev are insignificant in comparison with the
detntal masses formed by aqueous ax)sion. ITiere is noAing
anywhere in California which indicates a general glacial epoch dur-
ing which ice covered the whole country, and nuwed bodies of detri-
tus over the surface independently of its present configuration,
as is seen through the Northeastern States."

Mr. Whitney goes on to observe that the same condition of
things prevails m Nevada and Or^on, the detritus seeming
always to be accumulated at the base of the mountains. Fur-
ther, fix)m the observations of Messrs. Ashbumer and Dall, he
lemarks that "it would appear that no evidences of a North-
em Drift have yet been detected on this (Pacific) coast, even as
Jar north as British Columbia and Russian America (Alaska).
Neither of these gentlemen has observed any indication of a
transportation of orift materials from the north toward the south,
or any condition of things similar to that which must have
existed in the Eastern States during the diluvial epoch." Mr,



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Ntn'thern IMft Jrtym ih£ Rocky M(mntm 819

W. H. Dall, the gentleman referred to in the foregoing .extract,
(and well known to the readers of this Journal as one of the
most active and observant of the staff of Naturalists attached
to the Collins Overland Telegraph Expedition), follows suit to
these observations of Professor Whitney by declaring, in a

Eaper published in this Journal for January, 1868, that though
e had carefully examined the country over which he had
passed, in Alaska, for glacial indications, he had not found any
effects attributable to such agenciea His own opinion, indeed,
fh)m what he had seen of the west coast, though yet unproved^
was that the glacier-field never extended in these r^ons to the
westward of the Rocky Mountains, though single gmciers have
existed and still exist between spurs of the mountains which
approach the coast No boulders, according to Mr. Dall, such as
are common in New England, no scratches or other marks of
ice action had been observed by any of his party, though care-
fully looked for.

It is this general theory of the absence of the Northern Drift
in Northwestern America that I propose combating in the re-
marks which follow, and I do so with extreme diffidence, know-
ing well fh)m old experience the care and caution with which
Prof Whitney has proceeded in his remarkable geological sur-
vey of California, as well as in his earlier work on the shores of
Lake Superior. For this reason I wiU speak only of what I
know from personal knowledge of the distncts visited by myself,
calling in, however, the observations of others as corroboration
of my statements.

As fer ■ as Alaska and California, and even Oregon and
Washington Territory, are concerned, I must leave uie ques-
tion of glacial remams within their bc»undaries, to observers
more intimately acquainted with their country than I am, though
I have a strong inclination to believe that what I say about
other portions of the Pacific coast will hold eaually ffood regard-
ing them also. I have certainly visited and traveled through
Cdifomia, and have been in some portions both of Oregon and
Washington Territory, and on the borders of Alaska, yet my
knowledge of these countries does not entitle me to dispute
statements so explicitly made by such excellent observers as
those cited. But with the coast of British Columbia and the
whole of Vancouver Island I am very intimately acquainted —
perhaps more intimately than any other single individual —
and can speak positively r^arding the marked presence of
true Northern Drift there, so that with every respect to the
opinion of so distinguished a geologist as Prof Whitney, I am
compelled to dissent from his theory regarding the entire ab-
sence of glacial remains proper, from the Pacific slope of the
Rocky Mountains.



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320. B. Brown on the supposed absence of the

Between 1868 and 1866 — ^nearly four years — ^I traveled on
foot and in canoes, through the forests, over the monntams, on
the rivers, the lakes and the prairies of the whole of the rwon
indicated, as Commander and Government Agent of the First
Vancouver Exploring Expedition, and as Botanist of the Brit-
ish Columbia Expedition. Again I have three times visited
the Arctic Regions, passing a whole summer in Greenland,
studying these and other similar phenomena, and have for many
years been very familiar with the remains of the Northern Drift
m Scotland, the north of England and portions of the north of
Europe. These personal particulars are mentioned to show
that I am in a position to know glacial remains when found,
and to distinguish them fix)m the ordinary terrestrial debris ac-
cumulated by causes now in action in the temperate countries
where formea The result of these extended ooservations has,
therefore, been to confirm me in an opinion entirely contrary to
that expressed by Messra Whitney, Ashbumer and Dall, viz :
that so far from the Northern Drift being absent from Vancou-
ver Island and British Columbia, it is present in as marked a
manner as ever I saw it in countries celebrated for the presence
of such remaina This opinion I casually expressed in 1869 in
a memoir entitled Das Innere der Vancouver insel^ published in
the volumes of Petermann^s Qeographische Mittheilunaen for that
year, and more recently and more explicitly, in another. On the
Physical Characteristics and Geographical IHstribution of the Coal
Fields of Northwest America (Transactions of the Geological So-
ciety of Edinburgh, 1868-69). As that statement has been in-
clined to be called in question — scientific sceptics not unreason-
ably considering that a doctrine promulgated by so eminent a
geologist as Prof Whitney is entitled to fiirther consideration,
man a mere curt denial of its truth, I have considered it proper
to present in a concise manner in this place the fects on which
I base my disbelief in its truth. As early as 1860, Mr. Henry
Bauermann, geologist of the British Northwest Boundary Com-
mission, made many observations on this subject ; and subse-
quently, in 1862, in a Prize Essay on Vancouver Island^ its resour-
ces and capabilities as a Colony (Victoria, 1862), Dt. Charles
Forbes, RN., published similar fiicts, which my own researches
have only tended to confirm and enlarge, over a greater area.
Dr. Forbes showed, what is familiar to every one visiting that
section, that in the whole southern portion of the Island, mough
from the open prairie-like character of some portions of ike
southeastern section it is there earlier observed than in the
wooded districts, the scooping, grooving, and scratching of the
rocks by ice action is very marked. The chief rock m situ
there is a dense, hard, feldspathic trap, and this is ploughed in
many places into ftirrows six to eight inches deep, and &om six



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Northern Drift from Hie Bocky Mountains. 821

to eighteen inclies wide. The ice action is also well shown in
the Siarp peaks of the erupted, intruded rocks, having been
broken oS and the surface smoothed and polished, as well as
grooved and furrowed, by the ice action on a sinking land, giv-
ing to the numerous promontories and outlying islands which
here stud the coast, tne appearance of rounded bosses between
which the soil is found to be composed of sedimentary alluvial
deposits, containing the debris of tertiary and recent shelly
beaches, which have, after a period of depression, been again
elevated to form dry land, and to give the present aspect to the
physical geography of Vancouver Island.

The whole surface of the country is strewn with erratic boul-
ders. Great masses of 60 to 100 tons in weight, — chiefly of
various igneous and crystalline, as well as sedimentary rocks,
sufficiently hard to bear transportation, — are found scattered
everywhere over the island from north to south, and through
the region lying on the western slope of the Cascade Moun-
tains. Some of these syenitic or granitic boulders are of a fine
grain and accordingly some of the chief buildings in Victoria
are built from them. I am not aware that any rock of a simi-
lar description is found in situ anywhere in Vancouver Island;
it appears to have drifted in icebergs fipom the nortL I am
confiaUy of opinion with Dr. Forbes, that though the last up-
heaval of the land, which might have taken place at a geologi-
cally recent period, failed to connect Vancouver Island with
the mainland of North America ; it was at all events sufficient
to effect to a great extent, the junction of numerous insular
ridges, and thus to form a connected whole of what vxis^ and
might have continued to be, only an archipelago of scattered
islet& The upheaving force elevated and connected these and
brought to the surface, the great clay, gravel and sand deposits
of the northern Drift which nad swept over, and been deposited
on, the submerged land. These sands, gravels and clays, were
now to form the soil of land, prepared for the habitation of naan.
These constituents of the drift remain, in many parts, thinly
covered by a coating of vegetable mould ; but much has been
washed away. The clay remains most generally and widely
spread out, as a retentive sub-soil, having resting upon it a thick
coating of v^etable mould. The most valuable soil is found
sweeping down the sides of gentle slopes, filling up hollows and
swampy bottoms, and, mixed with the rich alluvial deposits of
such districts as Saanich, Cowitchan, Delta of Nanaimo, and
Comax, forms an inexhaustible source of agricultural wealth.
The true glacial or boulder clay is found in various portions of
Vancouver Island. Bauermann has described it as seen near
Victoria, and I am glad to be able to vouch for the correctness
of his description: it is extensively developed not only there



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822 B. Broion <m the supposed abdence of the

but on the opposite coasts of Washington Territoiy and British
Columbia, in the neighborhood of Esauimault and Victoria,
the rocks are deeply scored and groovea along the shore, and
large boulders are scattered irr^ularly over the surfiEu^ of the
country, as already described. The other rocks observed as
erratics were black cherty conglomerate, similar to that under-
lying the secondmes,* dark laminated mica schist with well
defined garnet-crystals, hornblende rock and largely crystaUine
greenstone, and rarely and in small masses vesicular obsidian
and pitchstoncL

The following section is given to show the general character
of the drift, at Esquimatdt Harbor.

Black saodj and peaty ground with brdcen shells 2 lo6 feai

YeUowish sandy day with oasts of sheila (Oardium and Mya) and a few

pebbles and boulders 6I08 **

Oravel of scratched pebbles resting on rock 2 to3 **

The rocks are grooved and scratched at the junction ; the di-
rection of the g&cial markings is between N.-S. and N.N.W-
S.S.E. In a well sinking at Esquimault Barracks (for the
boundary Commission) the lower gravel was reached at 42 feet,
after going through a sandy blue clay without shells or boul-
dera The section in tiie cuff between Albert Head and Esqui-
mault is as follows : —

Blue drift day with boulders ; junction with rode not seen, 70 feet

Fine sand and gravel, passing upward into coarse quartzose gravel, 100-120 ^
— Qwirt J&wik ofl/md, OeoL Soe.^ 1860, p. 202.

Mr. Bauermann is, or at least was, at the period his observa-
tions were made, a member of the Geological Survey of the
British Islands, and therefore might be supposed to know what
he was speaking about I say so because though I have been
able to confirm all his descriptions, yet it is satisfactory in a
subject of controversy involving so many important matters to
have the support of an additional qualified witness.

As already remarked, I cannot speak so confidently of Wash-
ington Territory, Or^on, and the mterior of British Columbia
to the east of the Cascade Mountains, being less familiar widi
that section of the Pacific slopa However, through western
Oregon wherever I visited the country, down at least to the
Umpqua river, and in Washington Territoiy to the very base
of tne Cascades, whatever Airther, I observed glacial remains
not less marked than in the neighboring region of Vancou-
ver Island. Some of the erratic blocks are scattered over
the prairies of that region, standing on the stoneless grassv
plains in marked contrast to their surroundings. These boul-

* *' Tertiarics," Mr. Bauermann says, but if he refers to the Northern coal flelHs
of the island, then tiiere can be but little doubt that these beds are as I have giren
them, here aod elsewhere, of secondary age.



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Northern Drift from the Bocky Mountains. 823

ders and erratic blocks* have even attracted the notice of the In-
dians—otherwise so stolid in regard to the natural objects among
which thej liva One huge angular block, on the Snoqualami
Prairie, has a tradition attached to it, to the effect that at one
time it was suspended from the sky but was cast adrift to earth
on account of tne wrath of the Supreme Being, being roused at
the licentiousness of a minor god and his myrmidons who for the
time being were disporting themselves on it I Not fer from the
comer of the Peninsula of Saanich off the coast of Vancouver's
Island, there are several large boulders — (apparentlv rounded by
the waves and not by ice action ?) which aborigmal tradition
assert to have been some old witcnes turned into stone. My
canoe-men in passing them used not unfrequently to stop there,
and throw water on them, shouting : " Give us a wind, you old
jade !" and as occasionally an afternoon breeze does not spring
up in that region after the midday summer calms, the supersti-
tion obtained with them a semblance of belief, and so got handed
on to posterity clothed in all the hoary sanctity of antiquity.

Groovings and other unequivocal marks of aeneral ice action
are not wanting in Washington Territory either. Even with
the superficial glance we were enabled to give the subject in
hurried journeys over that region, for other purposes, we observ-
ed not a few of such deep unmistakable ice planings. And in
a note received recently from my friend and former traveling
companion, Mr. Edmund T. Coleman, (well known as the author
of the folio " Scenes from the Snow Fields of Mont Blanc," and
who may therefore be supposed to know ice markings) he states,
though with no view to combating the theory in hand, which
indeed he knew nothing about : —

" I saw at Seahome ^^ear Bellingham BayJ in the cuttings
made for a tramway, the finest instances of fluting and groov-
ing, evidences of glacial action, that I have ever seen on this
coast They were 90 feet in length, running N. and S. accord-
ing to the theory of Professor Agassiz."

I have not been in Alaska proper, but in 1866 in a visit to
the Queen Charlotte Islands lyinff some thirty or forty miles off
the northern coast of British Columbia, close to the southern
boundary of the former territory,f marks of the northern Drift
quite as marked as in Vancouver's Island were found there.

Indeed in crossing the " spit " at the entrance of Skidegate

* By " boulders " I mean to designate rounded worn blocks of stone carried
along in the fryoraAM frofonde of tlie ice sheet; bj " erratic blocks,** angular fhig*
ments of rook, apparently oonveyed to their present resting place in ice (field ioe
or bergs) without having been subject to erosion. The necessity of the division is
apparent The first is very rare on the Pacific coasts and I suspect part of local
moraines; the other is universal

J I have described their geography in the Proceedings of the Boyal Gkograph-
Sodety of London, for 1869. Some remarks on their geology will likewise be
found in the same place.



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82-t Ji. Brown on ike supposed absence, etc.

Sound, we had a dangerous reminder of the fact, having lost
the keel of our schooner, on one of the great boulders which
cover that locality. Masset Spit and other shoal localities are
equally dangerous on that account Here they present them-
selves disagreeably to the seaman's senses, but on land, though
less visible on account of the dense vegetation concealing th^n,
yet to one accustomed to search for such things, traveled blocks
and ice groovings are sufficiently abundant Boulder clay is
also not wanting to complete the tale of the glacial period in
Northwest America.

All throughout this paper I have sedulously avoided touch-
ing upon the modem local glaciers which are found scattered
all throughout the northern portion of the Cascade and Coast
Ranges of Mountains, in some places (as in some of the north-
ern inlets on the coast of British Columbia) approaching to
within a short distance of the sea ; and in the southern part of
the latter range they are found in most of the high mountains,
such as Mt Baker, Diamond Peak, etc. Li another place, " On
the formation of Fjords, etc."* I have shown that in all likelihood
these British Columbian inlets were at one time the site of gla-
ciers, and though the marks of local glaciers are evident here and
there where none are now found, vet the appearances d^cribed
are due to a totally diflferent set or causes fix)m these, or any now
in existence on the American continent, unless indeed Green-
land be included under. that geographical division. These local
glaciers in the limits assigned to a paper of this nature do not
therefore require to be further touched upon.

Am I therefore in error, when I think that the case I have
submitted, makes good the thesis with which I commenced
these remarks, viz : — that whatever may be said of California
and Alaska (and Messrs. Whitney and Dall are quite capable
of holding their own in reference to their assertions about these
regions), the Northern drift is certainly not absent from Brit-
ish Columbia, Vancouver's Island, Washington Territory and
the Queen Charlotte Islands? With every respect to the ob-
servations of the gentlemen named, my more extended oppor-
tunities of investigation have, I think, enabled me to answer,
with some degree of certainty, this question in the n^ativa
Perhaps I would not have been so particular in discussing this
question at length, had not Prof Whitney's and Mr. Ball's idea
been taken up in this countiy, and in America by geologists of
no mean emmence,f and a disposition been shown by others
less capable to build thereon theories, where no theories ought
to be built

4 Oladstone Terrace, Hope Park, Edinburgh, June 2Sd, 1870.



Online LibraryRodolfo Amedeo LancianiThe American journal of science and arts → online text (page 90 of 109)