178 
that the higher portions of the ridges tend to rise to a 
certain level, which, on being connected by an imaginary 
plane, form a gently-sloping surface over a considerable 
area, it may be of hundreds or thousands of square miles 
in extent. Now, if in addition to this we insert the strati- 
fication of the district crossed by the section, and taken 
trom actual observation, it will often be found that this 
imaginary plane is formed of the truncated edges of 
highly-inclined strata, or of the denuded summits of anti- 
clinal arches of contorted or folded strata. When such 
strata are of hard and tough materials it is clear that they 
must have been planed down by an agent of great power and 
of long-continued action, but the result has been to convert 
originally highly uneven surfaces of flexured strata into 
approximately horizontal surfaces, over which inequalities 
have been worn off. Through such planes the existing 
river-valleys have been cut down, but between neighbour- 
ing valleys there is to be found the intervening ridge, 
trending upwards to the original, now imaginary plane. 
The Silurian district of Central Wales offers a remarkable 
example, which has been used by Prof. Ramsay (“ Mem. 
Geol. Survey,’ vol. i.). Let any one on reaching the 
summit of one of the long ridges to the south of Cader 
Idris place his head on the ground, and in this position 
survey the tract of hilly country lying to the southwards, 
and he will realise the nature of the plane surface, out of 
which the valleys have been hollowed. But there are 
many more remarkable instances even than this. The 
central plain of Ireland is an example on a larger scale, 
over which the Middle and Upper Carboniferous rocks 
have been swept away, leaving a floor of limestone ; but 
it would be impossible to explain the course of its great 
river, the Shannon, without referring its origin to a time 
when a sloping plain stretched from the present sources 
of that river amongst the Leitrim Hills to Shannon harbour 
below Limerick, because now its channel traverses a 
ridge of Old Silurian rocks at Killaloe, which could not 
have existed as such when the river first commenced to 
run over a tract formed of Carboniferous beds since 
denuded. But it is amongst mountainous districts that 
the evidence of the former existence of old planes is most 
remarkable, because least expected. The higher ridges 
of the Grampians seen at a distance, or accurately drawn 
from a hypothetical standpoint (as on Mr. Knipes’ 
panoramic picture), forcibly bring home this idea to the 
mind. The ridges and peaks with very few exceptions 
tend to rise to an imaginary plane connecting the higher 
elevations, while several actual terraces coincide with the 
plane itself. Out of this old plane the existing valleys 
have been cut down, during the vast period of time 
descending from the pre-Devonian to the present. A 
still more ancient plane was that in which the Cambrian 
sandstones and conglomerates were strewn, formed of 
tough gneiss and hornblendic schists, with a gentle rise 
towards the east. The Scandinavian Promontory offers 
an illustration on a grand scale, and to these we might 
add the pre-Triassic plane formed of the denuded Devo- 
nian and Carboniferous rocks of Belgium and the Rhine 
highly tilted, convoluted, and contorted, through which 
the existing rivers have carved out their channels. But 
{ refrain from adding additional illustrations, as I must 
pass to the consideration of the question, How have such 
ancient planes been formed? Where was the agent 
capable of abrading down hundreds or thousands of feet 
of the most obdurate rocks over hundreds or thousands 
of square miles, and of transporting power sufficient 
to carry away the aééris of these vast ruins? The 
geologist answers, ‘Only give me an unlimited time, 
and the waves, tides, and currents of the seas act- 
ing along the coast-lines as they at present act, will 
effect all that you demand.’’ Granted that with “ un- 
limited” time all this may be effected, but this is a demand 
which the astronomers will not concede, and geologists 
must pay some respect to astronomers and mathematicians 
NATURE 
Le tet ee ee ee 
é Ws . ¥ — ‘ 
: 
(Dec. 22, 1881 
after all. But even with the aid of (practically) “un- 
limited’ time a serious objection meets us at the 
threshold. It is undeniable that the crust of the earth is 
always on the move, either upwards or downwards ; those 
who are not intensely uniformitarian in their views contend 
that this oscillatory motion of the crust was much more 
rapid in past geological times than at the present day. If 
this be admitted, and I hold that it is a necessary conse- 
quence of the constantly decreasing rapidity with which 
the secular cooling of the surface has progressed down- 
wards to the present day, how, let me ask, are you to get 
the coast to remain sufficiently long within range of such 
wave action as we see at present, to admit of the abrasion 
of the land to any considerable distance. The effects of 
wave action along our existing coasts, where formed of 
the more solid strata, is admittedly very slow, and in 
order to produce any great planing effects, the same 
coast-level (approximately) must be presented to it 
for a lengthened period; but with the required (practi- 
cally) ‘‘unlimited’’ time, the coast-level would be 
placed out of reach, either by elevation or submerg- 
ence. The hypothesis of approximately unlimited time 
seems to me, therefore, to be untenable. And what 
we require ts not time but force, in order to account for 
the planing away of vast masses of obdurate strata over 
extensive areas. Such additional force Prof. Ball has 
supplied us with. He has shown that at a comparatively 
early stage of geological history the tides may have had 
a denuding effect several hundred times more powerful 
than the present. With such a “stupendous tidal grind- 
ing-engine”” we may indeed conceive the work we have 
to account for accomplished, and the hypothesis of Prof. 
Ball approaches certainty, when it is considered that the 
character of the floors of the sea adjoining our coast- 
lines gives but slight evidence that such planes of marine 
denudation as I have attempted to describe, are in course 
of formation at the present day. They are phenomena 
of the past, not of the present, when wave and tidal 
action has, happily for mankind, subsided into restricted 
limits as compared with that of Palaeozoic and Mesozoic 
times. EDWARD HULL 
TELEGRAPHS IN CHINA 
N December 2 a telegram was received from Reuter’s 
agent at Shanghai, announcing that the telegraph 
line between that town and Tientsin was finished. In a 
few weeks we may expect to hear of the completion of 
the line to Peking. The capital of the Chinese empire, the 
chief seat of bigotry and hostility to foreign innovation, 
will then be in direct communication with Europe and 
America. There is, we believe, no doubt in the minds 
of those acquainted with the origin of this undertaking, 
that political motives alone dictated it. Hitherto, during 
the winter, when the mouth of the Peiho was closed by 
ice, couriers taking from twenty to thirty days on the 
journey travelled down the Grand Canal to the Yang- 
tsze conveying letters to Shanghai; or they were sent 
across Manchuria, in from fifteen to twenty days to 
Kiachta, where they reached the Great Northern Tele- 
graph Company's Siberian lines. These slow and un- 
certain modes of communication with the outer world 
were severely felt by the Chinese Government during the 
winters of 1879 and 1880, when its relations were almost 
broken off with Russia, when the land and sea forces of 
the latter were hanging like a thundercloud on the fron- 
tiers of China, and a peaceable solution of the Kuldja 
question seemed impossible. It was then brought home 
to the Peking authorities that their coasts might be in- 
vaded, their principal cities captured, and the foe be 
almost at their gates weeks before they heard the news. 
The bitter experience of these years taught the Chinese 
a hard lesson, but one which they speedily took to heart. 
Long before the Marquis Tséng brought the question to a 
