438 
NATURE 
[DECEMBER II, 1913 
Jubaland to the Lorian Swamp, and Dr. C. A. Hill 
the exploration of the limestone caverns of Gaping 
Ghyll, in Yorkshire. 
Friday morning was devoted to local geography. 
After Miss C, A. Simpson’s paper, which dealt in 
detail with the physical and human circumstances of 
ihe Rugby district, Prof. W. W. Watts analysed in 
masterly fashion the geography of Shropshire. Con- 
trasting the lowlands north and east of the Severn 
with the uplands of the south and west, he exhibited 
graphically the influence on rivers, roads, and place- 
names of the forested Edges and the wooded barrier 
of the Severn Gorge. The more immediate’ neigh- 
bourhood of Birmingham furnished material for three 
papers. Mr. P. E. Martineau showed how thé Mid- 
land Plateau, an upland area of 1000 square miles, 
sharply limited to the south by a steep escarpment, 
had marked the meeting of the English invaders from 
the Humber with the Saxons from Wessex. Mr. 
W. H. Foxall traced the growth of the city from a 
market at the convergence of trackways; and Mr. H. 
Kay contrasted the Black Country, which owed to 
its varied minerals a population of 1,750,000, a density 
exceeded on an equal area only in London, with the 
historical scenery of its borderland. 
On Monday, before Dr. Bruce’s paper on Spits- 
bergen, Mr. C. B. Fawcett contributed an anthropo- 
geographic study of fiord lands in relation with the 
physical conditions of Norway, the north-west coast 
of North America, and Magellanes. In each region a 
narrow strip of coast was backed by barren highlands; 
each had a damp climate unfavourable to agriculture, 
with an ice-free sea; in each, expansion took place 
along the waterways. Social development depended 
on skill in navigation, local and limited among the 
Magellanes, confined to dug-out canoes among the 
Amerinds, but highly developed where the Norsemen 
were in touch with the shipbuilding nations of Europe. 
Mr. A. G. Ogilvie investigated the origin and growth 
of two remarkable promontories which screen the 
Inverness Firth from the Moray Firth, partly through 
geological changes, partly through tidal and wind 
currents. Prof. J. W. Gregory gave a lantern lecture 
on Australia, in preparation for the coming visit of 
the Association to that continent. 
On Tuesday morning the section divided into two 
parts, one joining with members of Section A to 
receive papers on geodesy, the other discussing natural 
regions of the world, the topic being introduced by 
Prof. A. J. Herbertson. In the latter the most in- 
teresting points arose in connection with the place of 
man in the region. Some speakers held that human 
interests formed the only satisfactory principle of 
division; others that the title ‘‘ natural” excluded man 
from consideration; and others that man and his 
environment were so mutually interactive as to be 
indivisible in such relations. 
At the joint meeting with Section A, Capt. H. S. L. 
Winterbotham, R.E., read a paper on the accuracy 
of the principal triangulation of the United Kingdom. 
He said that the work having been carried out in the 
years 1783 to 1853, the precision of the angular 
measurements was less than that of most of the 
continental worl, which is of later date. The probable 
error of an observed angle as calculated from the 
triangular errors is 123", as against 0°54” for the 
mean of all national systems up to 1892. These facts 
had led to the expression of doubts whether the 
British work was sufficiently accurate for incorpora- 
tion with the more modern European work. This 
question was discussed at the British Association 
meetings in 1906 and 1908, and in the latter year a 
letter was written on behalf of the Council of the 
ture and Fisheries, suggesting the remeasurement 
of a small portion of the triangulation remote from 
the old bases. This has now been done, and there 
are available as checks six bases in the British Isles 
(including three measured before |1820 with steel 
chains), and also a connection across the Channel to — 
the new French meridional arc. The greatest dis-— 
crepancy found was 1/42000 between the new base 
= 
at Lossiemouth and the new Paris base. 
The accuracy of a triangulation depends not only 
on the precision of the angular measurements, but “9 
In this latter 
respect the British triangulation has a considerable 
In order to get — 
a rough idea of how far this had compensated for — 
” 
also on the ‘‘strength”’ of the figure. 
advantage over most other work. 
the inferior angular measurements a comparison was 
made with seventy-seven pairs of bases in all parts of 
the world. On the assumption that the error 
generated varied as the square root of the distance 
from the base it was found that the mean discrepancy 
for too miles of triangulation was o’0000044 in the 
logarithm, or 1/g9000. Taking the six pairs of bases 
available for the British Isles, the mean discrepancy 
was 00000029 in the logarithm, or 1/152000. It 
would appear, therefore, that the principal triangula- 
tion is sufficiently accurate for incorporation with 
the more modern work on the continent, and that if 
funds became available for remeasuring the British 
ares, they would be better employed for other geodetic 
work. 
Capt. H. G. Lyons, F.R.S., read a short paper on 
the terms used in triangulation, directing attention to 
the great and confusing differences in the terms 
adopted. He recommended that the terms first order, 
second order, third order, and fourth order should 
be adopted, the order depending on the average tri- 
angular error. The discussion showed that the feeling 
of the meeting was very much in favour of the pro- 
posal, and the question was brought up at the meeting 
of the general committee, and finally referred to the 
council, with a view to the whole question being 
brought to the notice of those concerned. M. Ch. 
Lallemand, in the discussion, stated that the subject 
was being considered by the International Geodetic 
Association. 
A paper by Mr. E. B. H. Wade, read by Mr. Keeling, 
gave particulars of some longitude observations in 
Egypt along a line Helwan—Dagsur to investigate the 
local attraction in that district. There is a difference 
in the local attraction between the places named of 
about 8". ae 
Mr. B. F. E. Keeling read a paper on the precision 
of field latitudes in Egypt. The latitudes were observed 
with a 10-inch Repsold theodolite. The probable error 
of a single night’s observations worked out at about 
oi", but the agreement between observations on 
different nights was not as good as this would indi- 
cate. To investigate this, a series of monthly observa- 
tions for latitude were carried out in the grounds of 
the Helwan observatory, using a procedure identical 
with that followed in the field. The results were 
much less accordant than was to be expected from 
the individual probable errors. A comparison of the 
different monthly sets of observations (11 in all) gave 
a probable error for one set of 05”, and this would 
appear to be the correct probable error to assign to 
the field latitudes of the Egyptian Geodetic Survey. 
It was pointed out in the discussion that as these 
discrepancies were not found at permanent observa- 
tories, they must either be due to some peculiarity in 
Egypt, or more probably to the methods and instru- 
ments employed. Among those who took part in the 
discussions were M. Ch. Lallemand, Col. C. F. Close, 
Association to the President of the Board of Agricul- | and Prof. H. H. Turner. 
NO. 2302, VOL. 92] 
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“Ss, 
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