NOVEMBER 8, 1906 | 
THE INTERNATIONAL 
CONFERENCE AT BUDA PEST. 
HE International Geodetic Association held its 
triennial conference at Buda Pest from September 
20 to 28, and | had the honour of serving as the dele- 
gate of our Government. By the kindness of the 
Hungarian Academy the meetings were held in their 
handsome building, and the arrangements for our 
reception, which had been made by M. Louis 
de Bodola, were in every way admirable. Before 
considering the scientific work of the conference 
I may mention that the Prime Minister, Dr. 
Wekerle, invited the members of the ‘‘ Permanent 
- Commission ’’ to dinner, and that the Archduke 
Joseph afterwards received all the delegates at the 
palace. On subsequent days the Burgomeister of 
Buda Pest gave a dinner in our honour, as also did 
Count Albert Apponyi, Minister of Public Instruction. 
The work of the conference was more interesting 
than that of any other at which I have been present, 
and the time was barely sufficient for the adequate 
discussion of many subjects of importance. In an 
article of this character it will clearly be impossible 
to do more than indicate in general terms the subjects 
which were considered. 
The systematic observation of the variation of lati- 
tude, which is the special province of Dr. Albrecht, 
was naturally the subject of much discussion. The 
existence of a mysterious term in the expression for 
the position of the pole was discovered some years ago 
by Prof. Kimura. If this term, which is denoted by 
the letter 2, has a real physical existence, it would 
indicate that the equator oscillates backwards and for- 
wards, moving parallel to itself. It appeared that 
observations conducted in the southern hemisphere 
would quickly determine the reality of the supposed 
motion. Accordingly, at the conference of Copen- 
hagen in 1903 it was resolved that observations in the 
southern hemisphere should be instituted, and should 
be carried out for a period of at least two years. The 
southern observations of latitude are to be made at 
Bayswater, West Australia, where Dr. Hessen began 
his observations on June 6, 1906, and at Oncativo, in 
the Argentine Republic, where Prof. Carnera began 
work on May 5. These two stations are in S. latitude 
31° 55’. We also heard from Mr. Innes that latitude 
observations will probably be commenced at Johannes- 
burg (S. latitude 26° 12’) by the end of the present 
year. With regard to the observations in the 
northern hemisphere, it was resolved that they should 
be continued, at least until the year 1909, when the 
next conference will meet. The northern stations are 
Pulkova and Leyden, and in N. latitude 39° 8! 
Mizusawa, Charjui, Carloforte, Gaithersburg, Cin- 
cinnati,t and Ukiah, together with Tolyo in latitude 
35° 39’. Prof. Helmert gave an interesting account 
of the present condition of the whole investigation, 
and he directed attention to certain oscillations or 
systematic errors of which the physical meaning is 
as yet altogether obscure. Whatever their meaning 
may be, their magnitudes are excessively minute. 
Another report of importance was one by Dr. 
Albrecht on the use of wireless telegraphy for the 
determination of differences of longitude. He con- 
cludes that this method may be relied upon to give as 
good results as those derived from telegraphy through 
wires. 
Dr. Hecker had undertaken, at the expense of the 
association, a second long sea voyage for the purpose 
of determining the value of gravity at sea. His first 
voyage was from Portugal to Brazil, and the 
GEODETIC 
* The observations at Cincinnati will, as I understand, be discontinued 
shortly. : 
NO. 1932, VOL. 75 | 
NATURE 33 
second was in the Indian Ocean and across the 
Pacific. He presented a short preliminary report, in 
which he stated that the intensity of gravity for the 
deeper part of the Pacific Ocean is approximately 
normal, and agrees closely with Helmert’s formula 
of the year 1901. His experience in the first voyage 
had enabled him to effect considerable improvements 
in the procedure. The method depends upon the 
determination of the temperature of boiling water 
and the simultaneous observation of the height of the 
barometer. The difficulties in attaining at sea to the 
requisite degree of accuracy are so numerous that it 
is matter of surprise that trustworthy results can be 
obtained. There seems, however, to be now no doubt 
that we may trust his conclusions. Dr. Hecker ex- 
hibited his apparatus with five barometers furnished 
with the means for obtaining continuous photographic 
records of the height. One of the greatest difficulties 
to be contended with is the motion of the ship, for 
the pitching and rolling make the mercury in the 
barometer ‘‘pump,’’ and the photographic trace of 
the barometer height is marked with regular notches. 
Dr. Hecker is to be congratulated on the skill with 
which he has overcome this and many other difficul- 
ties. His conclusions form one of the most note- 
worthy acquisitions to geodetic knowledge of the last 
twenty years. 
MM. Claude and Driencourt gave an account of 
the use of their prismatic astrolabe. It gave me the 
impression that it might be an instrument of much 
use to geodesists. ) 
The measurement of base lines naturally afforded 
an important subject of discussion, and M. Guillaume, 
assistant director of the International Bureau of 
Weights and Measures at Bréteuil, gave an admirable 
account of the recent improvements which have been 
effected in the use of the Jaderin wires. It would 
appear that the measurement of base lines has now 
reached such perfection that we cannot look for any 
great advance in geodetic accuracy in this direction. 
Errors due to triangulation accumulate rapidly, and 
the modern practice is fo measure short bases about 
every 200 miles. The Simplon Tunnel has been used 
by the Swiss geodesists as a base line, and was 
measured by the Jiderin apparatus. The railway 
company was good enough to surrender the tunnel 
to the geodesists for five clear days, and by means 
of continuous work day and night they were able to 
complete their task. A special form of tripod for 
supporting the wires was devised; it rolled along 
the railway lines, and in this way the labour of trans- 
porting the tripods was considerably diminished. 
The national reports furnished by the several dele- 
@ates were in many cases of great interest, but I can 
only refer to a few of them. 
The work of the Swiss in the measurement of a 
base along the Simplon Tunnel has already been 
mentioned. é 
A proposal has been made for the collaboration of 
the French and Italians whereby the island of 
Sardinia may be linked to Corsica and to the Italian 
mainland. 
The French delegates gave a final account of the 
measurement of the great arc of Peru. This work 
took five years, and eleven officers of the Service 
Géographique de l’Armée and_ twenty-eight under- 
officers and soldiers took part in it. Several of the 
staff died of exposure and hard work in the Cordillera, 
and the conference received this intimation standing, 
in token of respect to their French comrades who lost 
their lives in the cause of science. 
I myself presented reports from Colonel Burrard, 
R.E., on the work in India, and from Sir David 
| Gill, Colonel Morris, and Mr. Simms, on the geo- 
