TRANSACTIONS OF SECTION E. 555 
TABLE 2.7 
Table showing the discrepancy between bases, assuming that this discrepancy 
varies as the square root of the distance, and reducing the length of 100 miles 
in each case. 
Discrepancy 
National No. of in the 7th eee 
Surveys of Comparisons Place of RUSH Dae, 
Logarithms 
Europe ... 36 52 Report of the International Geo- 
detic Association, 1893, p. 540 
et seq., omitting 5 bad connec- 
tions in Russia (since re- 
1 
tesiaatl measured) 
2 
SOT ane 8 Account of the Operations of the 
Great Trig]. Survey of India, 
[ 1 ] Vols. 2, 6 and 12 
197000 
2 
South Africa . 13 47 Reports of the Geodetic Survey of 
South Africa, Vols. 4 and 5, in- 
cluding two cases of a junction 
[ ] ] from a base to a side of pre- 
92000 viously adjusted Triangulation 
United States of 20 36 Report of the United States Coast 
America : and Geodetic Survey for 1900 
and 1904. Professional papers 
[ 1 | of the Corps of Engineers, U.S. 
121000 
Army, No. 24 
Mean ; : 1 
Total Ele te es ad 44 Corresponding to 99000 
® “ : 1 
ted Kingd 6 28: C foye ss 
Uni ingdom 85 orresponding 152000 
The very close agreement between the Salisbury Plain and Paris bases 
is responsible for the high place taken in this table by the Principal Triangula- 
tion. If we neglect this connection the remaining five give the figure 131000 - 00° 
This table shows that the linear errors of the Principal Triangulation of 
the United Kingdom are in the same terms as those to be expected in Modern 
Triangulation carried out in chains over similar distances, and that, if the 700 
miles of meridivnal arc between the Straits of Dover and Saxavord in the 
Shetland Islands were remeasured, it is not likely that the new measurement 
would differ from the old by more than 25 yards. 
(ii) The Precise Definition of Terms used in Higher Surveying. 
By Captain H. G. Lyons, F.B.S. 
(iii) Longitude Work in Egypt. By E. B. H. Wave. 
In the last two years several longitudes have been measured in Egypt by 
exchange of telegraphic signals with Helwan Observatory. Mr. Knox Shaw 
determined local time at Helwan, using the Brunner transit instrument, and 
Mr. Wade employed the method of equal altitudes in the field. All star 
observations and telegraphic signals were chronographically registered, and 
1 Table 2 makes no claim to be exhaustive. 
