2 
: 
SECTIONAL TRANSACTIONS.—E. 407 
extensive magnetic survey has been carried out in new and difficult territory 
at absolutely no expense by combining it with the land survey.—The instruments 
used, the reasons for their adoption, their accuracy in the field, and the method 
of standardisation and observing.—The method used in correcting observations 
for diurnal inequality and in reducing to epoch in compiling isomagnetic maps.— 
A general summary of this work accomplished to date: observations, secular 
change and diurnal inequality observations, and maps and publications. 
9. Mr. N. Oaitviz.—The Work of the Geodetic Survey of Canada. 
The most important functions of the Geodetic Survey are to establish, in a 
permanent manner, a series of points of reference, at convenient distances apart, 
whose geographical position have been accurately determined by nets of triangu- 
lation and astronomical observations. It also determines the accurate elevations 
above sea-level of permanently marked points along main railways and in the 
principal towns and cities, by lines of precise levelling. It therefore forms the 
basis and provides the foundation which, without it, would have to be duplicated 
in some manner by each separate organisation carrying on surveys, Federal 
Departments, Provinciai Governments, Municipalities, &c. This centralisation 
prevents duplication and expense, and assures efficiency and economy. Federal 
and Provincial Departments and Municipalities realise these points, and, 
wherever possible, are turning over this feature of their operations to the 
Geodetic Survey, which can perform it most satisfactorily and economically. 
When connected together by the Geodetic Survey data, older surveys can be 
‘made of good use and the expense of map-making is very materially reduced, 
the decrease in expense being larger as time goes on. With new surveys 
errors can be discovered and localised, and the surveys can be accurately con- 
nected to other Canadian surveys, past and future. 
10. Dr. W. Brxt Dawson (Superintendent of Tidal Surveys of 
Canada).—The Survey of Tides and Currents in Canadian 
Waters: Progress and Methods, 1893 to 1924. 
A concise outline is given of the general procedure in carrying on a survey 
of tides and currents in waters where there was little or no information to begin 
upon. On the two coasts of Canada the tides are extremely varied, and exemplify 
almost every tidal feature. Some indication is given regarding methods and 
appliances employed, in the hope of being helpful to parts of the British Empire 
where less progress has been made. The work of the Survey includes: (1) In- 
vestigations of currents and tidal streams, and information on the temperature 
and salinity of the waters; (2) tidal observations as a basis for tide-tables, in- 
cluding methods of analysis and calculation ; (3) tide-levels, and determination 
of mean sea-level. 
Friday, August 8. 
11. Dr. Vaucuan CornisH.—Wind, Wave, and Swell on the North 
Atlantic Ocean. 
During a voyage from Southampton to Trinidad and back by R.M.S. Oruba 
the author took the period of the waves several times daily, from which their 
speed was calculated. The speed of the wind was ascertained by means of a 
Robinson anemometer lent by the Meteorological Office. 
The speed of the wind ranged from 13.9 to 23.6 statute miles per hour. That 
of the waves was in all cases less, the difference ranging from 1.0 mile an hour 
to a little more than 8.0 miles an hour. When swell and wave ran precisely 
in the same direction, and on one day when no swell was recorded, the speed 
of the wave was so nearly equal to that of the wind that the breeze blowing 
over the ridges was only equal to the ‘light air’ which barely suffices to give 
steerage way to a fishing smack, and would be detected on land by drift of 
smoke but would not move a wind-vane. 
When the swell followed but crossed the wave the difference in speed of 
wind and wave was greater, and the difference increased rapidly when the cross- 
ing swelling swell was meeting, instead of following, the wave. When the waves 
