IV ROYAL SOCIETY OF CANADA 
now issued by the Tidal Survey, three series of comparisons were re- 
quired :—(1). With tide tables as above referred to, published by local 
almanacs. (2). With the tides as computed for our ports from the data 
given by the United States Coast Survey. (3). A direct comparison of 
the tide tables issued by this Survey, with the tides as actually observed. 
The results of the first two comparisons are given in condensed 
form in the Report of Progress, and the large amount of improvement 
in accuracy is there shown in the form of percentage values. In the 
Tide Tables of the United States Coast Survey, the tides of the St. 
Lawrence estuary and the Gulf of St. Lawrence are referred to Ports of 
Reference in all parts of the world ; the selection being made solely on 
the basis of a range in the tide which is nearly the same. The type of 
the tide is thus ignored ; and the result is often very wide of the mark, 
especially where the tide presents some special feature such as diurnal 
inequality. The error in time may then amount to an hour and a half, 
early or late. The methods now used by the Tidal Survey are distinctly 
superior, as shown by the comparisons made; as they are based upon a 
careful consideration of the local conditions derived from observation. 
The direct comparisons of the tide tables of this Survey with the 
tide as observed at Halifax, St. John, N.B., and Quebec, are given in 
tabular form appended to the Report now issued ; accompanied by a 
discussion of the result. 
TIDES ON THE LOWER ST. LAWRENCE REFERRED TO QUEBEC. 
The desirability of obtaining the best tidal data possible in this 
region need not be enlarged upon, not only because of the importance of 
the tides themselves to navigation, but also to obtain an adequate basis 
for the examination of the strong tidal currents on a route traversed by 
so large a volume of commerce. A thorough examination was made of 
the difference in the time of the tide based upon the simultaneous records 
obtained from the three principal stations at South-west Point of Anti- 
costi, Father Point and Quebec, at the extreme ends and the middle of 
the estuary, a distance of 450 miles. 
The time of the tide at South-west Point and Father Point can now 
be deduced from the Quebec tide tables by means of constant differences, 
which have been derived from a long series of simultaneous observations, 
as explained in previous reports. The tide tables for Father Point are 
computed from the Quebec tables in this way, one difference.being used 
for high water and another for low water. With regard to the accuracy 
of the result as thus obtained, the point of importance is to know how 
far the differences in time for individual tides will vary from the average 
