LXXVIII ROYAL SOCIETY OF CANADA 



form a general basis for the details required locally. With this view, 

 the coast may be divided into three regions, (1) the Strait of Georgia, 

 (2) the northern coast to Port Simpson, (3) the outer coast of Van- 

 couver Island. In this scheme, the Strait of Fuca must be considered 

 as an additional region, already commanded by Victoria for which tide 

 tables are published. 



To command these various regions, there are three tide gauges 

 which have been in operation in the past; and six new tidal stations 

 have been erected last season wliich need not be described in detail. 



The strong tidal currents which are found in so many of the passes 

 and inlets are evidently occasioned by the rise and fall of the tide ; but 

 it should not be over-looked that their strength is chiefly due to thi 

 diflîerence of the time rf high or low water in the two directions. It is 

 thus clear that tlie tide is the basis of the current ; and also that correc: 

 time for the observations is an essential of the first importance. This 

 is one of the chief difficulties on the coast; and it has been found 

 necessary to use chronometers, or to erect special instruments by which 

 the time can be obtained directly from the sun. 



To summarize the results aimed at, it may be said in brief that the 

 time of tlie tide is the basis of all knowledge of currents and slack 

 water; while the height of the tide is chiefly of importance in harbours 

 for the construction of wharfs, dredging, the outfall of sewers and all 

 such questions. 



The main object of this survey, as a branch of the Marine Depart- 

 ment, is to deal with the time of the tide; since this is the matter of chief 

 importance to navigation; and the question of levels, even though they 

 are indispensable for the purposes above mentioned, must remain 

 secondar3^ In the strong tidal currents of British Columbia, it is in- 

 formation as to the time of slack water that is most wanted by the 

 mariner. But the value of reliable levels, which can only be obtained 

 from tidal observations, makes it seem right to take the addition,?! 

 trouble necessary to secure them. The opportunity of this season, has 

 enabled the results with regard to datum planes and bench-marks to bf 

 published in a complete form, up to the stage now reached. 



There is good hope now that a sound basis is laid for the tidal in- 

 formation required in the province, for the tide itself, the currents, and 

 the levels which result from a continuous tidal record. No doubt there 

 will be need in future for much detail work where channels and passages 

 are so numerous and that there are so many local variations, but on the 

 general plan adopted the apparent complications should disappear when 

 the results are systematically worked out. 



