TIDAL OBSEE, VAT IONS. 



163 



These cotidal lines, which connect all places having high water at the same (Green- 

 wich) time, are laid down on the accompanying chart/ The tide wave consumes 

 very nearly eight hours in travelling from the southern cape of Greenland to Smith 

 Sound. 



Average Depth of Davis SiraU, Baffin Bay, and SmiiJi. Strait. — By means of the 

 preceding cotidal hours and the known distances of the localities in connection with 

 the theoretical deductions of Art. (1T4) "Tides and Waves," we find the average 

 depth of the sea along the channel-way as follows:— 



Davis Strait. Distance from Julianshaab to Whalefish Islands 680 statute miles 

 nearly ; difference in cotidal hour 3''.5, hence velocity in statute miles per hour 194, 

 and corresponding depth 2510 feet or 418 fathoms. 



' The general cotidal chart constructed by Mr. Whewell, more than thirty years ago (and repro- 

 duced in the astronomer royal's essay, " Tides and "Waves"), is very defective to the eastward'of 

 New Foundland, as will appear in attempting to join our cotidal lines with it ; it is due to the total 

 neglect of the powerful retarding influence of the banks of New Foundland. 



