6 SEVENTH REPORT—1837. 
period over which the observations extend, it was found to amount to 
2 hours 48 minutes, being 33 minutes greater than the time of high 
water at full and change, as given for Dundee in the Nautical Al- 
manac. The “vulgar establishment” of that port is therefore 2 
hours 48 minutes. As at London, Bristol, Liverpool, and other 
places where good observations have been made, so at Dundee, the 
interval of time between the meridian passage of the moon and the 
occurrence of high water is greatest about new and full moon, and 
decreases till about the seventh and eighth days after these periods. 
This inequality in the intervals alluded to has been appropriately 
termed, by Mr. Whewell, the “semi-menstrual, or half-monthly in- 
equality ;’ and if we draw a line, and erect upon it fifteen equidistant 
ordinates or perpendiculars, to represent, by their comparative lengths, 
the fifteen different intervals which occur between the time of high 
water and the moon’s northing and southing, from full to change, the 
line joining the extremities of the ordinates generally forms a pretty 
regular curve. According to Mr. Lubbock and Mr. Whewell, if we 
perform such an operation with the intervals between the time of high 
water and the moon’s meridian passage at London, from full to change, 
we obtain the curve represented by the boldest line in the following 
diagram. 
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