Mr. J. Nixon on the Tides in the Bay of Morecambe. 267 



afterwards descended to the same (height or) division, will 

 give, alike from observations of every division, the time of 

 high water; but as the rate will generally vary, not only from 

 astronomical causes, but also from sudden changes in the force 

 or direction of the wind, it follows that the series of times ob- 

 tained from the several divisions will neither coincide with 

 each other, nor with the true instant, the error increasing 

 (irregularly) from the highest to the lowest division noted. In 

 the course of observations, frequently protracted to three hours, 

 as the extreme difference between the times obtained never 

 exceeded five minutes, the one derived from the highest divi- 

 sion rarely required a correction of moment to reduce it to 

 the true instant of high water. 



The watch made use of, which has a detached lever, but 

 is without compensation-curb, &c, keeps a tolerably uniform 

 rate when not exposed, as was sometimes the case, to violent 

 shocks on travelling. Its error was ascertained from time to 

 time at a station near Hest-bank from sets of observations made 

 in the afternoon, of the instants the sun's upper and lower limbs 

 had descended to a certain altitude (measured by a box sex- 

 tant,) above the sea at the horizon, or later in the afternoon 

 above its margin (?) about Peel Castle, a distance of 15-f- 

 miles. The dip of the sea, found by the sector to vary, ac- 

 cording to the state of the tide and refraction, from 8' r/ to 

 11' 2S", was taken at 10' 0". On one occasion the sun's 

 height was obtained in the morning by reflection from the 

 tranquil surface of the canal. (See Table I.) From the 

 highest* part of the north-east battlement of the canal bridge 

 on the Oversands road from Hest-bank, go two and a half 

 feet towards the opposite side of the bridge, and the station, 

 51 feet distant, (the east end of the roadside wall,) will be in 

 a line with the breakwater pole. The height of the wall top 

 above the long level of the Lancaster canal (extending from 

 Preston nearly to Burton-in-Kendal,) measured 13 feet. The 

 (trigonometrical) latitude was found to be 54° 5' 34" north, 

 and the longitude 2° 48' 5" (or 11 min. 12 sec. in time) west 

 of Greenwich. The distance from Hest-bank wall to the 

 Breakwater pole, 2339*3 feetf, was calculated from the angles 

 taken by the four-inch theodolite at both ends of a base line 

 extending 855 feet (as measured by a corrected tape) along 

 the west margin of the Oversands road near the bathing- 



* In 1829, the fall to the canal was 17 feet 3 inches, and 17 feet in 

 1832, the fall to the wall top being 4 feet 1 inch. 



t Differing little from, but preferable to, the length obtained by a trian- 

 gulation connected with that of Colonel Mudge. 



2 M 2 



