MADE ON THE COASTS OF EUROPE AND AMERICA IN JUNE 1835. 291 
already stated with respect to those of June 1834, that they reflect great credit both 
upon the intelligence and the punctuality of the officers and men of the coast-guard 
service. 
4. Having had my views seconded by the favour and exertions of so many persons 
of various ranks and countries, it became me to turn to the best advantage the large 
mass of materials thus collected. It will, however, be seen on consideration, that the 
arrangement and reduction of this collection was beyond the powers of an individual. 
The effective places of observation being about five hundred, there were one thousand 
tides observed every day for twenty days ; and as, for each tide, even taking high water 
only, the time and height were to be considered, I had forty thousand numbers to 
deal with as the basis of any calculations by which I might deduce general results 
from this large experiment. 
I found in this, as in other similar instances, the Admiralty ready to assist me. 
Captain Beaufort kindly allowed Mr. Dessiou, of the Hydrographer’s Office, to per- 
form my calculations, as far as the business of the office left him time ; but this being 
quite insufficient for my purpose, Lord Auckland, at that time First Lord of the 
Admiralty, did me the favour of complying with my suggestion that two additional 
clerks should be engaged, who might carry on these calculations ; and Earl Minto, 
on his accession to the same office, readily agreed to retain these calculators in the 
same employment till it should be completed. These gentlemen, Mr. D. Ross and 
Mr. H. Boddy, have, under Mr. Dessiou’s superintendence, performed the calcula- 
tions, by which I have been enabled to draw from the tide observations of June the 
inferences which are the subject of this paper. 
5. One of my principal objects was to fix with precision the form of the cotidal 
lines, by which the motion of the tide-wave is exhibited, and to which I had already 
attempted to make an approximation*. For this purpose the times of high water 
were treated as follows. 
At each place the differences between the time of high water and the time of a 
preceding transit of the moon (which differences I call the Lunitidal Intervals) were 
taken for the whole series of observations. Next, these lunitidal intervals were laid 
down as the ordinates of a curve, the time of the moon’s transit after the sun’s being 
the abscissa. In this manner I had, for each place, a curve, which represented (in the 
way so frequently referred to by Mr. Lubbock and myself) the semimenstrual in- 
equality of the lunitidal intervals, affected by the various errors and peculiarities of 
the observations. The inspection of these curves afforded me the means of judging 
of the best mode of combining them so as to get rid of local and casual anomalies. 
From these curves also the mean lunitidal interval, or corrected establishment of each 
place, was readily obtained. For this purpose a curve was drawn by the eye which 
should pass among the points representing the observations, and should retain, as 
much as possible, the general form of the semimenstrual curve. The intervals being 
* Philosophical Transactions, 1833, Part I. 
2 P 2 
