PHILOSOPHICAL TRANSACTIONS 
I. On the Laws of the Rise and Fall of the Tide in the River Thames. 
By G. 13. Airy, Esq., M.A., F.R.S., Astronomer Royal. 
Received July 3, — Read November 25, 1841. 
In the winter of 1840-1841, an extensive series of observations of tides was made, in 
accordance with my suggestions, at Deptford Royal Victualling Yard. For these ob- 
servations, as well as for those which follow (and which form more immediately the 
subject of this paper), I am indebted to Captain Shirreff, R.N., Captain Superin- 
tendent of the Royal Victualling Yard and Dock Yard at Deptford. By the kind- 
ness of this able officer, I was allowed to give such directions to the police constables 
on duty in the Victualling Yard as I thought necessary for my purpose; and by his 
continual superintendence of the observations, I was able to satisfy myself that they 
were conducted exactly as I desired, and were worthy of the fullest confidence. I 
cannot adequately express my sense of the attention which thus put me in possession 
of the data that I desired, and in the very form in which I desired them, without the 
smallest trouble to me in the whole transaction. 
The mode of making the observations was the following. Under the direction of 
Captain Shirreff, a vertical scale of feet and inches was marked on the return of the 
wharf-wall adjoining to' the principal landing-stairs of the Victualling Yard. The 
graduations increased in going downwards, the top of the wharf-wall being the zero. 
As the bottom of this return of the wall was sometimes dry at low water, a level line 
was carried to the extremity of the causeway at the bottom of the principal stairs, 
and another vertical scale (in continuation of the former) was measured there. Thus 
every observation of the surface of the water was a measure of its depression below 
the top of the wharf-wall. The times of the observations were in all cases the 
quarters of hours of mean solar time, as indicated by the striking of the clock of the 
Victualling Yard. It is proper to mention, that, in consequence of the extensive 
visibility of the signal-ball of the Royal Observatory (which is dropped at l h p.m. 
precisely), the public clocks in the neighbourhood of Greenwich are for the most part 
extremely well regulated; and I have therefore little doubt that the times of obser- 
vation are pretty accurately those which they profess to be. 
The object of the first series of observations was simply to ascertain the times of 
MDCCCXLII. 
B 
