C seo ] 
XIX. A short Account of some Observations made with Chrono- 
meters, in tzvo Expeditions sent out by the Admiralty, at the 
recommendation of the Board of Longitude, for ascertaining 
the Longitude of Madeira and of Falmouth. In a Letter to 
Thomas Young, M. D. For. Sec. R. S . and Secretary to the 
Board of Longitude. By Dr. John Lewis Tiarks. 
Read April 29, 1824. 
Sir, 
A greeably to the wish of the Board of Longitude, com- 
municated to me through you, I beg to transmit to you the 
following short statement of the results of chronometrical 
observations, which were made by order of that Board in the 
year 1822 and 1823, chiefly regarding the longitude of places 
in England. I have compared the results thereby obtained, 
with the corresponding ones contained in the Account of the 
Trigonometrical Survey of England, published in several 
volumes of the Philosophical Transactions, and have added 
some remarks on the method employed in calculating the 
results of that Survey, with a view to explain the cause of 
the errors in the longitude of all stations, to which it seems to 
have given rise. In the year 1822, being ordered to determine 
the difference of longitude between the island of Madeira and 
Falmouth, I took fifteen chronometers from Greenwich to 
Falmouth by sea, and after having performed a voyage to 
Madeira, carried them back from Falmouth to Greenwich. 
Both before and after each of the two voyages between 
Greenwich and Falmouth, the time and the rates of the 
