ACROSS THE ISTHMUS OF PANAMA'. 
61 
a fall of only 16.13 feet, and thence to a small gravel bank named by us “Play a 
de los Injenieros,” distant altogether 1302 chains (16f miles) from Cruces, 
we found a fall from Gorgona of 21.82 feet, to a station precisely level with 
the high-water mark of spring tides in the Pacific, still being 34 miles from 
the mouth of the river. From this point we descended below the level of high- 
water-mark of the Pacific, until we arrived at a place called Palo Matias, 
distant from Cruces 2682 chains (33^ miles), and from the commencement of 
the levels in the river 4227 chains (52^ miles) : at this point we first observed 
the effects (slight as they were) of the tides of the North Sea, and the height of 
the water was 13.65 feet below the high-water mark at the Pacific ; this we 
therefore concluded to be the level of high-water mark in the Atlantic. We 
however continued our levellings 507 chains further, to a place called La Bruja, 
nearly 12 miles distant from the mouth of the Chagres, where the water in the 
dry season is very brackish, and from whence there is no perceptible current to 
the sea: here we found the level of the surface of the water, by several observa- 
tions at the time of high water in Chagres, to be 13.55 feet below the high-water 
mark in the Pacific, being 0.1 of a foot less than at Palo Matias, the difference 
being occasioned by our not having observed the tides at the former place so 
correctly as at the latter, as we determined to finish the observations at La 
Bruja. After 935 pairs of levellings, therefore, in a distance of nearly 82 miles, 
we found high-water mark in the Pacific to bel3.55 feet higher than high-water 
mark at La Bruja, which, from the circumstances above mentioned, is consi- 
dered to be the high-water level of the Atlantic at Chagres. 
The details of all the operations connected with the levellings are contained 
in a manuscript deposited in the library of the Royal Society ; they are further 
illustrated by a section of the whole on the scale of four inches to a mile. 
No proof levels were taken. I was aware, from the commencement, of the na- 
ture of the task I had entered upon, and knew too well that if I had the good 
fortune to be able to persevere a sufficient time to carry the levelling across the 
Isthmus, I should be but little capable of remaining during a third year, 
which such verification would have required. I therefore adopted such a 
scrupulous and rigid mode of proceeding as would render a verification 
unnecessary, and prevent the intrusion of even a trifling error ; an important 
one I am bold to say was nearly impossible. In the whole distance overland 
to the river Chagres, my companion being employed with the chain, I was 
