24. National Geographic Magazme. 
his chronograph. By the use of the diagonal scale and the Rule 
of Three, he can without difficulty find the times of the signals 
received. The siphon recorders are well made, and the paper 
moves with great regularity. This system was used in the meas- 
urement between Galveston and Vera Cruz with great success. 
It was intended to employ the same method throughout the 
measurement on the west coast of America, but on arriving at 
Lima, it was found that the company owning the lines south of 
that point still used the mirror galvanometer, and it was of course - 
necessary to return to the old method. ‘The improved key was 
used however, which eliminated the error in sending signals. 
After this work was completed and the results published in 
1885, nothing was done in this line by the Bureau of Navigation 
for some years. Upon the return of the writer in the spring of 
1888, from a cruise in the South Pacific, he found that the subject 
of sending an expedition to complete the measurements in Mexico 
and Central America was under consideration in the Bureau of 
Navigation and the Hydrographic office. It was finally decided 
that the work should be done, and the writer was placed in charge. 
The instruments were brought out of their retirement, and by 
the aid of the Hydrographic Office a very complete outfit was 
furnished, and in November of last year a start was made from 
New York, the expedition proceeding by mail steamer to Vera 
Cruz. Here the spot occupied by Lieut. Com. Davis in ’83 was 
found, his transit pier, which was still standing was repaired, and 
instruments mounted. Lieut. Charles Laird, U. 8S. N., who had 
been identified with the longitude work since the China expedi- 
tion in 1881, was left in charge of the observatory at Vera Cruz, 
and the writer proceeded with his party to the small town of 
Coatzacoalcos, at the mouth of the river of the same name. ‘This. 
point is about one hundred and twenty miles southeast of Vera 
Cruz, and is the landing place of the cable. A land line extends 
from this point to Salina Cruz on the Pacific coast, a distance of 
about two hundred miles. In exchanging time signals between 
Vera Cruz and Coatzacoalcos, the automatic method was employed, 
the cable being short. The old wooden observatories were used 
at these points, but as they were too heavy for transportation 
across the Isthmus, tents made especially for astronomical pur- 
poses were substituted for them in the observations made on the 
Pacific coast. The journey across the Isthmus was slow, about 
two weeks being employed in traveling two hundred miles, though 
