432 THE POPULAR SCIENCE MO NT JILT. 



grai)licd to the receiving station and repeated to insure correctness. 

 The time of arrival of these signals was recorded by the chronograph 

 at the receiving stations, and five similar sets were exchanged in each 

 direction, making sixty-five comparisons each way. 



After five nights of this work, zenith telescope observations of 

 pairs of stars were made on four nights for latitude. 



In this way, during the wintei-, the stations of Panama, Aspinwall, 

 Kingston, Santiago de Cuba, and Havana, were occupied, the exact 

 difference of time between each station and the next and the latitude 

 of each being ascertained. It was intended to continue the work to 

 Key West, thus connecting with a Coast Survey station, but the occur- 

 rence of yellow fever among the crew of the Fortune, and the break- 

 ing out of that disease at Key West, caused the postponement of this 

 measurement till the next season. 



By combining these ascertained differences of time, and applying 

 the result to a determined position, the longitude of each place will 

 be decided with a very small limit of error. 



In addition to the above observations, the exact habitual error of 

 observing, or relative personal equation of the two observers, must be 

 ascertained and applied to the result.^ 



The method of star-signals, or the comparison of the times at whicli 

 the same star passes over the meridians of two stations, is seldom used 

 now, and therefore is not described in detail. 



The authorities of each country visited extended the most grati- 

 fying courtesy and assistance to the officers of the expedition. Es- 

 pecially was this the case in the island of Cuba, where a Spanish naval 

 officer was detailed to assist in the work. 



On the 5th of April last, all work practicable during this season 

 being finished, the Fortune left Havana, completing her cruise by ar- 

 riving at the Washington Navy- Yard on the 12th of the same month. 



The computation of the numerous observations made during the 

 past winter is now being prepared, and, as soon as completed, the re- 

 sults will be published. 



Some imjjrovements and modifications, wljich the experience of the 

 past year has suggested, will be made in the instruments and outfit, 

 and the same officers in a larger and more commodious vessel will 

 leave the United States during the coming autumn, to continue the 

 measurements through the Virgin and Windward Islands to the coast 

 of South America. j 



Although the naval surveyors of nearly all maritime nations (par- 

 ticularly the English) are constantly at work perfecting the knowl- 

 edge of the earth's surface, it is believed that this is the first systematic 

 naval expedition for establishing by this method secondary meridians 

 to which other positions may be referred. 



In connection with their preparations for observing the recent 

 ^ See Popular Science Monthly, vol. vi., p. 385. 



