6 National Geographic Magazme. 
The U. 8. Steamer Fortune was designated by the Navy 
Department for the conveyance of the expedition, and Lieut. 
Commander (now Commander), F. M. Green, U. 8. N. was placed 
in charge. This officer had given great attention to the subject, 
was a practiced observer, and exceptionally well qualified for the 
position. The services of Mr. Miles Rock, a skillful astronomer 
and computer who is now chief of the boundary survey of 
Guatemala, were obtained as principal astronomical assistant. 
The breaking out in the autumn of 1873, of the trouble with 
Spain and Cuba, over the Virginius affair, delayed the expedition 
until the next year, but in November 1874, a start was made from 
Washington, and after a short stay m Kingston, Jamacia, 
Aspinwall was reached early in December. Mr. Rock with one set 
of instruments proceeded immediately to Panama, while Lieut. 
Commander Green remained in Aspinwall with the other. The 
outfit for each party consisted of :—first, a portable observatory. 
This was made of wood in sections, framework of ash, covered 
with tongued and grooved pine boards. The sections were con- 
nected when set up by iron knees and bolts. When packed it 
was not difficult to transport, and it could be put up, or taken 
down in an hour. When set up it was about eight feet square, 
with doors in all sides, and a shed roof. The roof was made in 
three sections, the middle one being hinged so that it could be 
raised for observing. ‘These observatories proved to be very 
strong and serviceable. They remained in use for a number of 
years with occasional slight repairs, were transported many thou- 
sand miles and set up in a great number of places in Kurope, Asia, 
North and South America. They were designed by Mr. J. A. 
Rogers, and constructed at the Washington Navy Yard. Upon 
arriving at a point where observations were to be made, after 
obtaining the necessary permits from the local authorities, a suit- 
able location for the observatory was the first consideration. The 
essential requirements were, a clear view of the heavens in the 
meridian, firm ground, a spot secluded enough not to attract 
attention from inquisitive idlers, and proximity to the telegraph 
office, or end of the telegraph line. Such a spot being found and 
permission being obtaimed from the owner for its use, an approxi- 
mate meridian line was laid out by compass, and the house set up 
with reference to it. Experience soon showed the advisability of 
making certain additions to the observatory not contemplated by 
the designer, but which added much to convenience and comfort. 
