306 E. D. Preston — Deflection of the 



In view of the importance of the determination of these 

 deflections in the survey of the islands, as well as the general 

 scientific interest in the subject, the Hawaiian government 

 was led to ask the cooperation of th# United States in the 

 work of determining with precision a number of astronomical 

 latitudes. Accordingly, in December, 1886, with the sanction 

 of the Honorable Secretary of the Treasury, the Superintend- 

 ent of the Coast and Geodetic Survey loaned the necessary in- 

 struments, and granted one of the members of the service a 

 leave of absence long enough to make the observations On 

 the part of the Hawaiian Survey, Messrs. F. S. Dodge and W. 

 A. Wall assisted in the gravity observations. Mr. Wall was 

 permanently attached to the party and recorded all the latitude 

 work. 



The credit of the work, therefore, belongs in part to both 

 governments. The Island Survey bore all the expenses, and 

 selected the stations ; the Coast and Geodetic Survey loaned 

 the instruments, furnished the observer, and is making the 

 computations. 



Later it was thought desirable to supplement the latitude 

 work, by the determination of the force of gravity on the top 

 of one of the mountains, and at the sea-level. This would 

 give a check on the deflections determined at the foot of the 

 mountain, by means of the zenith telescope. For, whether 

 there exist great caverns under the visible surface or not, the 

 pendulum will give us a value for the mean density of the whole 

 mass. Then, knowing the volume and density, it is a simple 

 arithmetical process to find its influence on the plumb-line sus- 

 pended at a given distance from it. The liberality of the 

 Hawaiian government can only be commended when we find it 

 devoting time and money to the solution of scientific questions 

 in which the rest of the world is quite as much interested. 



The scope of the work was as follows : Fourteen latitude 

 stations were to be established on the four principal islands of 

 the group, viz : Kauai, Oahu, Maui and Hawaii. These were 

 distributed in such a manner as to bring out the deflections of 

 the plumb-line ; being in general north and south of the high 

 mountains. At each one of these stations it was proposed to 

 observe thirty-three pairs of stars on three successive nights ; 

 which would bring the probable error of the resulting latitude 

 below one-tenth of a second of arc. 



Practically, however, this plan could not be rigidly adhered 

 to. At all the windward stations the weather was very un- 

 favorable for astronomical observations. At Kohala the wind 

 was always too strong to allow us to pitch a tent in which to 

 live. An old sugar storehouse, long since abandoned, served 

 instead. At Hilo, where the rain-fall is sixteen feet in one 



