10 REPORT OF THE SECRETARY. 



N. Stockwell. If but one planet revolved around the sun its path in space 

 would be a true ellipse, which would always be the same in form and 

 position ; but if several planets revolve at the same time around the 

 central body, their mutual attraction will disturb the regularity of the 

 elliptical motion. The mutual action of the planets on each other pro- 

 duces two classes of disturbance, one of which consists in a change of the 

 motion of each planet in its elliptical orbit, in some parts of its path 

 moving faster and in others slower than it would if undisturbed ; the 

 other consists of a change in the form and relative position of the 

 elliptical orbit. The first is called the periodic inequalities, and the 

 second the secular variations. They are, however, both periodical, 

 though the first runs through its changes in a short time, while the lat- 

 ter requires centuries to complete its cycle. The object of the investi- 

 gations of Mr. Stockwell is to determine the numerical value of the 

 secular changes of the elements of the orbits of the planets of our sys- 

 tem. Several partial solutions of this problem have been obtained by 

 previous authors, but they have been approximations based upon data 

 less perfect than that which is at present afforded in the discovery of 

 the new planet Neptune, and the better determination of the masses of 

 the other bodies composing our system. 



The expense of the publication of this paper is defrayed by the lib- 

 eral donatiou of $1,200 from a friend of science, who declines to allow 

 his name to be mentioned. We cannot, however, permit the fact to pass 

 unnoticed of this example of the high appreciation of the value of 

 abstract science since it does honor to the intelligence and liberality of one 

 of our citizens engaged in active business life, and may serve as an 

 example to stimulate other donations of a similar character. 



In several of the previous reports mention has been made of a gram- 

 mar and dictionary of the Choctaw language, in process of preparation 

 for the Institution by Dr. Byington, for many years a missionary among 

 the Choctaw Indians. This work was finally submitted to the Institu- 

 tion for publication, but having been found on examination to require 

 corrections it was returned to the author in order that these might be 

 made. Before, however, this work was completed, Dr. Byington died, 

 and his MS. was given for revision to Dr. Brinton, of Philadelphia. 

 It was again submitted to the Institution and referred to a commission 

 for critical examination. Dr. Brinton, however, nbt satisfied with the 

 report of this commission, withdrew the memoir, and presented it to the 

 American Philosophical Society, in whose transactions it has since been 

 printed. No objection was made on the part of the Institution to this 

 transfer, since it has been from the first a part of its policy never to 

 expend any portion of its funds in doing that which can be done by 

 other means. 



It will be remembered that in 1867, at the suggestion and expense of 

 the Institution, a geological exploration of a portion of the Louisiana 

 coast was made by Professor E. W. Hilgard, of the University of Mis- 



