354 PROCEEDINGS OF THE AMERICAN ACADEMY 



will not be slow to give liim a higher. Long after the death of an 

 artist, the scales in which his merits are weighed continue to rise and 

 fall as partial or imi^artial hands add or remove the weights, at last 

 they settle, and a final judgment is made. This we may safely leave 

 to posterity, convinced that in the long run every man is estimated as 

 he deserves. 



Professor P. A. Hansen has been taken away from geometrical 

 astronomy, and terminated the labors of a distinctly marked, original, 

 and well-rounded life, at a ripe old age. He was born in the Duchy 

 of Schleswig, at Fondem, near the close of the year 1795, and was 

 appointed director of the ducal observatory at Gotha in 1825. His 

 principal contribution to science, to which his other theoretical investi- 

 gations were mostly accessory, was a new method of computing the 

 perturbations of a planet, which he regarded as especially applicable 

 to the moon and the asteroids. His development of the perturbative 

 function was partly numerical and partly analytic, and his memoirs 

 concerning it are original and suggestive. There are other peculiari- 

 ties of his method which deserve careful study. He does not compute 

 directly the perturbations of the polar co-ordinates as in Laplace's 

 method, nor those of the elements of the orbits with Lagrange's; but, 

 for the planet's longitude, he finds a perturbed time, with which argu- 

 ment the fixed tables are entered. He also enters the tables of the 

 radius vector with the same argument, and completes the calculation 

 with additional tables for the radius vector and the latitude. Hansen 

 ap})lied his method to the theory of Saturn disturbed by Jupiter, to the 

 Moon, and to some of the asteroids. His tables of the Moon were 

 published in a handsome form by the English government, were liber- 

 ally distributed to astronomers of other nations, and have been em- 

 ployed in the construction of the British Nautical Almanac. They are 

 esjjecially arranged for the calculations of an ephemeris, and the form 

 of final interpolation is much to be commended. The resistance of the 

 lunar motions to complete submission to known laws is strikingly ex- 

 emplified in the deviations which are already detected in her path from 

 these last and presumably best tables. But the final result will cer- 

 tainly be a more enlarged knowledge of the constitution of the solar 

 system and of the laws of its changes. 



Jacques Adolphe Lambert Quetelet was born at Ghent on 

 the 22d of February, 1796, and died at Brussels, February 17, 1874. 

 His taste for the sciences for which he was afterwards distinguished 



