Miscellaneous Intelligence. 319 



orbits should have a relation to the orbit of Jupiter. For, sup- 

 pose the orbits of the asteroids to be distributed in any manner 

 whatever, provided only that they shall make small angles with 

 the plane of Jupiter's orbit. The action of Jupiter should give 

 to each orbit a motion of its node, and these motions of the 

 nodes will not be the same for the different orbits. After the 

 lapse of a considerable time the orbits will thus evidently come 

 to be distributed somewhat symmetrically about Jupiter's orbit. 



This relation is moreover easily shown to be true in fact. For 

 if we take on the celestial sphere the poles of the 251 known 

 asteroid orbits and compute the center of gravity of these as 

 points of equal weight, that center of gravity is found to be only 

 3()'*0 from the pole of Jupitei''s orbit. 



Regarding this center of gravity as the pole of the mean-plane 

 of the asteroid orbits, we may say: that the plane of Jupiter's 

 orbit lies nearer to the mean-plane than does any single asteroid 

 orbit-plane to the mean-plane. The asteroids whose orbits have 

 inclinations to the mean-plane less than one degree are Medusa 

 and Euterpe, whose inclinations are 46' and 49'. 



Only one asteroid orbit-plane lies nearer to Jupiter's plane 

 than does the mean-plane to Jupiter's plane. The asteroids 

 whose orbits are inclined less than one degree to Jupiter's plane 

 are Euterpe, Elsa, and Yanadis, whose inclinations are 19', 43', 

 and 55'. h. a. n. 



5. Photographs of the Solar Spectrum. — The announcement 

 has been recently made that the photographic map of the normal 

 Solar Spectrum, made by Professor H. A. Rowland with one of 

 his concave gratings, is nearly complete. Seven plates on heavy 

 albumen paper are offered for sale ; each contains two strips of the 

 Spectrum, and one of them gives three ; they are three feet long 

 and one foot wide. The region covered by these plates extends 

 from wave length 3100 to 5790. Those interested are already 

 aware of the unique value of these photographs. "The price for 

 the set is $10, or $12 if mounted on cloth, and for a single plate 

 $2 and $2.25 respectively. Orders should be sent to the Pub- 

 lication Agency of the Johns Hopkins University, Baltimore, Md. 



Y. Miscellaneous Scientific Intelligence. 



1. Report of the International Polar Expedition to Point 

 P>arrow, Alaska. 695 pp. 8vo. Washington, 1885. — This vol- 

 ume contains an account of the results obtained by the United 

 States expedition to Point Barrow in 1881, 1882, and 1883. The 

 narrative of Lieutenant Ray is brief but interesting, and is fol- 

 lowed by a chapter by him giving an ethnographic sketch of the 

 natives ; both of these are accompanied by a number of excellent 

 full-paged phototypes, of the northern scenery, ice phenomena 

 and also portraits of the Eskimos. Part IV is devoted to the 

 mammals, birds, etc. This is written by John Murdoch except the 

 report on Mollusks, by W. H. Dall. The remainder of the volume 

 is devoted to the subject which formed the special study of the 



