76 



SCIENCE 



[N. S. Vol. XXXIII. No. 837 



properly adjusted in the camera. The wires are 

 then held firmly on the satellite, as in the case of 

 the polar cap of Mars. 



The conditions of seeing necessary for success 

 in this class of work were almost entirely absent 

 during the opposition of Mars. There was only 

 one night, 1909, September 28, on which the con- 

 ditions were favorable, and this for a short time 

 only. The best results are therefore meager, but 

 the promise of success is good when conditions 

 will permit the best work. 



The photographs of September 28 show the 

 region of the Syrtis Major. They contain essen- 

 tially all the details that could be seen with the 

 same telescope visually. 



6. Dr. MacMillan shows that if two of the 

 masses are finite and equal and revolve about 

 their common center of gravity in circles, and if 

 the third mass is infinitesimal and is projected in 

 the axis of revolution of the two finite bodies then 

 the motion of the infinitesimal body can be deter- 

 mined by means of elliptic functions. If the 

 velocity of projection is not too great the motion 

 of the infinitesimal is periodic and it is shown 

 how to construct periodic series representing the 

 motion. 



7. Twenty- two photographs were made with the 

 lOi-inch telescope of the University of Minnesota 

 between the years 1897-1910. Ten plates were 

 measured and reduced to standard of October 19, 

 1909. The faintest stars measured were about 

 fourteenth magnitude. No variability in bright- 

 ness was detected. The proper motions are all 

 less than 0".l ± 0".01 per year. The measures 

 have not yet been discussed for parallax. 



8. From a study of 3,300 solar prominences, by 

 Dr. Sloeum, photographed in the light of the 

 H-line of calcium with the Rumford spectrohelio- 

 graph of the Yerkes Observatory during the past 

 seven years, 1,100 were found which by their 

 shapes or movements indicate a horizontal cir- 

 culation. The tendency is poleward between lati- 

 tudes 20° and 55°, equatorward beyond 55°, and 

 neutral near the equator. The contrast of tend- 

 ency is greater in the northern hemisphere than 

 in the southern in the ratio of 2 to 1. The 

 average height above the chromosphere of the 

 prominences studied is 0'.7 or 30,000 km. The 

 earlier plates do not afford data for determining 

 velocities. From the later plates low prominences 

 of the cloud type give appiirent velocities from 1 

 to 10 km. per second. One detached cloud at a 

 height of 7' or 300,000 km. shows a horizontal 

 velocity of 50 km. per second, while eruptive 



prominences have been observed the north and 

 south horizontal component of whose velocity 

 reaches 200 km. per second. 



9. The paper by Mr. Parkhurat deals with the 



relative advantages of two proposed systems of 

 standard magnitude stars; those in the neighbor- 

 hood of the pole, and the white stars in the par- 

 ticular region photographed. It compares the 

 possible errors arising from differences of trans- 

 parency of the sky wnen a distant region is 

 referred to the polar standards with the errors 

 due to the magnitudes of stars found in the visual 

 catalogues of the region photographed, and the 

 uncertainties due to the allowance made for spec- 

 tral type of these standards. 



10. In accordance with experimental demon- 

 strations devised by Dr. Siebel, the ellipticity of 

 the earth may be considered as the result in part 

 of the withdrawal of a greater amount of kinetic 

 energy in one of the three directions (in which 

 the molecular motions of a liquid subjected only 

 to its own internal forces may be resolved) dur- 

 ing its congelation or solidification. For the 

 experimental demonstration of this phenomenon 

 a drop of water is suspended in a mixture of 

 Beechwood Creosote and ether, which is cooled 

 sufficiently to make the drop of water congeal 

 almost at once. The moment when this takes 

 place, the perfect globular shape of the drop 

 changes into an ellipsoidal form, whereby the 

 vertical diameter of the same is reduced at least 

 one fourth; the now solid and fiattened drop, on 

 account of the lower density acquired, rises slowly 

 to the surface. 



11. A particular kind of dials useful in certain 

 calculations were discussed in the paper by Dr. 

 Wetherill. 



12. The present investigation is based on meas- 

 ures of seventeen plates made wiiJ. the Crossby 

 reflector of the Lick Observatory. It proves im- 

 possible to separate the parallax from atmos- 

 pheric dispersion without further observational 

 material which the Lick Observatory will provide. 

 In addition to masking the effect of parallax the 

 atmospheric dispersion produces shifts of the 

 position of the central star amounting to 0".2. 



Photographs made with a reflector are prob- 

 ably more subject to the effects of atmospheric 

 dispersion than those made with a refractor. 



Certain hitherto unexplained discordances in 

 visual observations of the central star may be due 

 to dispersion. 



13. True photographs of the nebula were taken 

 with the slitless spectroscope of the Crossby 



