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SCIENCE 



[N. S. Vol. XXX. No. 777 



The PJiotographic Doublet of the Dominion Ob- 

 servatory: R. M. Motherwell. 

 The images produced by the Brashear 8-inch 

 doublet were surrounded by a halo and a series 

 of teffts by the Hartmann method showed this to 

 be due to spherical aberration. On the lens being 

 refigured, by the kindness of the Brashear Com- 

 pany, the halo disappeared and it now gives small 

 and sharply defined images with a widely ex- 

 tended field. Diagrams were shown of the aber- 

 ration at the normal separation of the front 

 elements, at increased separations, as well as 

 after refiguring. 



On the Photographs of Comet c 1908 (More- 

 house) : E. E. Barnabd. 



About 350 photographs of this comet were ob- 

 tained with the three lenses of the Bruce tele- 

 scope of the Yerkes Observatory. These pictures 

 cover essentially all the more remarkable phe- 

 nomena of the comet during its visibility in these 

 latitudes, including the extraordinary outbursts 

 or changes that occurred on September 30 and 

 October 15, 1908. The last photograph was ob- 

 tained here on December 13, 1908, when the comet 

 was close to the horizon. The photograph of 

 December 11 was one of the most remarkable of 

 the entire set. The paper also deals briefly with 

 the possible cause of these extraordinary changes 

 in the tail of the comet. 



On Some Experiments in Photographing Enlarged 

 Images of the Planets, direct loith the Forty- 

 inch Telescope: E. E. Barnard. 

 Experiments have recently been made, with 

 improved facilities, in photographing directly en- 

 larged images of the planets with the 40-ineh 

 telescope. Some of the photographs of Jupiter 

 which show the belts well, stand a subsequent 

 enlargement of upwards of two or three inches. 

 Better results are hoped for by the use of a new 

 screen by Mr. Wallace. The results so far show 

 that it is now mainly a matter of favorable defini- 

 tion to secure valuable photographs. 

 On the Proper Motion of some of the Small Stars 

 in the Dense Cluster M 92 HereuUs: E. E. 

 Barnard. 



The visual and photographic measures of the 

 great star clusters show that but little motion 

 exists in any of the small stars composing them. 

 In M 92 Herculis motion is shown in several of 

 the smaller stars, amounting in two cases to as 

 much as 5" a century. These two stars are of 

 magnitude 13.3 and 14. Motion also seems cer- 

 tain in at least three other stars of between mag- 

 nitude 14 and 15. The next fifty years ought to 



give us some idea of the relative motion of many 

 of the stars in this cluster. These motions have 

 been brought to light, in this cluster, perhaps 

 because a closer investigation has been made for 

 that purpose than in the case of other clusters. 

 Lack of Spectroscopic Evidence of a Dispersion 

 of Light in Space: Edwin B. Frost. 

 Examination of plates of spectroscopic binaries, 

 taken with the Bruce spectrograph of the Yerkes 

 Observatory, does not give evidence of a difference 

 of radial velocity for different wave-lengths. The 

 star j3 Cephei, having a period of 4" 34", would 

 appear especially suitable in this connection. A 

 large range ot wave-lengths is obtained for this 

 star only on one-prism plates, and on these any 

 such effect would probably be masked by the acci- 

 dental errors of measurement. Statistics were 

 read for the star /* Orionis, which has a short 

 period, 0.77 day. The spectrum has sharp lines, 

 and many plates have been obtained with three 

 prisms. These show no systematic difference of 

 velocity at different wave-lengths. Mention was 

 made of work successfully commenced with one 

 prism in the red end of the spectrum. While 

 intended for a different purpose, these plates 

 would be available also for a wider range of wave- 

 length in ,this connection. 



Vertical Temperature Gradients in the Atmos- 

 phere as Determined hy Season and by Types of 

 Weather: W. J. Humphreys. 

 A large number of sounding-balloon records 

 were grouped according to season and height of 

 the barometer. The results show that while the 

 difference between summer and winter tempera- 

 tures is most pronounced at the surface of the 

 earth, it is still decided — about half as great — 

 at the higaest elevations thus far reached, and 

 that this difference remains essentially constant 

 above an elevation of about ten kilometers, or in 

 the isothermal region. The seasonal effect there- 

 fore extends presumably through the entire at- 

 mosphere. On grouping into separate curves the 

 summer gradients obtained during high and low 

 barometric conditions, respectively, it is seen that 

 the high barometer, or clear weather conditions, 

 insure higher temperatures than does the low 

 barometer at the surface of the earth and up to 

 near the isothermal region where the conditions 

 are just the reverse; that is, colder in clear than 

 in cloudy weather. Barometer changes have the 

 same effect on the temperature gradients both 

 winter and summer, except at the surface of the 

 earth. Here the temperature is the lowest in 

 winter during clear weather, or high barometer. 



