Page:The American Cyclopædia (1879) Volume VI.djvu/192

 184 DOGWOOD exceeding more than twofold that of Canopus, the second star in brilliancy, and more than fourfold that of Alpha Centauri, the third, whose light the same astronomer takes as the standard for first magnitude stars. But the variable Eta Argus, shining now as a sixth magnitude star, nearly equalled Sirius in lustre 30 years ago. Sirius was known to the an- cients as a red star, Ptolemy describing it as vTroKipfa, reddish yellow, and Seneca speaking of it as ruddier even than Mars. Its light at present is perfectly white. Examined with the spectroscope by Kutherfurd and Huggins, it shows a spectrum crossed by a multitude of fine lines, and by four very strong lines. The four lines are identified with the hydrogen lines. Their strength and breadth seem to imply that the star is surrounded by an ex- tensive atmosphere of hydrogen, existing close to the photosphere, at a very great pressure. From a measurement of the position of the F line of hydrogen, which appears slightly dis- placed toward the red end of the spectrum, Huggins has inferred that the star is receding from us at the rate of about 29 miles a second, or, taking into account the sun's own motion, at the rate of 26 miles a second in space. Late- ly, however, he has seen reason to believe that this estimate of the velocity is too high. The annual parallax of Sirius has been estimated at 0*150" by Henderson and Maclear, and at 0-250" by Cleveland Abbe". If we assume 0-2" as the value, the distance of the star ex- ceeds about a million times the distance of the sun. From the observed apparent motion of the star upon the celestial sphere, it follows, assuming this estimate, that it is travelling athwart the direction of the line of sight at the rate of about 15 miles a second. Com- bining this motion with Huggins's estimate of the motion of recession, it follows that it is actually moving through space at the rate of 33 miles a second. Certain peculiarities of the proper motion of Sirius have led astronomers to the belief that the star has a companion, not equally bright, but large enough to give Sirius an appreciable motion tf circulation around their common centre of gravity. DOGWOOD (cornus, Linn.), small deciduous trees or shrubs of the order cornacece, natives of Europe, Asia, and North America, of which there are several species. C. alternifolia (Linn.), the alternate-leaved dogwood, is indigenous to North America, and is found in shady woods or by river banks in every latitude. It fre- quently attains a height of 15 to 20 ft. The leaves are alternate, ovate, and acute ; flowers wliiti-, May to July; fruit dark blue, ripening in October. Of all* the species of cornus, the flowering dogwood (C. florida, Linn.) is the most beautiful, and in its native soil under favorable circumstances attains a height of 30 to 35 ft. The specific name florida was bestowed because of the profusion of its flow- ers. Specific characters: branches shining; leaves ovate, acuminate, pale beneath ; flowers umbellate, protruded after the leaves; ^v 00 of involucre large, roundish, retuse, white and very showy ; drupes ovate and bright red. It is found as far northward as New Hamp- Alternate-leaved Dogwood (Cornus alternifolia). shire, but particularly abounds in New Jersey, Pennsylvania, Maryland, and Virginia, where the soil is moist; in Florida and the Carolinas it is found only in swamps ; in Ohio, Kentucky, and Tennessee, it is not found in the forests except where the soil is gravelly. It was first described in Ray's Historia Plantarum (1686- 1704), and afterward by Catesby in his " Natural History of Carolina." The wood is hard, fine- grained, and susceptible of a high polish. It Flowering Dogwood (Cornus florida). enters into the construction of many articles of ornament and utility, such as the handles of mallets, toys, harrow teeth, hames for horse collars, and the shoeing of sleds. The inner