SCIENCE. 



35 



who is acquainted with the range of variation of structure 

 in these groups possesses the key to every peculiarity 

 which is met with in the primates, the carnivora, and the 

 ungulata. Given the common plan of the insectivora 

 and of the rodentia, and granting that the modifications 

 of the structure of the limbs, of the brain, and of the ali- 

 mentary and reproductive viscera which occur among 

 them may exist and accumulate elsewhere, and the de- 

 rivation of all eutheria from animals which, except for 

 their diffuse placentation, would be insectivores, is a sim- 

 ple deduction from the law of evolution. I venture to ex- 

 press a confident expectation that investigation into the 

 mammalia fauna of the mesozoic epoch will, sooner or 

 later, fill up these blanks. 



RECENT DISCOVERIES RELATING TO THE 

 DOUBLE STARS OF THE DORPAT CATA- 

 LOGUE. 



By S. W. Burnham. 



The distinguished Russian astronomer, Struve, pub- 

 lished in 1837 the results of a thorough examination of 

 the heavens for the discovery of double stars between the 

 north pole and 15 south declination. This great cata- 

 logue, MensurcE Micrometrica, included all the double 

 stars within these limits known prior to the observations 

 of Struve, mainly due to the researches of Sir William 

 Herschel, and at the time of its publication presented all 

 that was known on this subject of astronomy. The 

 whole number of double stars catalogued and measured 

 by Struve was about 3000. The superiority of the tele- 

 scope used at Dorpat for this class of work, over the 

 much larger reflectors employed by the Herschels, is re- 

 peatedly shown by the observations. Many of the Her- 

 schel pairs, observed with apertures from eighteen inches 

 to four feet, were found by Struve with the 9.6-inch re- 

 fractor to be really triple, one of the components being a 

 close pair. When Sturve's great work was published, it 

 seemed as though there was lutle left for subsequent ob- 

 servers to do except in the way of re -observing the Struve 

 stars. So complete and systematic had been his scrutiny 

 of the northern heavens, it was considered that new dis- 

 coveries among the stars found by Struve to be single 

 would necessarily be of rare occurrence, and particularly 

 after the publication, in 1850, of the Pulkowa Catalogue of 

 500 stars, which comprised omitted stars and later discov- 

 eries, principally by Otto Struve, the successor of his father 

 as Director of the new Imperial Observatory. This last 

 mentioned catalogue was much more interesting, with re- 

 spect to the class of stars it contained, than the other. 

 The Pulkowa 1 5-inch refractor was in every respect 

 superior to the Dorpat glass, as well as larger. Substan- 

 tially all the wide and comparativelv easy pairs had been 

 collected in Mensurce Micromeh 'icce, so that later dis- 

 coveries were necessarily either very close pairs, or the 

 components were very unequal, and, therefore, this cata- 

 logue furnishes a much larger proportion of binary and 

 other interesting systems. In the twenty-five years fol- 

 lowing this epoch, the whole number of double star dis- 

 coveries by all observers would not exceed fifty ; but 

 many important series of measures of the Struve stars 

 were made by English, German and Italian astronomers, 

 and this work was steadily continued at Pulkowa, result- 

 ing in showing the periods and motions of many of the 

 more rapid binary systems, and the relations of other 

 double stars. 



That these catalogues were really very incomplete, 

 with reference to the number of double stars actually ex- 

 isting, is apparent from the fact that the writer in the 

 last ten years has discovered at least 900 new pairs, and 

 more than halt of them with a telescope greatly inferior 

 in size to the smallest of the instruments used by the 

 Russian astronomers. That there was left much that 

 was new to discover in the Struve stars will appear from 



the number which have been again divided by later ob- 

 servers. In some instances, doubtless, the close pair was 

 missed by Struve because it was single or much closer at 

 that time, but certainly in the great majority of instances 

 this is improbable, and the true explanation will probably 

 be found in the improved defining power of the later re- 

 fracting telescopes. For double star work more than any 

 other, perfect definition is of the first importance. Some- 

 thing may be done in observing the moon, plane' s, 

 nebulae, etc., with a large instrument of poor definition, 

 but for the discovery or measurement of close and difficult 

 double stars it is practically useless. It should be men- 

 tioned as a fact that every star in the following table was 

 discovered with a refracting telescope. 



The follow ng list comprises all the stars of the Dorpat 

 Catalogue where a closer component has been discovered 

 since the observations of Struve. More than half of these 



IN U . 



v 



_ 



oiar. 



Struv 's 

 Pair. 



New 

 Corn- 

 par ion 



Discoverer. 



I. . 



17 





27". 06 



2". 04 



Burnham 



2. . 



26 





13 .29 



O .60 



O. Struve 



3- ■ 



39 





19 .90 



.40 



Dembovvski 



4- • 



157 





12 .40 



O .85 



Burnham 



5- • 



171 



y AndromcdiE. 



29 .69 



3 -69 



Burnham * 



6. . 



205 



1° -33 



.50 



O. Struve 



7- • 



258 





70 .30 



1 .20 



Burnham 



8. . 



3i8 



20 Persei 



14 .04 



-34 



Burnham 



9. . 



366 





48 .97 



1 .99 



Bu rnham 



10. . 



439 





23 -70 



.40 



Burnham 



ir . . 



610 



7 Camelopardi 



25 -64 



1 .24 



Dembovvski 



12. . 



668 



ji Orionis 



9 - T 4 



0.2? 



Burnham 



13- • 



692 



Ononis S2 . . . . 



34 -86 



.48 



Burnham 



14. ■ 



707 





27 -77 



1 .11 



Burnham 



15 . . 



721 





24 -32 



.46 



Burnham 



16. . 



808 





16 .06 



2 .60 



Dembovvski 



17. . 



888 



Canis Maj. 136 



2 .83 



.27 



Burnham 



18. . 



1019 



37 -84 



6 .12 



Dembovvski 



19. . 



1026 



Canis Maj. 139 



17 -85 



.48 



Burnham 



20. . 



1057 





15 .87 



.69 



Burnham 



21 . . 



1097 





29 -34 



5 -93 



Dembovvski 



22. . 



11 79 





ig .75 



3 -76 



Burnham 



23. . 



1481 





20 .20 



.So 



Burnham 



24. . 



1516 





7 -9° 



7 .61 



O. Struve 



25 . . 



1780 



86 Virginis(AC) 



26 .94 



1 .61 



(ab) Burnham 





1812 







1 .72 



(CD) Burnham 



26. . 



Libra? 213 .... 



14 .02 



.47 



O. Struve 



27. . 



2005 



28 .54 



1 .47 



(ab) Burnham 



28. . 



2214 





19 .49 



1 -43 



Dembovvski 



29. . 



2220 



31 .09 



.96 



Alvan Clark 



30. . 



2287 





22 .33 



1 .71 



Burnham 



3i- • 



2306 





12 .81 



-95 



Dembovvski 



32. • 



2342 





28 .80 



8 .86 



Burnham 



33- • 



2435 



(AC) 



10 .73 



1 -43 



(ab) Burnham 







Cygni 4 





2 .90 



(CD) Howe 



34- • 



2479 



6 .72 



-57 



Dembovvski 



35- ■ 



2481 





4 -03 



.40 iSecchi 



36.. 



2535 





26 .31 



1 .22 Dembovvski 



37- • 



2538 





52 .81 



4 -37 



Burnham 



38.. 



2539 





5 .60 



4.78 



Burnham 



39- • 



2549 





22 .86 



1 -93 



Burnham 



40. . 



2570 





4 .16 



.29 



A. G. Clark 



41.. 



2589 



8-77 



.25 



A. G. Clark 



42. . 



2607 



Cyemi 116. .. . 



3 -23 



-3 



0. Struve 



43- • 



2630 



(AD) 



11 .30 



6 .47 



[AB) Burnham 











7 -75 



ac) Burnham 



44. . 



2657 





11 .71 



.60 



O. Struve 



45- • 



2690 



/i Delphini. . . . 



14 .88 



.50 



Dawes 



46.. 



2704 



35 06 



.20 



Burnham 



47 - • 



2777 



6 Equulei .... 



37 -98 



.35 O. Struve 



48.. 



2793 





26 .51 



.56 



Burnham 



49. . 



2815 





7 -50 



.90 Dembovvski 



50. . 



2824 



k Pegasi 



11 .76 



.27 Burnham 



5i- • 



2959 





13 -77 



8.31 



Bu rnham 



52. . 



2966 





30 .72 



.41 



0. Struve 



53- • 



3130 





2 .86 



.3? IO. Struve 



