July 1, 1891.] 



KNOWLEDGE 



129 



In the fore-limb, of which the skeleton is represented 

 in Fi}'. 4, the bones of both the arm and fore-arm are 



Birds as the lords of the air is in accordance with what we 

 have observed elsewhere, namely, the replacement, with the 

 advance of time, of a lower by a higher type of organiza- 

 tion. The Bats, indeed, which belong to the highest class 

 of animals, appear to have been the latest in which the 

 power of tiight has been developed ; but since most of 

 them are of comparatively small size, and of more or less 

 completely crepuscular and nocturnal habits, they have 

 never entered seriously into competition with the Bii'ds, 

 so that both groups are found existing side by side in full 

 development. 



Fij^. 3. — The bones of the right fore-liml» of a Bat, seen from 

 above. A., bono of arm; /■.'/.. bones of fore-arm; //./■..thumb; y>//., 

 claw of thumb; m.c, metacarpus; /j/i", L'lul. ord, 4th, and oth 

 fingers. 



relatively slender and considerably more elongated than 

 usual. The thumb remams comparatively small, and ends 

 in a claw ; but all the other fingers — more especially 

 the third or middle one — are enormously elongated, so 

 that the third, fourth, and fifth, which have no claws at the 

 end, are absolutely longer than either the fore-arm or 

 the arm. Between these elongated spider-like fingers the 

 wing-membrane is stretched, the whole structure per- 

 mitting of the wing being folded, when at rest, in the 

 manner familiar to all. A comparison of Fig. 3 with 

 Fig. 2, or, still better, with the figure of the skeleton of a 

 Pterodactyle, given in the article on Flying Dragons, will 

 .show how essentially the wing of a Bat difi'ers from that 

 of a Pterodactyle. As we have said, the single finger sup- 

 porting the wing-membrane of a Pterodactyle corresponds 

 either with the one marked i or tliat marked rt in Fig. 4 

 (probably the latter), and it may therefore be said that 

 while a Pterodactyle files with one finger, a Bat fiies with 

 its whole hand. Equally marked is the ditt'erence between 

 the wing of a Bat and that uf a Bird ; the latter having 

 only the first three fingers of the Bat's wing developed, 

 and all of these being strangely modified from the ordinary 

 form, while the chief elongation has taken place in the 

 bones of the arm and fore-arm, instead of in those of the 

 fingers, and Hight is efiected by the aid of feathers instead 

 of by a membrane. 



This completes our survey of the various modes of Hight 

 obtaining in the aiiiuiiil kingdom. In it we have indicated 

 the dilVercnce between spurious and true flight, have shown 

 how the former is but an extreme development of the long 

 leaps taken by arboreal animals, and liave suggested how 

 it may have gradually passed onwards into true Hight. AVe 

 have also seen liow the wings of the Invertebrate animals 

 differ in tuto from those of tlu' \'ertehrates ; while among 

 the Vertebrates true Hight luis been independently deve- 

 loped in three distinct groups — Pterodactyles, Birds, and 

 Bats — on totally ditt'erent structural lines; the latter 

 instance thus allbrding us an excellent example of the way 

 in which difi'erent groups of animals may be variously 

 modified to occupy the same position in the realm of 

 nature. The supersession of the Pterodactyles by the 



THE COMPANION TO « URSvE MAJORIS 

 (/8 1077). 



By S. W. BURNHAM. 



THE close companion to a Ursiie Majoris, which was 

 found with the 30-incb refractor in the early part 

 of 1889, has now been measured each year since 

 that time. These observations show clearly that 

 the companion is moving round the principal star 

 in a retrograde direction, and that the two form a physical 

 system. The proper motion of a is not large (0'144" in 

 the direction of 240-.5°), but it is sufBcient to show in the 

 measures of so close a pair, even in the two years covered 

 by the observations. 



The following are the measures down to this time : — 



18H9-19 32G-1° 0-91" ^3 4n. 



lK90-2(i 320-1° 0-87" ft 4n. 



1891-3() 31()-H° 0-80" ft 4n. 



It is not unlikely that it may prove to be a rapid binary, 



and that the distance is now about maximum. In that 



case a more rapid change in the angle may be looked for 



soon. It is easily measured with the large telescope when 



the conditions are good, but with a distance of one-third, 



or even one-half that given in the measures, it would 



probably be a severe test for the SG-inch. So far as I 



know it has not been seen anywhere else, though some of 



the large refractors ought to show it. I hope to measure 



it regularly each year for some time to come. 



Lick Observatorv, Jiotc 2,n<l. 



ASTRONOMY AS TAUGHT BY ACADEMY 

 PICTURES. 



T<i the Kditor of Knowledge. 



Sir, — Will you allow me to say a few words in reply to 

 your notice of my picture of Jeremiah Horrocks in the 

 Koyal Academy. Three points are there singled out for 

 animadversion. First you say that I have drawn Venus 

 too small, " the black disc representing Venus should be 

 larger." You do not say how much, so the reader might 

 infer some terrible disproportion in my delineation. May 

 I point out that the major diameter of the Sun's disc in 

 the composition measures one inch and three-quarters, 

 and the minor one about half that size. The sub-division 

 of the former into 30 will give the proportional size of 

 ^'enus, this being a speck not much, if at all, larger in 

 size than that which I have delineated, keeping in mind 

 the fact that this is a foresliortened perspective view, and 

 not one seen full front, as it would be in a circular diagram. 

 You add that the place of Venus upon tlie Sim's disc is not 

 quite low enough on the right hand limb. As a fact I 

 have copied it from the sketch to be found in the text of 

 the " Venus in solo visa,'' left by Ilorrocks and published 

 by Hevelius. 



