On Seeing at a tHstance. 65 



tinct Tision, or of seeing in gi^neral. The latter has a much 

 larger semidiameter than the former ; and the series for the one 

 is in animals different from that of the other. The extent of 

 distinct vision, as is shewn by Treviranus, is pretty nearly in re- 

 lation with the distance of the lens from the retina in the axis 

 of the eye. But the power of seeing at a distance, Treviranus 

 remarks, depends, in general, in land animals, on the absolute 

 magnitude of the semidiameter of the external surface of the 

 cornea. The larger this is, the greater is the number of rays 

 that reach from distant objects through the cornea to the inte- 

 rior of the eye, and the more easily are such objects rendered 

 visible. But this applies to land animals only. The cornea has 

 no such value in aquatic animals, in arresting the rays of light, as 

 that the limits of vision can be determined by it. If we arrange 

 land animals and birds according to the measure of their power 

 of seeing in the distance, we obtain the following series : — 



Horse (Equus Caballus) ... 73 Night-Heron (Ardea Nycticorax) 27 



Ox (Bos Taurus) 6G Short-eared Owl (Strix brachyo- 



Asiatic Elephant (Elephas asiat.) 65 tos) 27 



Antilope Rupicapra .... 64 Psittacus Aracanga 25 



Lynx (Felis Lynx) .... 55 Turkey (Meleagris Gallopavo) 25 



Kangaroo (Didelphis gigantea) . 60 Tame Swan (Anas Cygnus) . . 23 



Wolf (Can is Lupus) .... 45 Ardea stellaris ....*. 22 



Fox (Canis Vulpes) . ^ . . 38 Carrion Crow (Corrus Corone) 22 



Man (Homo) 34 Tarrock (Larus tridactylus) . 20 



Simia Inuus 30 Green Woodpecker (Picus viri- 



Hystrix cristata 30 dis) 19 



Marmot (Marmota alpina) . . 28 Corvus glandarius 17 



Brown Bear (Ursus Arctos) . . 27 Yellow Oriole (Oriolus Galbula) 16 



Otter (Lutra vulgaris) . ... 26 Psittacus rufirostris . . . . . 11 



Ursus Lotor 25 Virginian Opossum (Didelphis 



Simia capucina 24 virginiana) 20 



Beaver (Castor Fiber) .... 23 Common Squirrel (Sciurus vul- 



Polecat (Mustek Foina) ... 23 garis) 19 



Homed Owl (Strix Bubo) . . 56 Badger (Meles Taxus) .... 19 



Ostrich (Struthio Camelus) . 50 Cavia Cobaya 18 



Golden Eagle (Falco Chrysaetos) 40 Water Rat (Mus amphibius) . 14 



Stork (Ardea Ciconia) ... 33 Hamster (Cricetus vulgaris) . . 12 



Rough-legged Falcon (F. lagopus) 32 Long-eared Bat (Vespertilio auritus) 4 



Buzzard (Falco Bnteo) ... 28 Crossbill (Loxia curvirostra) . 9 



In this table, the larger animals, in general, are those that 

 see farthest. But there are exceptions to this rule. It is worthy 

 of remark, that birds which, in the distinct vision of a point, pre. 



OCTOBEE — DECEMBER 1828. E 



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