others like some owls and flycatchers have emarginate primaries but do not soar.Professor Trowbridges comparison of the wing to a flat card is hardly felicitous and his statement that it would be in a scate of unstable equilibrium but for the locking of the primaries would seem open to serious doubt.One absolute requisite of a wing is that the anterior margin should be rigid and the posterior border flexiblea requirement which is met toward the extremity of a birds wing by bringing the quill close to the radial margin of the feather leaving a posterior pliable edge.Now if the primaries are interlocked a rigidity is created toward the ulnar border of the wing which would thus become more cardlike and unserviceable than if the primaries did not lock.A pertinent question that might be asked of Professor Trowbridge is Why if the long primaries present a serious resistance . when a bird is soaring do all birds that soar or sail possess just such primaries while the corresponding feathers in birds which do not soar are short?One feature in the wings of birds pre-eminent for soaring abilities e.g the Vulturidaand Falconidahas not been touched upon in this discussion so far as I am aware; and this is the fact that when the wing is extended to its utmost as it invariably is during soaring the metacarpus and phalanges are not in line with the ulna but are bent forward of it. By this arrangement some of the muscles Coach Outlet Store Online and tendons that Nike Australia ordinarily act in flexing the wing are brought upon the dorsal surface of the bones and thus have their power of flexion weakened or possibly even made to aid in the automatic extension of the wing. If now a bird with wings thus Nike Air Max 90 spread be so killed that there is no perceptible shock or nervous start the bird may remain with outstretched pinions and sail gradually downward exactly such a case as Professor Newberry describes.In conclusion I can but regret that I have no facts to adduce that will throw any light on the problem of flight as it is far easier to find fault with any theory than to suggest a better and purely adverse criticism must Coach Outlet Store Online always seem more or less ungracious.FREDERICA. LUCAS.Wellington D.C Jan. .Binocular Combinations upon Disparate Retinal Points. EVERYone is familiar with the fact that Wheatstone and many subsequent investigators have explained the binocular perception of solidity by the theory of the fusion of images upon disparate points as they are called in the retina. They have generally denied the original possibility of a monocular perception of solidity and distance; and hence when certain plane figures were stereoscopically combined the apparent solidity of the resulting single figure suggested Christian Louboutin Outlet its explanation in accordance with what had previously been supposed of the mathematical Nike Air Max relation between combination and convergence. Thus Wheatstones view may be illustrated by the following figure. It is well known that the stereoscopic combination of these figures although making a plane image only upon the retina and representing only a plane surface externally nevertheless produces the appearance of a solid body. Previous theories of vision had maintained that single vision took place upon correFrc. .sponding points of the retina and double vision upon disparate points. Now as the mathematical construction of the case would not allow the inner figures and lines to fall upon exactly corresponding points the apparently single character of the Nike Shoes Australia image in stereoscopic combination was most naturally explained by saying that fusion took place upon disparate points ; and hence when the perception of solidity or relatively different distances between the larger and smaller figures uniformly accompanied this kind of fusion it was naturally ascribed to that process as its cause. Whether such a fusion really takes place or not has been hotly contested Coach Outlet Store Online and we wish here to present a few new considerations to show that it does not occur notwithstanding the strongest apparent evidence Christian Louboutin Outlet of our actual