March 24, 1893 J 



SCIENCE. 



161 



most highly organized birds, as the Passeres, the aftersbaft is 

 very weak, and in many peculiarly specialized birds, as the owls, 

 American vultures, ospreys, and kingfishers, it is wholly wanting. 

 The second reason for considering it primitive is the process of its 

 development during the formation of the feather. It is needless 

 to republish here the history of a feather's growth, but it may be 

 well to call attention to one or two points. When the malpighian 

 layer covers the feather-papilla, it would naturally be thinnest on 

 the sides. The increased thickness above and below would cause 

 greater pressure on the papilla along the median line on both 

 surfaces, thus causing the grooves in which the rhachis and hypo- 

 rhachis subsequently develop. Now, it is known that both these 

 grooves occur in those feathers which have an aftershaft, and it 

 is much more probable that, though now the upper groove is the 

 larger, they wereoriginallyof equal size, than that the lower groove 

 is a secondary development; because it is difficult to assign any 

 possible reason for its ever beginning at all as a secondary charac- 

 teristic. The foregoing facts give warrant to the following theory 

 of the evolution and subsequent degeneration of the aftershaft. 



Paleontology shows us that flight was an accomplished fact 

 long before birds were evolved, and, since it requires tremendous 

 muscular energy, it would be an obvious advantage to the hypo- 

 thetical avian ancestor to decrease his weight and, at the same 

 time, increase the non-conductability of his covering. When, 

 therefore, feathers were first evolved from scales, the object in 

 view was increase of heat-retaining power combined with decrease 

 of weight. The most natural way of improving scales in this 

 direction would be to make them thicker and. at the same time, 

 hollow, and continued development along this line vvould result 

 in making them more or less quill like. Then by dividing longi- 

 tudinally and at right- angles to the axis of the body the number 

 would be doubled without taking up any more space on the body, 

 an obvious advantage. Constant suhdivision, making them more 

 adjust-ible, more coherent, and more compact, would finally bring 

 about a condition very similar to that of the down-reathers of 

 many birds especially in the first plumage. From this con- 

 dition it is not diflicult to trace the gradual development into 

 a contour-feather in which shaft and aftershaft are of equal 

 size, such a condition, in fact, as we find in the Cassowaries. 

 But in this condition the feathers cause far too great friction 

 with the air to admit of rapid flight, and so there came about the 

 natural evolution of the more coherent, pennaceous feather with 

 its comparatively smooth surface. But the natural curve of the 

 lower half of this primitive feather was up and outwards and in 

 direct antagonism to the down and inward curve of the main 

 shaft, and so, being a hindrance to the required compactness, it 

 gradually gave way and degenerated to its present condition. The 

 rest of the story has already been told ; how, where the aftershaft 

 has adapted itself to its sole function as heat-retainer, it is stiU 

 strong and useful, but in all other cases it is either wholly lost or on 

 the rapid road thereto. Whether subsequent investigations and dis- 

 coveries in paleontology and histology confirm this theory remains 

 to be seen, but, for the present, it is at least plausible and open to 

 few objections. 



BRITISH STONE CIRCLES." 



BY A. L. LEWIS, LONDON, BNGLANn. 



No. I. — Abury. 



The largest circle of stones in the world was that of which the 

 remains — few when compared with the magnitude of the struc- 

 ture of which they formed part, but by no means inconsiderable 

 in themselves — are to be seen at Abury, in Wiltshire. Abury 

 village is six miles from Marlborough station (Great Western 

 Railway); it occupies the site of the circles and is mainly built of 

 fragments of the stones which composed them. The monument 

 when complete consisted of a circle of one hundred stones (more 



1 It has been tbouglit that many Americans who, when In England, visit 

 Stoaehenge may not be aware bow many remains of a similar character, 

 which they might also wish to inspect, exist in the British Isles ; and the editor 

 of Science has accordingly made arrangements for a series of short articles, 

 which shall give a description of each of the principal circles and state what 

 points should be noted and how it may most easily be visited. 



or less), of which thirteen still remain above ground and at least 

 sixteen more are buried, some of these are of great size, more 

 bulky than any at Stonehenge, but unshaped and without the 

 cross-pieces which distinguish the latter monument from all other 

 circles. The diameter of this circle was about eleven hundred 

 feet, or eleven times that of the outer circle at Stonehenge; inside 

 it were two other circles, — north and south, — both over three 

 hundred feet in diameter. Dr. Stukeley considered that there was 

 a smaller circle inside each of these, but there is now nothing 

 remaining of them, and it has been doubted whether they ever 

 existed. In the centre of the northern inner circle there were 

 three very large upright stones, forming a "cove'' or three sides 

 of a square, of which the open side was toward the northeast, 

 and of these stones two still remain, besides which there are now 

 only three stones of the northei-n inner circle or circles and five of 

 the southern, and a single stone, which Stukeley said stood in the 

 middle of the latter, has long since disappeared. The total num- 

 ber of stones composing the inner circles, " cove," etc., was, ac- 

 cording to Stukeley. eighty-nine. 



The circles (and the greater part of the village) are surrounded 

 by a deep ditch, outside which is a high embankment. Aubrey, 

 the first writer who noticed this monument, made a very imper- 

 fect plan of it in 1663, in which he represented an avenue of 

 stones leading down in a straight line to the present main road, 

 near the River Kennet, and another avenue of stones leading from 

 the end of it, also in a straight line, but at a right-angle, to a 

 smaller circle on Overton Hill, near the line of large barrows 

 which crosses the main road from Marlborough before it reaches 

 the point where the road to Avebury leaves it. Stukeley deline- 

 ated these as one avenue running in a curved line about a mile 

 long between the great circles at Abury and the smaller one on 

 Overton Hill, and thought that it represented a serpent, of which 

 the Overton Hill circle formed the head, and the Abury circles 

 some convolutions of the body, the tail being represented by 

 another avenue, which left the great circles near where the 

 church now stands, and curved away to the left, passing two large 

 stones called the "long stones," which are still to be seen," though 

 of the rest of the alleged second avenue nothing remains in situ, 

 so that some archseologists think it never existed, especially as 

 Aubrey, who visited the circles more than fifty years before 

 Stukeley. has not left any notice of it. Stukeley, however, spent 

 much more time at Abury than Aubrey did, and obtained much 

 information from the inhabitants as to the former position of 

 stones which had been destroyed within their remembrance, and, 

 as there is much stone used in causeways, etc., over the marshy 

 ground on that side of Abury, it is probable that an avenue of 

 some sort did formerly exist there, but this a point for the visiter 

 to investigate for himself. 



The circle on Overton Hill and the end of the avenue adjoining 

 it were destroyed before Stukeley went to Abury, but there are 

 several stones of the other part of the avenue standing and fallen 

 by the side of the road which leads from the main road at West 

 Kennet to Abury village, and in a meadow under the left-hand 

 hedge of the main road there are four fallen stones of the avenue, 

 and. as these follow the curve which the road makes between the 

 barrows and the turn to Abury, they seem to show that Stukeley 

 was right in delmeating a single curved avenue in place of the 

 two, meeting at right angles, which Aubrey shows in his plan. 

 This is another point for the visitor to verify, and he will do well 

 to follow the avenue from these four stones to its junction with 

 the circles at Abury, and, having inspected the latter, to go out 

 past the church to the " long stones," and to the Beekhanipton 

 Inn, which is on the main road by which he will return to Marl- 

 borough, stopping on his way to climb Silbury Hill, the largest 

 artificial mound in Europe. This attracts attention by its regular 

 shape and flattened top, and, as it is due south from the circles 

 at Abury, probably formed part of the monument; it has been 

 dug into, but nothing has been found to show it to be a sepulchral 

 mound, like the smaller barrows which are so numerous in this 

 district. Human remains were found round the Overton circle, 

 but none are known to have been found at Abury, so that it does 

 not appear that the object of these circles was, as some suppose, 

 2 These are probably the last survivors of another large circle. 



