June 17, 1922J 



NATURE 



783 



earthwork and outer ditch. Also, within the earth- 

 work there are round patches of chalk. These 

 have been placed theie to mark the sites of holes which 

 were discovered two years ago. We have named 

 them Aubrey holes after an investigator of that name 

 who. in 1666, hinted at their possible existence, but did 

 not find them. Only about half the number has been 

 opened, but we have ascertained that there are fifty- 

 six. They are evenly spaced at 16 feet apart, and 

 there can be little doubt that they once held stones 

 forming a continuous circle, older than the existing 

 monument. The old circle stones would have been 

 rough, undressed ones, and perhaps of about the date 

 of Avebury. When the present monument was built 

 it is possible that the rough stones were taken out and 

 dressed and erected as the smaller stones now visible, 

 as it is not likely they would have been wasted, and, 

 moreover, their number corresponds nearly with that 

 of the holes. 



The empty holes appear to have been used for 

 human interments, as nearly all of them contained 

 cremated bones. Only a portion of the cremated 

 remains of a body are found in each hole and in one 

 instance only fourteen pieces of charred bone. The 

 actual cremations must have been carried out else- 

 where and the remains brought here for interment, for 

 up to the present time no sign of a large fiie has been 

 met with ; and the burning of only one body would 

 require several tons of wood to calcine it thoroughly, 

 and the quantity of black wood ashes remaining, 

 being indestructible, would have been noticed. These 

 interments occurred in Neolithic times, as chips were 

 found amongst the debris in the holes, and in one 



instance an implement maker had thrown all his 

 discarded chips into a hole. 



Lately I have been excavating the ditch outside 

 the earthwork. It was probably the first work 

 done here, and from it I trust to get a continuous 

 linking up of periods from the earliest to the latest. 

 So far this work has not been very profitable, but 

 has given a good result in showing that a very long 

 time must have elapsed between making the ditch 

 and rampart and the building of Stonehenge. It 

 seems to have fallen into neglect, and was nearly 

 silted up when Stonehenge was built. This is con- 

 clusively shown by finding the masons' chips only 

 14 or 15 inches below the surface in the rubble 

 coA-ering the silt, where they cease abruptly, the 

 silt containing no trace of anything relating to 

 Stonehenge. It is devoid of any objects beyond 

 occasional small fragments of animal bone, but when 

 the bottom is reached at 4^ to 5^ feet below the surface, 

 flint chips discarded by implement makers are found 

 in great quantities, but rarely an actual implement. 

 Many staghorn picks used in the excavation of the 

 ditch are met with, and the upper parts of antlers cut 

 off and thrown away when the picks were made. 



'This season I am again excavating the ditch, and 

 this time on the north-east, to find out if it was a con- 

 tinuous circle or whether the avenue was made at that 

 time or later, when Stonehenge was built, for I am 

 inclined to think that there were two distinct periods 

 here — an early one, when the circle of stones stood 

 round the rampart, and a later one when this Stone- 

 henge was built, with a considerable interval between 

 them. 



The Sense of Smell in Birds : a Debated Question. 



sense of touch — witness the bill of the snipe— and 



ORGANS of smell are present in birds as a class 

 and are well developed in many species, but 

 much doubt attaches to the nature and extent of their 

 usefulness. The South American vultures and the 

 petrels are noteworthy for the size of their olfactory 

 chambers, and the Apteryx possesses a complicated 

 nasal labyrinth and is peculiar in having its nostrils 

 at the extreme tip of the beak. Yet even in cases like 

 these the practical demonstration of a sense of smell 

 is beset with difficulties, and the existing evidence is 

 conflicting and largely inconclusive. It seems diffi- 

 cult, of course, to believe that the apparatus serves 

 no purpose, especially where it is highly developed or 

 is specialised along particular lines, but apart from the 

 unsatisfactory quality of a priori arguments the alter- 

 native must be borne in mind that the organs may 

 have some other function than a sense of smell of the 

 kind with which we are subjectively familiar. 



The sense of smell is notoriously acute in the majority 

 of mammals. Although they are generally also well 

 endowed with sight and hearing, it is by smell that 

 .they chiefly find their food and by smell that they 

 receive the first warning of the proximity of enemies : 

 the importance of approaching four-footed game up- 

 wind is a commonplace. In birds the case is obviously 

 very different, for with them vision must certainly be 

 given pride of place. Hearing, too, is very well de- 

 veloped in birds, and there is also often a delicate 



NO. 2746, VOL. 109] 



possibly some power of discriminating food by taste. 

 It may be argued that a sense of smell would be less 

 useful to birds than to mammals : the great distances 

 from which some birds detect their prey seem prac- 

 tically prohibitive for any sense but vision, and the 

 spaces of the upper air must form a much less favour- 

 able medium for scent than the ground winds on which 

 mammals so greatly rely. 



Like so many other problems of natural history, 

 this question attracted the attention of Charles Darwin, 

 and in "A Naturalist's Voyage Round the World " we 

 read of the experiment which he made in a garden in 

 Chile where twenty or thirty captured condors were 

 tethered in a long row at the bottom of a wall. " Hav- 

 ing folded up a piece of meat in white paper," he says, 

 " I walked backwards and forwards, carrying it in my 

 hand at a distance of about three yards from them, 

 but no notice whatever was taken. I then threw it on 

 the ground, within one yard of an old male bird ; he 

 looked at it for a moment with attention, but then 

 regarded it no more. With a stick I pushed it closer 

 and closer, until at last he touched it with his beak ; 

 the paper was instantly torn off with fury ; at the 

 same moment, every bird in the long row began 

 struggling and flapping its wings. Under the same 

 circumstances it would have been quite impossible to 

 have deceived a dog." In the same place Darwin 



