132 



SCIENTIFIC NEWS. 



[Feb. lo, i8 



of the professional human dam-builders who, in the old 

 times, went about erecting water-mills, and it is not 

 surpassed by man even after the widest and most pro- 

 longed experience. 



If they intend to raise the level of the water only a 

 few feet they build on the soil under water just as they 

 find it, trusting to their skill in puddling to stop any leak 

 that may occur. If they wish to raise a high dam, such 

 as will probably be found in places like that which 

 the author is describing, they first clear away all 

 rubbish and loose earth, so as to have a firm, clean 

 foundation for their work. Having thus cleaned out 

 the channel they first drag in poles and large branches, 

 laying the thick or butt ends down stream, and as 

 they raise the pile they draw the timber out, 

 so as to form an "apron " below for the water to fall 

 on, and thus prevent it from undermining the dam. 

 The upper part they furnish with finer woodwork 

 than they have used below. After a sufficiency of 

 this material is thus placed in position, they fill it in with 

 earth, which they carry rolled into balls in their arms 

 pressed against their breasts, and they do not desist 

 until they have made the dam water-tight. They are 

 less particular about the wings of the dam extending on 

 each side of the channel and running from the bed of the 

 stream over the flats to the higher grounds. Here they 

 build on the earth as they find it, since here the 

 pressure and force of the water are not nearly so great 

 as in the actual channel of the river. So cleverly can 

 they stop a leak that the trapper has frequently seen a 

 log laid running through a dam under a head of water of 

 three or four feet, and yet scarcely a drop escaping — a 

 task which, as every dam-builder knows, is very diffi- 

 cult. At a job of this kind they use leaves and moss, 

 and push it in almost as firmly as a caulker does in the 

 seams of a vessel. So firm and substantial is their work 

 that their dams are known to keep full of water for years 

 after all the beavers have been killed off. On one occa- 

 sion the writer saw a dam at the head of a stream where 

 the flow of water in the dry season was so small that 

 evaporation carried it all away, leaving the channel below 

 quite drj-, yet the pool above, thanks to the tightness of 

 the dam, was kept constantly full. If the dam is very 

 high, and the foundation not quite satisfactory, they 

 often build one or more smaller dams below, so as to 

 ease the pressure on the main dam above. The trapper 

 remarks that this peculiar skill of the beaver is " one of 

 the things that stagger Darwin in the belief in his own 

 theory." But can any one suggest a better explanation ? 



Swallows Hybernating. — Mr. John Duncan, of New- 

 castle-on-Tyne, quotes, doubtingl}', the following story : — 

 "An English traveller and his escort, proceeding to 

 Teheran, the modern capital of Persia, in winter, travelled 

 through a pass where there had been an extensive land- 

 slip, owing to the frost. Hundreds of swallows, very 

 similar to our British house martins, were found amongst 

 the debris. These birds were in a torpid condition, but 

 when taken into the hand, and exposed to the vivifying 

 influence of the camp fire, they all recovered, and, 

 though the weather at the time was severe, most of them 

 rallied and were able to fly away, after being thawed at 

 the fire." Mr. Kerr, of Bacup, writing the same paper, 

 gives, on the authority of a Shrewsbury correspondent, 

 ■ a notice of a torpid swallow whick he had found " one 

 winter," and which revived on being warmed. Mr. 



Duncan asks for particulars of this case, and remarks 

 that several alleged instances of the hybernation of 

 swallows have been recorded, but on being carefully 

 tested they could not be substantiated. 



The Senses of Insects. — M. A. Ford {Rectteil Zoolog. 

 Sttisse and American Naturalist) gives the following sum- 

 mary of the observations of himself and others. In 

 regard to the sight of ants, he finds that they per- 

 ceive light, and especially the ultra-violet rays ; they 

 really see these rays, as when without eyes they are 

 almost indifferent to them. On smell he concludes that 

 the insects which are essentially guided by sight, as 

 dragon-flies and cicadas, have rudimentary antennae and 

 little sense of smell. During the night these insects are 

 torpid, and during the day they trust to sight — the cicadas 

 perhaps also to hearing. The organ of smell is situate 

 in the antennae, especially in those parts where the 

 antennary nerve ramifies. As distinct organs of taste 

 Forel regards the nervous terminations on the proboscis 

 of flies, on the jaws, and on the base of the tongue, on 

 the end of the tongue, and on the palate or the epipharynx. 



A Whale in the Channel. — The captain and crew 

 of the barge Fiances, of London, reported at Dover hav- 

 ing seen a whale of extraordinary dimensions in the 

 English Channel on Monday, the 30th ult., about eight 

 miles off the South Foreland. The crew of the Frances, 

 who were corroborated in their statements by the crew 

 of the Maud Little, belonging to Rochester, who also saw 

 the monster, state that their vessel passed within 150 

 yards. When they first saw it both crews mistook it 

 for the .hull of a large vessel which had capsized. The 

 whale measured from 80 to 100 feet in length, and was 

 travelling through the water in an easterly direction, at 

 a good speed, spouting up the water to a distance of 

 about 60 or 70 feet. The fins on the monster's back 

 were about 14 feet above the water. — Times. 



Winter Diet of Birds. — A correspondent of the New- 

 castle Clirotiicle, writing from Matfen in Northumberland, 

 states that during the snow-storms at the beginning ot 

 January he hung part of the remains of a goose on a 

 currant-bush in the garden, which the blue and the great 

 tits speedily polished to a fine skeleton. The fieldfares, 

 which have been very abundant since November, cleared 

 off the heavy crop of holly-berries, which they preferred 

 to the haws. They have also consumed large quantities 

 of yew berries, which are reputed to be poisonous. 

 Wood-pigeons are plentiful in the turnip fields, but, 

 though they feed upon the leaves and shoots, they do not, 

 as it was formerly suspected, eat the roots. Rooks, how- 

 ever, if pressed for food in severe weather destroy the 

 bulbs. 



Post-Glacial Insects. — Mr. Alfred Bell offers some 

 suggestions in the Entomologist for January about post- 

 Glacial insects. So far as his experience goes, insect 

 remains are by no means common, and belong chiefly to 

 the Coleoptera. He gives nearly thirty species, nearly 

 all of which belong to this division of the insect world. 

 As Mr. Bell points out, however, it does not follow that 

 Lepidoptera were not present during the post-Glacial 

 period, since they occur in beautiful preseryation in 

 deposits of a much older date in England and on the 

 Continent. The nature of the post-Glacial soils was not 



