December 9, 1897] 



NATURE 



131 



weeks. They ate every morsel of bark off the trunk and 

 branches, and then cut off the boughs, gnawed them into 

 lengths, and took them to the dam and to their " lodge." 

 The latter began as a burrow in the bank. As they 

 gradually enlarged this, and filled up the bottom with 

 wood chips, they broke open the roof to get head room, 

 and constantly added to the dome with mud and sticks. 

 It is now a large untidy mound on the bank, which at 

 this point is steep. 



The process described above accounts partly for the 

 evolution of the beaver lodge from the burrow. But the 

 keeper of Lord Bute's beavers stated that the beavers at 

 Rothesay did clean out the old shavings which they took in 

 to make beds of, and plastered them on the outside of 

 their lodge, or on the same embankment. The present 

 writer inclines to believe that this is likely to be correct, 

 not in every case, but in some, for it is very much in 

 keeping with beaver character. In such cases he ven- 

 tures to offer the following solution of the growth of the 

 lodge, in cases where the beavers remove their bedding 

 of chips. The water above the dam, owing to the causes 

 mentioned above, rises higher yearly. This must also 

 raise the level in the sub-aqueous passage leading to the 

 beavers' chamber, and in time tend to invade the chamber 

 itself. To remedy this the beavers would naturally raise 

 the floor, and leave the debris of old " beds " on it, 

 piling fresh stuff on the top, and at the same time quarry 

 out the roof, both for head-room and to get fresh 

 earth for their floor. When once the artificial roof was 

 made the same process would go on, until the rising 

 water flooded out the floor altogether, and surrounded 

 the lodge, as one sees it in old Canadian pictures. The 

 lodge would thus take the beehive, moated, form which 

 it has in those conventional plates, even though it lacks 

 the windows which the French artists added for effect. 

 The beavers occasionally escape by burrowing under the 

 corrugated iron fence. This is not always intentional 

 on their part, and they are easily caught again. When- 

 ever one gets out it travels up the stream, visiting the 

 pools above. There a box-trap is set next night, baited 

 with dog-biscuit, of which the beavers are fond, and the 

 animal is certain to be caught. One beaver, out for a 

 stroll like this, tried to cut down a large Scotch fir, and 

 did cut down a silver birch. The first indication to the 

 keeper next morning that a beaver had escaped was the 

 sight of this tree, in full leaf, lying across a path. 



We mentioned above that the Leonardslee beavers 

 had not made either a canal or a rolling path. There is 

 no need for either ; for there are no more trees to cut 

 down, or logs to roll from a distance. But it is worth 

 devoting a few lines to these, two of the less known, but 

 not least extraordinary exhibitions of beaver intelligence. 

 An old-established colony soon clears off all the timber 

 near its home. In order to convey the more distant logs 

 to the dam they carefully clear paths, and roll the 

 battens of wood down to the water. But the 

 beaver canal, to which proper attention was first 

 drawn by Mr. Lewis Morgan, is, in the writer's opinion, 

 more wonderful still. It is nothing more nor less 

 than a waterway, or several waterways cut from points 

 on the stream to such parts of the adjacent plantations 

 or woods as the beavers wish to visit, or cut timber in. 

 Sometimes, also, it is made through the centre of an 

 island, to make short communication by water. To this 

 canal the beavers roll their logs, and then tow them to 

 their dam. It has been urged that these canals are 

 accidental, merely worn out along the customary roads ; 

 some are, no doubt. But wherever the writer has seen 

 tame beavers kept, even at the London Zoo, he has seen 

 them at different times cut trenches to the edge of their 

 pool, though as that at the Zoo was surrounded by a 

 stone rim, the beavers could not fill the trench with 

 water. Of course, there this trench was only a few feet 

 long. But it is quite clear that Lord Bute's beavers, 



NO. 1467, VOL. 57J 



which had a considerable area in which to cut their 

 timber, tried to dig canals. This is the description giver» 

 by their keeper, who, though well acquainted with beaver 

 stories, evidently had never heard of the canal. " Their 

 burrows they make by cutting a road from the middle of 

 the dam for several yards into the dry ground, where 

 they scoop out a dome-shaped burrow. . . . Some of 

 the roads to these burrows are from fifteen to twenty 

 yards long, and so level that the water follows them in 

 the whole length " I Here is, undoubtedly, an instance 

 of the beaver canal. 



Those who care to compare the methods of the 

 Canadian beavers acclimatised at Leonardslee with the 

 works and ways of the European beavers still surviving 

 in Norway, will find an interesting account of the past 

 and present history of the Norwegian beaver, by Mr. R. 

 CoUett (" Bieveren i Norge"),^ illustrated with twelve 

 plates of beaver lodges and dams, and supplemented by 

 an English summary. 



The beavers' present range is confined to the Stifts of 

 Christiania and Christiansand, but a few remain on 

 Bratsberg Amt and Stavanger Amt. The larger colony 

 is on the River Nisser (or Nid), the westernmost colonies 

 being on the river Mandal. In all cases they feed 

 not on fir, but on deciduous trees, mainly the aspen. 

 When not on the banks of large rivers they make 

 dams, one of which, near Hellersli (Trungen), was 

 built entirely in three weeks, and formed a lakelet more 

 than 100 yards across. The length of the dam was 

 14 metres. In only one respect do the habits of the 

 Norway beavers differ from those of the Canadian 

 species. Those that live on the banks of the large rivers 

 cannot make a dam over such rapid and deep waters. 

 Yet these rivers rise and fall, and there is a danger of 

 the lodge being either flooded or left high and dry. In- 

 these places the beavers build long lodges, at right angles 

 to the stream, and sloping up the bank. When the river 

 rises, the beaver can go up to the higher end of his lodge ;. 

 when it falls, the entrance is still submerged and safe. 



In 1880 Mr. Cocks estimated the number of beavers 

 surviving in Norway at 60 ; in 1883 Mr. CoUett believes 

 there were 100. Since 1894 and 1895 the beavers have 

 been protected by law in their two principal haunts, for a 

 period of ten years in each district. 



C. J. Cornish. 



SCIENTIFIC INVESTIGATIONS OF THE 

 LOCAL GOVERNMENT BOARD? 



THE Annual Reports of the Medical Officer of the 

 Local Government Board constitute in many 

 respects the best treatise on practical hygiene we possess. 

 Their diligent perusal by the embryo health officer would 

 equip him as no ordinary text-book can do for the intel- 

 ligent discharge of his duties. It would be well if can- 

 didates for Public Health degrees were examined upon 

 the salient features of these reports. The volume for 

 1895-96, which has just been issued, contains certain 

 features of interest. There is the usual admirable 

 summary of the year's work by Sir Richard Thome ; 

 statistics with regard to vaccination, and a compilation 

 of returns of notified infectious diseases in urban 

 districts and in the county of London. Valuable reports 

 are also contributed by Dr. Copeman and Dr. Buchanan 

 upon outbreaks of enteric fever, and by Dr. Sweeting 

 upon an outbreak of diphtheria. The able report by the 

 late Mr. R. W. Thomson upon the sewerage and drainage 

 arrangements of certain valleys in the counties of Mon- 

 mouth and Glamorgan, leads one to join in the regret 

 expressed at the loss of this talented official. It is, hovir-' 



J Bergen: Grieg's " Bogtrykheri." 



2 Twenty-fifth Annual Report of the Medical Officer of the Local 

 Government Board, 1895-96. 



