I30 



NA TURE 



[December 9, 1897 



August 1S94, near the Bernina Hospice in Switzerland, I came 

 across several plants of myosotis growing by a pool. In some 

 ■cases the flowers were a bright blue, but in others they were 

 distinctly pink, several being entirely pink, and others showing 

 pink blotches and lines. The plants were in a hollow, and en 

 the day of my visit there was an extremely cold wind blowing. 

 London, December 2. Hector Colwell. 



Fire-fly Light 



Referring to my reply to Prof. S. P. Thompson (Nature, 

 July 29), concerning fire-fly light, I can confirm what then I 

 wrote. Mr. H. Muraoka has sent to me from Kioto in Japan a 

 letter from which I derive the following particulars. ( i ) In the 

 neighbourhood of Kioto there are about nine kinds of Lttciolie, 

 which Mr. H. Muraoka continues improperly to call, in German, 

 Johanniskafern. (2) The insects used by him were probably 

 Lticiola vitlicollis and Luciola picticoUis (Kiesenn). 



Florence, December i. Carlo Del Lungo. 



AN ENGLISH BEA VER PARK. 



SINCE the Marquis of Bute established a colony of 

 beavers on his estate near Rothesay in 1874, no 

 such interesting experiment has been made in acclima- 

 tising these animals as that which Sir Edmund Loder 

 has carried out in Sussex. The beavers have now been 

 inhabitants of his park at Leonardslee, near Horsham, 

 for eight years, or rather they occupy an enclosure 

 inside the park. There they have been placed on 

 the banks of a small stream, with a rather rapid fall, 

 ii situation which exactly suits them. It is sheltered, 

 for the valley is deep and wooded, and there was an 

 ample supply of timber, large and small, in the enclosure 

 when the industrious beavers, reversing the story of 

 ^' Settlers in Canada," were brought from Canada and 

 settled in Sussex. In the course of their eight years' 

 sojourn they have ensured their comfort by constructing 

 in great perfection, and in the most durable form, the 

 engineering works for which beavers are so justly famed, 

 and which gave rise to the Indian legend that the 

 Creator, after separating land from water, employed 

 gigantic beavers to "smooth" the earth into shape. 

 Meantime the colony increases in number, so that some 

 of the produce have been sold to go elsewhere. Never- 

 theless the beavers' industry is such that the size of their 

 works, and consequently the area of the pool which 

 they have formed, constantly increases. 



The space in which they were originally enclosed 

 was less than an acre. This was only one-third of the 

 size of the Marquis of Bute's "beaver park"; but it 

 gave quite sufificient scope for the beginnings of the 

 <;olony. It was surrounded with a corrugated iron fence, 

 which the beavers could not gnaw down, while at the 

 same time they could not see through it, and so felt more 

 secure and " private " in their park. Beaver engineer- 

 ing is directed entirely to one end. This is to form a 

 pool deep enough and wide enough for them to be able 

 to swim beneath the water to the entrance of their 

 burrow, and to keep this entrance submerged in dry 

 weather, when the streams run low, and covered with 

 such a depth of water that even in the longest frosts, 

 when the ice in Northern Canada is two feet thick, 

 there shall still be water-space below it. 



In the water the beaver knows it is safe ; and, though it 

 also stores branches for food below water, fastening them 

 •down with stones and mud, it is to serve as a place of 

 refuge rather than as a storehouse, as a combined moat 

 and temporary hiding-place, that the beaver forms his 

 pool. All his clever engineering, his wood-cutting, 

 building, canal-making and construction of " rolling 

 ways," are subordinate to this end. The two last works, 

 the beaver canal and the beaver road — the one for float- 

 ing, and the other for rolling logs to the pool — are only 



NO. 1467, VOL. 57] 



brought into play when the supply of timber near at 

 hand is exhausted. But they are part and parcel of 

 beaver devices, and, though only recently brought to 

 notice, are not less creditable than their other feats. 



In the present paper we shall not use the technical 

 phrases of hydraulic engineering, but term the reservoir 

 made the " pool," and the containing barrier the " dam." 

 In Canada, when the beavers were numerous, these 

 dams were noticed to be so nicely adjusted in form to 

 the material with which they were made, and to the 

 force of the stream which they barred, that they could 

 be classified in relation to these circumstances. Dams 

 built mainly of mud and stones had a different section 

 from dams built of sand and wood ; and some made 

 across rapid streams were curved, to resist the extra 

 strain. But the greater number were made of battens 

 of wood about three feet long, with the crevices stuffed 

 with mud, stones, and the twigs and small branches ; 

 and in every case the first engineering principle necessary 

 in the construction of a dam is observed. This is that 

 the top shall be exactly level, so that the water of the 

 pool, which must overflow, because the stream enters it 

 from the top end, shall flow evenly over the whole length 

 of the dam. As every one conversant with that most 

 difficult form of the profession— river engineering — 

 knows, any small gap or inequality soon ruins a dam. 

 The water pours through these by preference, and at 

 once cuts a gap. The beavers know this, too, and at 

 Leonardslee, no less than in Canada, constantly examine 

 the top of the dam, and mend the smallest gap along the 

 line. The Leonardslee dam is of the ordinary kind, not 

 curved but straight, and built of battens of wood, made 

 of the boughs from trees cut down inside their enclosure, 

 or from those which were given them as food. Iri all 

 cases they ate most of the bark ; then they cut the sticks 

 into lengths of about three feet, and worked them into 

 the structure. Plenty of mud was pushed into the cre- 

 vices on the upper side, and all the small twigs and 

 sticks were pushed in to make the whole dam tight. 

 With great judgment they spared a small oak growing 

 just below the dam. This now acts as a support to the 

 structure ; all the other trees in the enclosure, except 

 those protected by metal guards, and one very large fir, 

 were either felled, or attempted to be felled. It seems 

 obvious that they kept this tree purposely as a buttress ; 

 for the dam is made higher and, therefore, wider each 

 year, as the pool above increases ; the tree is now almost 

 in the centre, and its roots are already worked into the dam 

 foundations. Even the baby beavers at Leonardslee, no 

 bigger than rabbits, are put to " light jobs " in mending 

 the dam, and the elders are most industrious. Each 

 winter brings down a quantity of mud, which would make 

 the pool shallower. But the beavers raise the dam so 

 rapidly that the pool gains in depth, and spreads for a 

 long distance up stream and laterally. The dam is at 

 least five and a half feet high, and the depth of water 

 above it five feet, yet it is so well made that, though the 

 human-built dams of several artificial pools higher up the 

 stream were carried away in a winter flood, the beaver- 

 dam was undamaged. Near the point at which the 

 stream enters the enclosure three large trees, formerly 

 on the bank, are now submerged in three feet of water, 

 owing to the fresh height added to the barrier below. 

 The beavers had begun to cut these trees down— a very 

 hard task, but one in which they would have suc- 

 ceeded had not the water risen so fast that they were 

 floated off their legs when trying to go on cutting. 

 One large beech tree, standing on a raised bank washed 

 by the ever-increasing pool, was an object of envy to 

 the beavers. They concluded that the quickest plan 

 was not to cut it down, as it was very large and the 

 wood hard, but to dig it up. So, with the aid of the 

 increasing waters, they undermined the tree, which fell 

 across their pool. This gave them occupation for some 



