5 So 



SCIENTIFIC NEWS. 



[Dec. 7, if 



unusual in its frequency, but also unusually complete. 

 In other birds the second moult, where it occurs at all, 

 is partial, a small proportion of the feathers being 

 affected, or some part only of each feather being dis- 

 carded. In the ptarmigan, however, the change is ex- 

 tensive, and concerns nearly all the feathers except the 

 quills of the wing and tail, which are changed only at 

 long intervals. Few adaptations are more familiar or 

 more striking than this seasonal change, which brings 

 about in regular succession a protective resemblance to 

 the brown heather, to the thinly strewn snow, and lastly 

 to the dense snow of a northern mountain. The only 

 Lagopus which undergoes no corresponding change is 

 our own red grouse, a species which would be rendered 

 fatally conspicuous by turning white in winter. 



Those of us who remember the days when the " Origin 

 of Species " appeared will recollect how much was said 

 about that time of the one bird peculiar to the British 

 Isles. Owen, in the British Association Address for 

 1858 (which appeared a few weeks after Darwin and 

 Wallace's preliminary papers), made this fact the text of 

 an interesting though inconclusive discussion, which is 

 now of some historical interest. It marks that change in 

 scientific thought which for the first time forbade men to 

 entertain seriously any such explanation as that the red 

 grouse had been called into existence by a special 

 creative act in and for the British Isles alone. Various 

 writers have referred to a supposed former Continental 

 range of the red grouse, for which bones found in caves 

 and similar remains have been adduced as proof. We 

 are very sceptical as to such identifications, for to dis- 

 tinguish the bones of our native species from those of 

 the Continental willow-grouse would baffle the acutest 

 anatomist. The history of the genus Lagopus, so far as 

 it can be unravelled without light from fossil remains, 

 may be conjecturally restored somewhat as follows : 

 The common ancestor probably resembled in many 

 respects grouse of the genus Tetrao, particularly in not 

 turning white before winter. Our red grouse, by reason 

 of its southern habitat, alone preserves this presumed 

 ancestral peculiarity, and is so far the best surviving 

 representative of the hypothetical common ancestor. 

 Other forms, more or less northerly in range, have 

 developed in a marked degree the seasonal change of 

 plumage. Of these the willow-grouse is most nearly 

 related to our own red grouse, while the ptarmigan, 

 and the closely allied species which inhabit Spitzbergen 

 and Arctic America, are more specialised forms, in which 

 the winter changes are extraordinarily marked. 



The combats for the possession of the females for 

 which the game-cock is so notorious are exemplified in 

 a yet more amusing form by the love-fights of the black 

 cock and the capercaillie. The cocks assemble at well- 

 known spots, where during weeks together they display 

 their charms before the assembled females. The black 

 cock struts, and dances, and beats his wings, and turns 

 round and round in an excitement which at length 

 becomes perfectly frantic. So absorbed are the birds 

 that one after another may be shot, or even caught by the 

 hand, without disturbing the others. When these antics 

 are over the birds begin to fight, and eye-witnesses tell 

 us that the snow may be seen all bloody on the battle- 

 fields of the capercaillie, and that the black cocks make 

 the feathers fly in all directions. In our Scottish pine- 

 woods the excitement seldom reaches such a pitch, 

 perhaps because crowds of birds cannot easily be gathered 

 together, but the capercaillie, or cock of the woods, 



may often be found perched on the top of a high tree, 

 and defying the universe by means of ludicrous noises 

 and gestures, while the awe-struck females wait in 

 silence the result of the engagement which usually ensues. 



&fc$tract$ 

 of papers, Sectureg, tlu 



THE INSTITUTION OF CIVIL ENGINEERS. 

 At the meeting on Tuesday, the 27th of November, the 

 President, Sir George B. Bruce, being in the chair, a 

 paper on " The Witham New-Outfall Channel and 

 Improvement Works " was read by Mr. J. Evelyn 

 Williams, M. Inst. C.E. 



The author stated that in 1878 he was instructed, by 

 the Witham General Commissioners, to report upon the 

 improvement of the river Witham. He then found the 

 Outfall, or tidal portion of the river, most unfavourable, 

 both for drainage and for navigation. A tide which rose 

 21 ft. in Clayhole, in the estuary of the Wash, only rose 

 12 ft. 6 ins. at Boston. The lower reach of the channel, 

 between Hobhole Sluice and the estuary, was not only 

 shallow and circuitous, but untrained and broken through 

 a mass of shifting sands. The flood-waters rushing sea- 

 ward cut frequent and successive " steeps," from 10 to 

 12 ft. in height, which kept tumbling into the channel 

 and choking it up ; the channel thus became distorted, 

 and sometimes shifted a mile from east to west in a few 

 weeks. The flood-tide, from the estuary, swept over 

 these shifting sands, and flowed like a rapid wave up the 

 river to Boston, carrying a large quantity of sand in sus- 

 pension. This was deposited during slack-tide in the 

 upper reach of the outfall, where in dry seasons, during 

 the absence of the fresh-water scour, the deposit reached 

 the level of n ft. 6 ins. above the sills of the Grand 

 Sluice in Boston, and rendered the flow of neap-tides 

 insensible at the sluice. Ultimately it was decided to 

 make a new outfall, and this paper consists of a detailed 

 description of the work, but it is too technical for our 

 columns. 



PHYSICAL SOCIETY. 

 On November 24th, Professor Reinold, President, in 

 the chair, Captain Abney read a paper " On the Mea- 

 surement of the Luminosity of Coloured Surfaces," 

 which was illustrated by experiments. In a communica- 

 tion to the Royal Society General Festing and the 

 author have described a method of comparing the in- 

 tensity of the light of different parts of the spectrum, re- 

 flected by various pigments, with that reflected from 

 white ; and luminosity curves have been constructed, 

 the areas of which give comparative measures of the 

 total luminosities. This method of comparison is accurate, 

 but requires considerable time, and the author has de- 

 vised a more rapid process. The coloured surface whose 

 luminosity is to be compared with white is placed 

 beside a white patch within a dark box. A direct beam 

 of light passes through an aperture in the box, and a 

 black rod casts a shadow on the coloured patch ; another 

 beam from the same source is reflected at an angle, and 

 forms a shadow of the same rod on the white patch, the 

 junction of the two shadows coinciding with that of the 

 two surfaces to be compared. In the path of the direct 

 beam is placed a rotating disc with angular openings, 



